NORTHWESTERN UNIVERSITY The Voice of Experience: Causal … · 2020-06-16 · A DISSERTATION...

NORTHWESTERNUNIVERSITY

TheVoiceofExperience:CausalInferenceinPhonotacticAdaptation

ADISSERTATION

SUBMITTEDTOTHEGRADUATESCHOOLINPARTIALFULFILLMENTOFTHE

REQUIREMENTS

forthedegree

DOCTOROFPHILOSOPHY

FieldofLinguistics

ByThomasDenby

EVANSTON,ILLINOIS

June2019

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Abstract

Successfullygrapplingwiththewidespreadlinguisticvariationofdailyliferequires

speakerstoadapttosystematicvariationintheenvironmentwhilediscardingincidental

variation,basedontheirpriorexperience.Inthecaseofphonotactics,speakers’prior

experienceisthattalkerswhodifferintheirlanguagebackgroundarelikelytovaryintheir

phonotacticgrammars,whiletalkerswhosharealanguagevarietyareunlikelytodoso.As

such,wepredictthatwhenspeakersareexposedtomultipletalkerswhosephonotactics

vary,andthosetalkersdifferintheirlanguagebackground,listenerswillinferthevariation

issystematicandadapt.Conversely,ifthetalkerssharealanguagebackground,listeners

willinferthevariationisincidental,andnotadapt.

InStudy1,wetestedthispredictioninaperceptionexperiment,byexposing

listenerstotwotalkers,eachofwhomexhibitedadifferentphonotacticconstraint,ina

recognitionmemorytask.InExperiment1,whenlistenerswereexposedtotalkerswho

differedintheirlanguagebackground(1Englishvs.1Frenchtalker),theyshowedahigh

degreeofadaptation;whenthetalkerssharedalanguagebackground(2Englishor2

Frenchtalkers),listenersshowedalow-to-moderatedegreeofadaptation.InExperiment2,

weexaminedthegranularityoflistenerknowledgeofvariationinnon-nativephonotactics

byincludinganovelconditionwithtwonon-nativetalkers(1Hindivs.1Hungariantalker).

Listenersshowedahighdegreeofadaptationevenwhenbothtalkerswerenon-native

speakerswithdifferentlanguagebackgrounds,suggestingthatlistenersmakedistinctions

betweendifferentnon-nativelanguagephonotactics.

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InStudy2,weexaminetheroleofcausalinferenceinspeechproduction.Recent

worksuggestsadaptationinproductionmaydifferfromperception,asproductionmay

utilizesimpleassociativelearningmechanismsthatmaynottakehigh-levelindexical

featuresintoaccount.Weexplorethisquestionusingamodifiedtonguetwisterparadigm,

inwhichparticipantsrepeatsyllablesequencesfromtwomodeltalkers,witheachtalker

exhibitingadifferentphonotacticconstraint.MirroringStudy1,modeltalkerseither

sharedanon-nativelanguagebackground;sharedanativelanguagebackground;or

differedintheirlanguagebackground(thelanguagesbackgroundsinquestionwere

GermanandEnglish).Inaddition,acontrolconditionwasincludedfollowingprevious

tonguetwisterexperiments,inwhichthephonotacticconstraintwasconditionedonthe

identityoftheadjacentvowel.Resultswerelargelyinconclusive—therewassomeevidence

ofincreasedadaptationwhenparticipantswereexposedtomodeltalkerswithdifferent

languagebackgrounds,buttheeffectwasinconsistent.Inaddition,noeffectwasfoundin

thecontrolcondition.

Together,theseresultssuggestthatphonotacticadaptationisflexible,but

constrainedbythecausalinferenceslistenersdrawfromtheirpriorexperience,

particularlyinperception.

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Acknowledgements

It’shardtolookbackoverthelastsixyearsandadequatelyputintowords,oreven

fullyaccountfor,theprofoundhelpmyfriends,family,andcolleagueshavegivenmetoget

tothispoint.I’lldomybest.

Firstandforemost,I’dliketothankmyadvisorandmentor,MattGoldrick.It’sbeen

anhonortoworkwithyou,andIfeltsoprofoundlyluckysoofteninmygraduatecareerto

haveyourexpertguidance,calmdemeanor,andinfinitewisdominmycorner.You’rea

modelofwhatagoodmentor,teacher,andresearchershouldbe,andIfeelsothankfulto

havehadthatmodelthroughoutgradschool.I’llmissourmeetings,spentuntangling

knottyideasandmakingobscureSimpsonsreferences.Iwouldnotbetheresearcherand

thinkerIamwithoutyourhelp,norwouldthisdissertationhavebeenpossible.Thankyou

foreverything.(AndsorryaboutallthosedeadlinesImissed…)

ThankyouAnnBradlowandJenniferCole,mycommitteemembers,foryour

expertiseandcriticaleye.Youeachconsistentlychallengedmyassumptionsinawaythat

mademethinkmoredeeplyaboutmywork.Yourexperienceandacumenmadethe

dissertationstronger,andyourencouragementandpositivitybuoyedmyspiritsalongthe

way.

ThankyoutotheNationalScienceFoundation,fortheirgenerousfundingand

support(grant#1728173).

ThankyoutothemembersofSoundLab,pastandpresent,whoheardmetalkabout

thisworkinitsvariousformsfor5yearsandprovidedinvaluablefeedbackalongtheway

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(andlistenedtomecomplainabouthand-codingspeecherrorseveryweek).Specialthanks

tolabmembersEmilyCibelli,ErinGustafson,NicoleMirea,andMariaGavinoinparticular

foryouradvice,support,andfriendship.ThankyoutoallofmyfellowLinggradstudents

overtheyears,fortheircamaraderieandsupport.

ThankyoutoChunChan,whosetechnicalwizardryandabilitytosolvedifficult

logisticalproblemsmadehugeportionsofthisprojectpossible.Thankyoualsotothemany

brilliantlinguistswhogavemeadviceandideasfornovelconditionsalongtheway,

especiallyMelissaBaese-BerkandGaryDell.

ThankyoutoKatHall,mycohort-mate,confidant,andbestbud.Takingthisjourney

withyouhasbeenoneofthegreatjoysofmylife.Youweremyrockthroughoutgraduate

school,andhangingoutwithyouneverfailedtofillmewithjoyandappreciationforwhata

strong,brilliant,andsillypersonyouare.ToSean,thankyouforyourcompanionship,your

warmth,andyourendlessgoodness.YouandKat(andAbbeyandMiles!)aremyChicago

family,andIloveyou.

Thankyoutomyothercohort-mateNayounKim,forbeingtheperfectofficebuddy

andalwayssupportingmeinthetoughesttimes.I’llalwaysthinkbackonourgiggly,

punch-drunkdaysinSwift309spentagonizingoverourdissertationswithfondness.

ThankyoutomymanyChicagofriendsforkeepingmesane,healthy,andhappy

overthelastsixyears.ToLaura,John,andTaylor,forbeingmyfavoritestdrinkingbuddies

andgenerallythemostrefreshing,comforting,wonderfulhumanbeingsinChicago.To

Libby,forbeingwithmethroughalltheupsanddowns(#sadnesstwinsforever).Tothe

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foundingmembersofTatLPD(EmilyCibelli,AngelaCooper,ErinGustafson,CindyBlanco,

JulieMatsubara),I’llmissourjamsessions.

ThankyoutoBriannaKaufmanandAlexKapelman,mylong-distancebestbros,who

supportedmeandletmeblowoffsteamcountlesstimesonthephone.Youarethetruest

friendsIcouldeveraskfor.

Thankyoutoallfourofmyparentalunits.ToMomandDad,mywordswilldono

justicetowhatyouhavegivenme,butheregoes.Thankyouforalwaysbeingthereforme,

alwayssupportingmeandmyeducation,alwayslendingmeanempatheticear.Thankyou

forstokingmyintellectualcuriosity,forteachingmehowtowriteandthinkcritically,for

pushingmetodomore,andforpickingmeupwhenIfall.Mostofall,thankyoufor

kindness,andforyourlove.ToJanetandSusan,thankyouforbeingthemostwonderful,

supportive,andaffectionatestepparentsIcouldeveraskfor.Iamfilledwithgratitudethat

youbothcameintomylife,andIknowI’msmarter,kinder,andmoreopenbecauseofit.

Finally,thankyoutomypartnerCassandraRose,whohasbeenbymysideforevery

upanddownofthisproject(andthereweremany).Youspentendlesshourssittingonthe

couchwithmewhilewebothclackedawayonourlaptops,supportingmywork,listening

tomekvetch,andboostingmyspiritswithfrequentboutsofextremesilliness.Your

patienceandyourgoodnessandyourkindnessareunlimited.YouarethebestpersonI

know,andIamsoluckytohaveyouinmylife.IloveyouandIlikeyou.

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TableofContents

ABSTRACT.................................................................................................................................................2

ACKNOWLEDGEMENTS........................................................................................................................4

TABLEOFCONTENTS............................................................................................................................7

LISTOFFIGURES..................................................................................................................................11

LISTOFTABLES...................................................................................................................................13

1. INTRODUCTION...........................................................................................................................15

2. STUDY1..........................................................................................................................................22

2.1. INTRODUCTION...........................................................................................................................................................22

2.2. BACKGROUND.............................................................................................................................................................27

2.2.1. Phonotactics........................................................................................................................................27

2.2.2. AdaptationandVariation.............................................................................................................29

2.2.3. PhonotacticAdaptationandVariation...................................................................................31

2.3. EXPERIMENT1A........................................................................................................................................................33

2.3.1. Participants.........................................................................................................................................37

2.3.2. Stimuli....................................................................................................................................................38

2.3.3. Procedure.............................................................................................................................................39

2.3.4. Design.....................................................................................................................................................40

2.3.5. DataAnalysis......................................................................................................................................41

2.3.6. Results....................................................................................................................................................43

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2.3.7. Experiment1ADiscussion.............................................................................................................45

2.4. EXPERIMENT1B........................................................................................................................................................48

2.4.1. Participants.........................................................................................................................................49

2.4.2. Stimuli....................................................................................................................................................49

2.4.3. DataAnalysis......................................................................................................................................50

2.4.4. Results....................................................................................................................................................51

2.4.5. Discussion.............................................................................................................................................52

2.4.6. Experiment1conclusion................................................................................................................54

2.5. EXPERIMENT2...........................................................................................................................................................55

2.5.1. Participants.........................................................................................................................................57

2.5.2. Stimuli....................................................................................................................................................57

2.5.3. Procedure.............................................................................................................................................59

2.5.4. Design.....................................................................................................................................................59

2.5.5. DataAnalysis......................................................................................................................................60

2.5.6. Results....................................................................................................................................................62

2.5.7. Discussion.............................................................................................................................................63

2.6. LISTENERLANGUAGEBACKGROUNDANALYSIS...................................................................................................65

2.7. GENERALDISCUSSION...............................................................................................................................................68

2.7.1. PhonotacticsandL2Acquisition................................................................................................70

2.7.2. AccentDetection................................................................................................................................72

2.8. CONCLUSION...............................................................................................................................................................73

3. STUDY2..........................................................................................................................................74

3.1. INTRODUCTION...........................................................................................................................................................74

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3.2. BACKGROUND.............................................................................................................................................................77

3.2.1. Phonotacticlearninginspeechproduction..........................................................................77

3.2.2. Causalinferenceinphonotacticadaptationinproduction............................................79

3.2.3. CurrentStudy......................................................................................................................................81

3.3. METHODS....................................................................................................................................................................84

3.3.1. Participants.........................................................................................................................................84

3.3.2. Materials...............................................................................................................................................85

3.3.3. Procedure.............................................................................................................................................88

3.3.4. Analysis..................................................................................................................................................89

3.4. RESULTS......................................................................................................................................................................90

3.4.1. Discussion...........................................................................................................................................102

3.4.2. Production-perceptiondynamicsandphonotacticadaptation.................................107

3.5. CONCLUSION............................................................................................................................................................108

4. CONCLUSION..............................................................................................................................110

4.1. STUDY1....................................................................................................................................................................111

4.2. STUDY2....................................................................................................................................................................115

4.3. FUTUREDIRECTIONS..............................................................................................................................................117

4.4. CONCLUSIONS..........................................................................................................................................................122

5. APPENDIX...................................................................................................................................123

5.1. APPENDIXA–STUDY1VOWELACOUSTICSANALYSIS....................................................................................123

5.2. APPENDIXB–STUDY1PILOTSTUDY.................................................................................................................125

5.3. APPENDIXC–STUDY1POWERANALYSIS.........................................................................................................127

5.4. APPENDIXD–STUDY1PASSINGRATES............................................................................................................128

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5.5. APPENDIXE–STUDY1MODELRESULTS...........................................................................................................134

5.6. APPENDIXF–TONGUETWISTERSAMPLESIZEANALYSIS..............................................................................136

5.7. APPENDIXG–STUDY2MODELRESULTS...........................................................................................................138

5.7.1. Within-conditionmodels;allsessions;[m]-[n]swapsincluded..................................138

5.7.2. Within-conditionmodels;[m]-[n]swapsexcluded..........................................................139

5.7.3. Within-conditionmodels;session1excluded;[m]-[n]swapsexcluded..................140

6. REFERENCES..............................................................................................................................142

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ListofFigures

Figure2.1.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment1A.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment1A.Inbothpanels,errorbarsreflectbootstrapped95%confidenceintervals...........................................................................................................................................................44

Figure2.2.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment1B.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment1B.Inbothpanels,errorbarsreflectbootstrapped95%confidenceintervals...........................................................................................................................................................51

Figure2.3.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment2.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment2.Inbothpanels,errorbarsreflectbootstrapped95%confidenceinterval..............................................................................................................................................................................62

Figure3.1.Overallerrorratesbyparticipant.Colorsreflectexperimentalcondition...........92Figure3.2.Percentageoferrorsthatmaintaintheirsyllablepositionforconstrainedvs.

unconstrainedconsonants,brokendownbysessionandcondition.Alldatavisualized,including[m]-[n]swaps.Errorbarsreflect95%confidenceintervaloverparticipant;however,notethatparticipantscontributeddifferentnumbersoferrorstoeachbar.96

Figure3.3.Percentageoferrorsthatmaintaintheirsyllablepositionforconstrainedvs.unconstrainedconsonants,brokendownbysessionandcondition.[m]-[n]swapswereexcluded.Errorbarsreflect95%confidenceintervaloverparticipant;however,notethatparticipantscontributeddifferentnumbersoferrorstoeachbar.IntheVowelcondition,oneparticipantmadethemajorityoftheerrorsbuthadamuchlowermeanthanotherparticipants,resultinginaCIthatdoesnotoverlapwiththemeanforSession1,unconstrainederrors............................................................................................................99

Figure5.1.ScatterplotoffemaleFrenchtalkers’firstandsecondvowelformants.Eachpointisavowel,withvowelidentityindicatedbytheappropriateIPAsymbol.Colorindicatestalkerdifferences...................................................................................................................124

Figure5.2.Scatterplotofhitrate(%yesonfamiliaritems)ingeneralizationphasebylegalityadvantage(falsealarmrateforlegalitemsminusfalsealarmrateonillegalitems)forallexperimentsinStudy1.Eachdotrepresentsasingleparticipant;colorsrepresentwhetherparticipantspassedorfailedcriteria.LinesrepresentLoessregression;shadingrepresents95%confidenceinterval.......................................................130

Figure5.3.LegalityadvantageforExperiment1A,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval......................................................132

Figure5.4.LegalityadvantageforExperiment1B,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval......................................................132

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Figure5.5.LegalityadvantageforExperiment2,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval......................................................133

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ListofTables

Table2.1.SummaryofconditionsinExperiment1A,alongwithexperimentalspeakerlanguagebackground,gender,andstimulusvowels.NotethatvirtuallyalllistenerswerenativeEnglishspeakers.................................................................................................................35

Table2.2.SummaryofconditionsinExperiment2,alongwithexperimentalspeakerlanguagebackground,gender,andstimulusvowels.NotethatvirtuallyalllistenerswerenativeEnglishspeakers.................................................................................................................56

Table3.1.Summaryofconditions,alongwithmodeltalkerlanguagebackground,vowels,gender,anddegreeofadaptation.........................................................................................................84

Table3.2.Numberoferrorsanderrorratesbycondition..................................................................92Table3.3.Target/errormatrixforallconsonantsandconditions.Targetsarecolumnsand

errorsarerows.TheNoTargetcolumnreferstoerrorsthatweremadeonextrasyllables(i.e.,whenaparticipantproducedmorethan4syllablesinasingletwister).Gradientcolor-codingreflectsthenumberoferrorsforagiventarget/errorcombination...................................................................................................................................................94

Table3.4.Betweenconditioncomparison;allsessions;[m]-[n]switchesincluded...............97Table3.5.Betweenconditioncomparison;session1excluded;[m]-[n]switchesincluded98Table3.6.Differentcondition;session1excluded;[m]-[n]switchesexcluded.......................100Table3.7.Betweenconditioncomparison;allsessions;[m]-[n]switchesexcluded.............101Table3.8.Betweenconditioncomparison;session1excluded;[m]-[n]switchesexcluded.

...........................................................................................................................................................................101Table5.1.PassingratesforeachconditionandexperimentinStudy1......................................129Table5.2.Experiment1AFixedEffects.....................................................................................................134Table5.3.Experiment1Arandomeffects................................................................................................134Table5.4.Experiment1Bfixedeffects.......................................................................................................134Table5.5.Experiment1Brandomeffects.................................................................................................135Table5.6.Experiment2fixedeffects..........................................................................................................135Table5.7.Experiment2randomeffects....................................................................................................135Table5.8Numberofitemsanalyzed(wordsorsyllables),errors,errorrates,andconstraint

orderforprevioustonguetwisterexperiments..........................................................................137Table5.9.Differentcondition;allsessions;[m]-[n]swapsincluded............................................138Table5.10.NativeSharedcondition;allsessions;[m]-[n]swapsincluded..............................138Table5.11.Non-NativeSharedcondition;allsessions;[m]-[n]swapsincluded....................139Table5.12.Vowelcondition;allsessions;[m]-[n]swapsincluded...............................................139Table5.13.Differentcondition;allsessions;[m]-[n]swapsexcluded........................................139Table5.14.NativeSharedcondition;allsessions;[m]-[n]swapsexcluded..............................140Table5.15.Non-NativeSharedcondition;allsessions;[m]-[n]swapsexcluded....................140Table5.16.Vowelcondition;allsessions;[m]-[n]swapsexcluded..............................................140Table5.17.Differentcondition;session1excluded;[m]-[n]swapsexcluded.........................141Table5.18.NativeShared;session1excluded;[m]-[n]swapsexcluded...................................141

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Table5.19.Non-NativeSharedcondition;session1excluded;[m]-[n]swapsexcluded....141Table5.20.Vowelcondition;session1excluded;[m]-[n]swapsexcluded...............................141

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1. Introduction

Inourday-to-daylivesweencounteranenormousamountoflinguisticvariation.

Individualspeakers,forexample,widelyvaryintheirvowelproductions(e.g.,Hillenbrand,

Getty,Clark,&Wheeler,1995).Successfullynavigatingsuchwidespreadvariationrequires

ustoquicklyandeffectivelyadapt—i.e.,updatingourexpectationstobettermatchfuture

inputinagivencontextbasedonwhatwearecurrentlyexperiencinginthatcontext,soas

tobetterpredictandmoreefficientlyprocessfutureevents.1Inthecaseofphonetics,this

involvesadaptingtonovelspeakers,dialects,languages,andothertask-relevantproperties

thatservetodistinguishdifferentcontexts.Suchflexibilityiscriticaltoourabilityto

accuratelyperceivespeechfromdifferentspeakersandindifferentenvironments,aswell

ashaveourspeechbeaccuratelyperceivedbyothers.Thetypeofvariationweencounteris

notrandom,however—itishighlystructured,withindividualspeakers,dialects,languages

andcontextsallvaryingindifferentwaysandtodifferentdegrees(Kleinschmidt&Jaeger,

2015).Uncoveringtheunderlyingstructurethatgeneratesdistinctpatternsofvariationis

criticaltosuccessfuladaptation.Todoso,speakersmustusetheirpriorexperiencewith

variationasaguide,makingcausalinferencesaboutthesourceofvariation.Doingso

allowsspeakerstoadapttosystematicandrelevantvariation,whileignoringincidental

1Wedifferentiateshorter-termadaptationfromlonger-termlearningprimarilybasedonthedifferenttimecoursesforeachprocess.

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variationnotrelevantforthetaskathand(Liu&Jaeger,2018;Samuel,Brennan,&Kraljic,

2008).

Forexample,ifsomeonehearsatalkerconsistentlyproduceanidiosyncratic[s]that

soundsunusuallylike[ʃ](e.g.,shickinsteadofsick),adaptingtothatspecificindividual’s[s]

productionswillbeadvantageousforperceivingthatindividual’sspeechinthefuture,asit

isastablepropertyoftheindividualspeaker.Thisisaformofsystematicvariation,guided

bythelistener’spastexperiencewithindividualphoneticvariation(e.g.,Kraljic&Samuel,

2007).If,ontheotherhand,thespeakerhappenstohaveapenintheirmouthwhile

talking,thelistenercaninferthatthesourceoftheidiosyncratic[s]productionmaybedue

toanincidentalfactor:theobstructionfromthepen.Thisincidentalvariationisunlikelyto

bepredictiveofthespeaker’sfuturespeechinothercontexts(i.e.,whentheydonothavea

penintheirmouth);assuch,listenersarelesslikelytoadaptundertheseconditions(Liu

andJaeger,2018;Samueletal.,2008).Critically,listenersdonotcompletelydisregardall

causallyambiguousinput(i.e.,idiosyncraticproductionswhenthetalkerhasapenintheir

mouth).Instead,theyholditinmemory,asitmaybepredictiveoffutureinputinsimilar

contexts(i.e.,futureproductionswhenthetalkerhasapenintheirmouth)oritmayprove

tobepredictiveafterfurtherdisambiguatingevidence(i.e.,thetalkerproducesthesame

idiosyncraticproductionswithoutapenintheirmouth;Liu&Jaeger,2018;Kraljic&

Samuel,2011).Inotherwords,adaptationrequireslistenerstoproperlyattributevariation

toitsunderlyingsourceforthegiventask.

Inthisdissertation,wewillfocusontheroleofsystematicvs.incidentalvariationin

adaptationtonovelphonotacticconstraints.Phonotactics—constraintsonthepossible

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sequencesandpositionsofsoundswithinwordsandsyllables—differwidelybetween

languages,butmuchlesssobetweenindividualspeakersofasinglelanguagevariety.

English,forexample,allowsvoicedplosives(i.e.,[b],[d]and[g])insyllable-finalposition;

Dutch,ontheotherhand,onlyallowsvoicelessplosivesinsyllable-initialposition.While

suchphonotacticdifferencesbetweenspeakersofDutchandEnglisharesystematic,

encounteringtwoEnglishspeakerswhodifferinthiswayisunlikely.Thereare

communicativeconstraintsagainstwidespreadphonotacticvariationbetweenspeakers

withinlanguagevarieties,asindividualspeakersdifferinginthiswaywouldleadto

unreliablecuestowordandsyllableboundaries,resultinginfrequenterrorsinlexical

access(Pierrehumbert,2001).

Theunderlyingstructureofphonotacticvariation,andspeakers’previous

experiencewiththisvariation,likelyplaysaroleinthewaysspeakersadapttonovel

phonotacticconstraints.Researchoverthepast20yearshasfoundthatspeakersquickly

adapttonovelphonotacticconstraints(e.g.,“[s,ʃ,f]arerestrictedtoonsetposition,while

[p,t,k]arerestrictedtocodaposition”)inbothspeechproduction(e.g.speecherror

patterns;Dell,Reed,Adams,&Meyer,2000)andperception(e.g.memoryerrorpatterns;

Bernard,2015).

Inthisdissertation,weexplorethehypothesisthatphonotacticadaptationis

constrainedbythetypesofcausalinferencesspeakersmakeaboutthesourceof

phonotacticvariation.Thesecausalinferencesarebasedonspeakers’priorexperience

withphonotacticvariation:speakersofdifferentlanguagessystematicallydiffer,often

quitedrastically,intheirphonotactics;whilespeakersofthesamelanguagevarietiesare

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unlikelytovaryinthisway.Assuch,wepredictthatwhenlearnersencountersuch

variationbetweenspeakersofasinglelanguagevariety,theywillinferitisincidental,

ratherthansystematic.Inotherwords,theywillnotattributethesourceofthevariationas

beingadurable,context-independenttraitofthetalker.Thishypothesispredictsthatwhen

speakersareexposedtomultipletalkerswithdistinctphonotacticgrammars,eitherin

perceptionorproduction,theywillshowahighdegreeofadaptationifthosetalkersclearly

differintheirlanguagebackground(e.g.,onenativeHinditalkerandonenativeEnglish

talker),andalowdegreeofadaptationiftheydonot(e.g.,twonativeEnglishtalkers).

Indeed,theonlypreviousstudytoexamineadaptationtoindividualtalkerswhosharea

languagevariety(e.g.“TalkerAdoesn’tendtheirsyllablesin/f/;TalkerBdoesn’tendtheir

syllablesin/n/”)foundthatspeakersdidnotadaptundertheseconditions,usinga

speededrepetitiontask(Onishi,Chambers,&Fisher,2002).

Thesepredictionsaretestedintwostudies.Study1examinesphonotactic

adaptationinperception,exposinglistenerstotwotalkers,eachofwhomdiffersintheir

phonotacticgrammar(e.g.,“forTalkerA,[s,ʃ,f]arerestrictedtoonsetposition;forTalker

Bwhile[p,t,k]arerestrictedtocodaposition”).Crucially,insomeconditionsthetalkers

differintheirlanguagebackgrounds;inotherconditions,thetalkerssharealanguage

background.Adaptationisassessedviaarecognitionmemoryparadigm(e.g.,Bernard,

2015;Denby,Schecter,Arn,Dimov,&Goldrick,2018).InExperiment1,listenersare

exposedtonativeFrenchandEnglishtalkersexhibitingdifferentphonotacticconstraints.

Wepredictthatwhenlistenersareexposedtotalkerswithasharedlanguagebackground

(i.e.,2Englishtalkersor2Frenchtalkers)theywillinferthetalkerssharealanguageand

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thereforeasinglephonotacticgrammar,suggestingthephonotacticvariationisincidental,

andshowalowdegreeofadaptation.Whenlistenersareexposedtotalkerswhodifferin

theirlanguagebackground(i.e.,1Englishtalkerand1Frenchtalker),wepredictlisteners

willinferthevariationisasystematicqualityofthetalkers’languages,andtherefore

listenerswillshowahighdegreeofadaptation.

Resultsshowedthatlistenersadaptedtothenovelconstraintsinallconditions,

suggestingthattheyattendedtothedifferingphonotacticsevenwhenthesourceof

variationwascausallyambiguous(i.e.,talkerssharedalanguagebackground).Thehighest

degreeofadaptationoccurred,however,whentalkersdifferedintheirlanguage

backgrounds,andthelowestdegreeoccurredwhenbothtalkerswerenativespeakers.In

otherwords,listenersadaptedtoahigherdegreewhenthesourceofthevariationwas

causallyunambiguous(i.e.,talkersdifferedintheirphonotacticsduetothedifferencein

theirlanguagebackgrounds).Surprisingly,listenersadaptedtoamoderatedegreewhen

bothtalkerswerenon-native(i.e.,Frenchtalkers).Thismaybeduetolisteners’lackof

knowledgeofnon-nativelanguages—listenersarelikelymoreconfidentjudgingtwonative

talkersasspeakingthesamelanguagethantwonon-nativetalkers.

HowcanweunderstandlistenerbehaviorinExperiment1?Listenersmaysimplybe

sensitivetowhethertheysharethelanguagebackgroundofatalker(native)orifthetalker

doesnotsharetheirlanguagebackground(non-native).Alternatively,listenersmaybe

sensitivetotalkerlanguagebackgroundsregardlessofwhethertheythemselvessharea

backgroundwiththetalker.InthesecondexperimentofStudy1,weinvestigatethe

structureoflistenerknowledgeofnon-nativephonotacticvariation.Listenersareexposed

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totalkersoftwonon-nativelanguages(HindiandHungarian).Iflistenersmakedistinctions

withinnon-nativephonotacticgrammars,theyshouldadaptwhentalkersdifferintheir

languagebackgrounds.If,ontheotherhandlistenersonlydistinguishbetweennativevs.

non-nativephonotactics,withoutfurtherdistinctionsbetweennon-nativephonotactics,

theywillinferbothnon-nativespeakersshareasinglephonotacticgrammarandshowa

smalldegreeofadaptation.Resultssuggestedlistenersweresensitivetodistinctions

withinnon-nativelanguages:listenersadaptedtoahighdegreewhentalkersdifferedin

theirlanguagebackgrounds,regardlessofwhetheroneofthemwasnative(e.g.,English

talkervs.Hinditalker)ornot(e.g.,Hungariantalkervs.Hinditalker).

InStudy2,weexaminewhetherspeakersmakecausalinferencesaboutphonotactic

variationinspeechproduction,usingamodifiedtonguetwisterparadigm(Dell,etal.,

2000).Participantsareexposedtomultiplemodeltalkers—nativeEnglishand/ornative

Germantalkers—exhibitingdistinctphonotacticconstraints.AsinStudy1,thesemodel

talkerseitherdifferintheirlanguagebackgroundsorshareasinglelanguagebackground;

wepredictahighdegreeofadaptationwhenmodeltalkersdifferintheirlanguage

background,andalowdegreeofadaptationwhenmodeltalkerssharealanguage

background.Recentevidencefromphonotacticadaptationinproduction,however,points

toapurelyassociativeaccountofphonotacticadaptationinproduction(e.g.,Anderson,

Holmes,Dell,&Middleton,2019),inwhichinferencesaboutthecausesofvariationarenot

alwaysintegratedintoadaptation.Assuch,itispossiblewemayfinddivergentresultsin

studies1and2duetobroaddifferencesinadaptationinspeechperceptionandproduction

(e.g.,Samuel,2011).

21

ResultsfromStudy2weredifficulttointerpretgivenasurprisinglyhighnumberof

illegalerrors,acrossallconditions,fortheconsonantsthatwerethetargetofthe

constraint.Despitethis,thereissomeevidenceofadaptationwhenmodeltalkersdiffered

intheirlanguagebackground,butnoevidenceofadaptationwhenmodeltalkersshareda

languagebackground.

Together,thesestudiesaimtoextendtheoriesoftheroleofcausalinferencein

adaptationintothedomainofphonotactics;explorepossibledifferencesinadaptation

betweenperceptionandproduction;andshedlightonthemechanismsunderlyingthe

speedandflexibilityofphonotacticadaptation.

22

2. Study1

2.1. Introduction

Listenersencounterahugeamountofvariationintheirday-to-daylinguistic

experience—forexample,men,womenandchildrenshowconsiderablevariationintheir

vowelproductions(e.g.,Hillenbrand,Getty,Clark,&Wheeler,1995)—andyetspeech

perceptionisremarkablyaccurate.Overthelast25years,theimportanceoflistener

adaptationtonoveltalkershascomeintofocus:forexample,whenlistenersareexposedto

idiosyncraticproductionsofspeechsounds,theyareabletoadapttheirphonemiccategory

boundariesaccordingly,anddosodifferentlyfortalkerswithdifferentproductions(e.g.,

Kraljic&Samuel,2007).Thisadaptationallowslistenerstonavigatetheinter-talker

variabilitytheyencounter,helpingthemtopredictspeechfromthattalkerinthefuture.

Theflexibilityofperceptualadaptation,however,isconstrainedbythetypesof

highlystructuredvariationlistenersencounter—individualtalkersdonotvaryfreely.

Beyondidiosyncraticdifferencesbetweenindividuals,talkersvaryonanumberof

linguisticandsociolinguisticdimensions(e.g.,nativevs.nonnativetalkers,dialect,age,

race;seeDrager,2010forreview).Forlistenerstousethisstructuredvariationtotheir

advantageinperception,theymustidentifythesourceofthevariation,andtheunderlying

systemthatgeneratesit(e.g.,Kleinschmidt,2018;Kleinschmidt&Jaeger,2015).Indoing

so,speakersmustdistinguishbetweensystematicvariationthatisrelevantforagiventask,

andincidentalvariationthatisirrelevantforthetask(e.g.,Kraljic&Samuel,2011;Kraljic,

Samuel,&Brennan,2008;Liu&Jaeger,2018).

23

Forexample,imagineyouarehavingaconversationwithsomeonewhohasabad

cold.Thechangestothatspeaker’svocaltractfromthecold(e.g.,occlusionofthenasal

tract)introducedistortionstotheacousticpropertiesoftheirspeech(e.g.,Tull,Rutledge,&

Larson,1996).Theacousticdistortionintroducedbythecoldistemporary,andnot

systematicforthatspeaker—itisnotapartofthespeaker’susualstate,andthusnotuseful

forperceivingthattalker’sspeechinthefuture.Ifyouencounterthisspeakeragainina

week,it’slikelythatthisacousticdistortionwillnolongerbepresent.Assuch,listeners

shouldputlittleweightonthoseproductionswhenupdatingtheirexpectationsofthat

talker’sfuturespeechwhenhealthy.Thisconstitutesoneofthecorechallengesofspeech

processing:adaptingtosystematicandrelevantvariation(e.g.,talkerdifferences)thatwill

helpyoubettercommunicateinthefuture,whiledeemphasizingirrelevantandincidental

variation(e.g.,noisyproductions)2.

Inthisstudy,weexaminethetypeofrelevantvs.irrelevantvariationspeakers

experiencewithregardstophonotactics—constraintsonpossiblepositionsandsequences

ofsoundsinwordsandsyllables—andhowthesystematicityofvariationaffects

adaptation.Englishspeakers,forexample,unconsciouslyknowthatsung[sʌŋ]isa

phonologicallylicitstructurebutngus[ŋʌs]isnot,as[ŋ]canonlyappearinsyllable-final

positioninEnglish(e.g.,Chomsky&Halle,1965).Phonotacticconstraintsdiffer2Itshouldbenotedthatwhilethephoneticvariationintroducedbythecoldisirrelevantforguidingfutureexpectationsaboutthatparticulartalker,itishighlyrelevantforsimilarcontextsencounteredinthefuture:namely,whentalkershavecolds.Assuch,wemightexpectthatlistenersbuildamentalrepresentationof“coldspeech”,reflectingthestructureofphoneticvariationtheyexperience,thatallowsthemtobettercomprehendsuchspeechinthefuture.

24

systematicallybetweenlanguages:unlikeEnglish,Vietnameseallows[ŋ]inonsetposition,

aswellascoda(e.g.,[ŋũ],“sleep”).Suchdifferencesbetweenlanguagesarecommon:

Russianallowsconsonantclusterssuchas[stv]thatarenotlegalinEnglish;Dutchdoesnot

allowvoicedobstruents,suchas[d],attheendsofwords;Hawaiiannotallowany

consonantsincodaposition;andsoon.

Twoindividualspeakersofasinglelanguagevariety,however,generallydonot

differinthisway—sharingaphonotacticgrammarispartofwhatitmeanstosharea

languagevariety.Forexample,encounteringanativeEnglishspeakerwhosegrammar

allows[ŋ]inonsetpositionisexceedinglyunlikely.Moreover,Pierrehumbert(2001)

arguesthatphonotacticconstraintsmustbewidelysharedacrosstalkerswithinalanguage

forcommunicationtobepossible:ifspeakersofasingledialectsystematicallyvariedin

theirphonotacticgrammars,phonotacticcuestowordandsyllableboundarieswouldbe

unreliable,leadingtosystematicerrorsinlexicalaccess.(Forexample,itcanbedifficultto

tellwordsapartinspeechfromanunfamiliarlanguage,dueinparttoalackofknowledge

ofthatlanguage’sphonotacticcuestowordboundaries.)

Assuch,thereisasystematicasymmetryinthedegreetowhichphonotactic

constraintsvarybetweenspeakersofdifferentlanguagesandspeakerswhosharea

languagevariety.Forexample,anEnglishspeakerandaFrenchspeakerwillvaryintheir

phonotacticgrammarsmuchmorethantwoEnglishspeakerswhosharetheInlandNorth

dialect.Weexaminehowthesesystematicdifferencesshapeadaptationtonovel

phonotacticconstraints.

25

Overthepasttwodecades,laboratoryparadigmshavebeendevelopedthatallowus

toexamineadaptationtovariationinphonotactics.Thesestudiessuggestthattalkersand

listenersadapttonovelphonotacticswithsurprisingspeed:participantsareabletolearn

arbitraryconstraints(e.g.,[n]and[f]cannotappearincodaposition)inbothspeech

production(e.g.speecherrorpatterns;Dell,Reed,Adams,&Meyer,2000)andperception

(e.g.memoryerrorpatterns;Bernard,2015;Denby,Schecter,Arn,Dimov,&Goldrick,

2018).

Wehypothesizethat,muchliketheexamplesofperceptualadaptationdiscussed

above,listenersadapttorelevantorsystematicphonotacticvariation,whileignoring

variationirrelevanttothetaskathand.Unliketalker-specificphonetics,however,

phonotacticsvarylittlebetweenindividualspeakerswithinaspeechcommunity.This

suggeststhatlistenersmaytreatdifferencesbetweenindividualtalkersasirrelevant,and

inferasingle,sharedphonotacticgrammarfortwotalkerswhoshareadialect.Indeed,one

studythatinvestigatedtalker-specificphonotacticconstraints(e.g.,forFred,stopsare

restrictedtocodaposition,andfricativesareunconstrained;viceversaforBarbara)foundno

evidenceofadaptation(Onishi,Chambers,andFisher,2002).Extendingpreviousfindings,

wepredictlittleadaptationwilloccurwhenspeakerssharealanguageevenifboth

speakersarenon-native(relativetothelistener).Inotherwords,whetherthespeakers

shareanativelanguagewiththelistenerisimmaterial—aslongasthespeakerssharea

languagewithoneanother,listenersshouldinferthetwospeakersshareaphonotactic

grammar,andthereforenotadapt.

26

Inaddition,thecomplementarypredictionhasyettobeexamined.Whenlisteners

encounterphonotacticvariationbetweentwospeakerswhodonotsharealanguage

background(e.g.,anativespeakerofEnglishvs.anativespeakerofFrench),wepredict

theyshouldtreatsuchdifferencesassystematicbasedontheirpriorexperiencewith

phonotacticvariationacrosslanguages,andinferseparatephonotacticgrammarsforeach

speaker.

Itisunclearwhattypeanddegreeofexperiencewithnon-nativelanguagesis

requiredtomakeinferencesaboutspeakerlanguagebackgroundandphonotactic

variation.It’spossiblethatlistenersonlyrequireoccasional,incidentalexposuretonon-

nativephonotactics(fromeitherspeakersofdifferentlanguages,oraccentedspeakersof

theirnativelanguage).Manylistenerswouldnaturallycomeacrosssuchspeechintheir

dailylivesinanindustrializedsocietysuchastheUnitedStates(MechanicalTurkworkers,

whichisthepopulationwesampledfrom,alsohavehigherratesofeducationthanthe

generalU.S.population;Levay,Freese,andDruckman,2016).Alternatively,listenersmay

requireahighdegreeofexposure,suchashavingspenttimelearninganon-native

language,orproficiencyintwoormorelanguages.Toaddressthisquestion,weanalyzethe

self-reportedlanguagebackgroundsofourlisteners.

Thisstudyconsistsoftwosetsofartificialgrammarexperimentsinwhichnative

Englishlistenersareexposedtotwotalkers,eachofwhomexhibitsadifferenttalker-

dependentphonotacticconstraint.Crucially,thelanguagebackgroundoftalkersis

manipulated.InExperiments1AandB,talkerssharealanguagenativetolisteners(2

Englishtalkers);shareanon-nativelanguage(2Frenchtalkers);ordonotsharealanguage

27

background(1Frenchtalker,1Englishtalker).Wepredictthatlistenerswilladaptonly

whentalkersdifferintheirlanguagebackground,aslistenersinferfromtheirprior

experiencethatlanguage-dependentvariationisrelevant,whilewithin-dialectvariationis

incidental.Topreviewtheresults,wefinddifferencesinthedegreeofadaptation,rather

thanthecategoricalpresencevs.absenceofadaptation,basedonsharedordifferenttalker

languagebackgrounds.Thisleadsustorefineourhypothesis:listenersadapttoagreater

degreetovariationtheyinterpretasrelativelysystematic,andtoalowerdegreeto

variationtheyinterpretasrelativelyincidental.

InExperiment2,weexaminethestructureoflistenerknowledgeofvariationinnon-

nativephonotactics.Listenersmaybesensitiveonlytowhetherornottheysharea

languagebackgroundwiththetalker,distinguishingonlybetweenthelistener’snative

languageandallnon-nativelanguages.Alternatively,listeners’priorknowledgecould

makedistinctionsbetweenmultiplenon-nativelanguages.Toexplorethisquestion,

listenersareexposedtonon-nativetalkerswhodifferintheirlanguagebackgrounds(1

Hinditalker,1Hungariantalker).

2.2. Background

2.2.1. Phonotactics

Knowingthephonotacticsofalanguageentailsknowingrealwordsinthatlanguage

(e.g.,Englishflick),aswellaswhatconstitutespossiblewords(frick),andwhatconstitutes

impossiblewords(fnick;Chomsky&Halle,1965).Thisknowledgeguidesperceptionin

28

profoundways,asiteliminatessomeoptionsaspossiblewordsbutnotothers.For

example,MassaroandCohen(1983)findthatthesametoken,ambiguousbetween[r]and

[l],isperceiveddifferentlybasedonthelegalityofthephonotacticcontextinwhichit’s

heard:inthe[t?i]context,it’smoreoftenperceivedas[r];inthe[s?i]context,it’smore

oftenperceivedas[l].Phonotacticsalsoinfluenceswordsegmentation(firstlanguage:

McQueen,1998;secondlanguage:WeberandCutler,2006),andanumberofother

perceptualprocesses(e.g.,Dupoux,Kakehi,Hirose,Pallier,&Mehler,1999;Otake,

Yonehama,Cutler,vanderLugt,1996;Pitt&McQueen,1998;Vitevitch&Luce,1999;fora

review,seeGoldrick,2011).

Giventheimportanceofphonotacticsinpredictionprocesses,anefficientlearner

shouldquicklyadapttonovelphonotacticconstraintstobetterguideperceptioninthe

future.Indeed,listenerscanquicklylearnartificialphonotacticconstraintsinexperimental

settings(e.g.,Bernard,2015;Denby,etal.,2018;Onishietal.,2002;Richtsmeier,2011;

Steele,Denby,Chan,&Goldrick,2015).Bernard(2015),forexample,exposedparticipants

toaseriesofspokensyllablesexhibitinganexperimentalconstraint(e.g.,[p]cannotappear

incoda;[f]cannotappearinonset).Participantswereaskedaftereachsyllablewhether

theyhadheardthatsyllableearlierintheexperiment.Afteranumberofrepetitionsofthe

exposureset,ahandfulofnovelsyllableswerepresented,halfofwhichfollowedthe

constraintandhalfofwhichviolatedtheconstraint.Participantsweremorelikelytofalse

alarmonnovelsyllablesthatfollowedtheconstraintthanthosethatviolatedit,suggesting

participantswereutilizingthenovelconstrainttomakememoryjudgments.

29

2.2.2. AdaptationandVariation

Theguidingroleofpriorexperienceisageneralpropertyofadaptation.Inthe

perceptionoffaces,forexample,learnersadaptdifferentlytonovelfaceshapesthatare

similarvs.dissimilartofacestheyhavepreviouslyexperienced(e.g.,Little&Apicella,2016;

Webster,Kaping,Mizokami,&Duhamel,2004),suggestingthatthetypeofvariation

learnershavepreviouslyexperiencedaffectshowtheyadapttonovelpatterns.Similarly,in

theadaptationtothephoneticsofindividualtalkers(e.g.,Creel,Aslin,&Tenenhaus,2008;

Eisner&McQueen,2005;Goldinger,1996;Kraljic&Samuel,2007;Nygaard&Pisoni,1998;

Pardo,2006),adaptationismotivatedbythehugeamountofinter-andintra-speaker

phoneticvariationspeakershavepreviouslyencountered(e.g.,Hillenbrandetal.,1995).

NygaardandPisoni(1998),forexample,foundthatlistenersmoreaccuratelyrecognized

wordsandsentencesinnoiseforfamiliartalkers,suggestingtheylearnidiosyncratic

featuresofthattalker’sspeechandusethatknowledgetoguideperceptionofthattalkerin

thefuture.

Inadditiontoadaptationtovariationbetweenindividualtalkers,adaptationis

conditionedonthestructuredvariationintroducedbyhigher-level(socio)linguisticfactors

(e.g.,Kleinschmidt,2018).Asubstantialbodyofworkhassuggestedthatlistenersencode

thisstructuredvariation(seeDrager,2010,forreview).Inturn,thesefactorsguide

adaptationtonovelspeakers,mostclearlyinthecaseofnon-nativeaccentadaptation

(Bradlow&Bent,2008;Reinisch&Holt,2014;Xie&Myers,2017).Forexample,fornative

Englishlisteners,exposuretoSpanish-accentedtalkersimprovesrecognitionaccuracyfor

30

novelSpanish-accentedtalkers,especiallyforwordsincludingSpanishvowelsthatareless

characteristicofEnglish(Sidaras,Alexander,&Nygaard,2009).Thissuggestslisteners

havemodelsofspecificnon-nativeaccents,encodedasdistinctfromnativeaccents,and

usethisinformationtoguideadaptation.Thereisalsoevidencethatinsomecontexts

nativelistenerstreatnon-nativespeechasadistinctconcept,astheyareabletogeneralize

acrossnon-nativeaccents(Baese-Berk,Bradlow,&Wright,2013).

Listenerscanalsousepastexperiencewithphoneticvariationtomakecausal

inferencesaboutthesourceofthevariationforthenovelexperimentaltalkersand

contexts.Kraljic,Samuel,andBrennan(2008)exposedlistenerstoatalkerproducing

ambiguous[s~ʃ]productions.Inonecondition,listenersheardtheambiguousproductions

inanexposurephasewithavideodepictingthetalkerwithapenintheirmouth;ina

secondcondition,listenerswereexposedtothesametalker,butwithavideodepictingthe

talkerholdingthepenintheirhand.Thepeninthemouthconditionprovidedlisteners

withanincidentalsourceforthevariation:thepeninthetalker’smouthwasdisrupting

theirproductions.Assuch,listenersdidnotadapttothetalker’sidiosyncratic[s~ʃ]

boundaryinthatcondition.Listenerswhosawthevideoofthetalkerwiththepenintheir

hand,however,inferredthatthevariationtheywereexposedtowasasystematic

characteristicofthattalker’sspeech,andadaptedaccordingly–appropriatelyutilizing

previousexperiencetoconstrainadaptation(seealsoKraljic&Samuel,2011;Liu&Jaeger,

2018).

Recentworkintherationallearnerframeworkhascharacterizedresultssuchas

thesebyviewingadaptationasprocessofuncoveringtheunderlyingstructurethat

31

generatesobservableeventsandinferringcausalrelationsthathelptoexplainthoseevents

(Qian,Jaeger,andAslin,2012).Suchmodelsofhowtheworldworksallowgeneralization

tonovelsituations—priorexperiencecanguideexpectationsaboutwhatwillbe

encountered,especiallyinsimilarcontexts,andhelpmakesenseofnovelexperiences.

Priorexperiencecanalsoconstrainadaptation,whenthenovelcontextisdissimilarto

thosewehaveexperiencedpreviously.Thisrigidityisanimportantfeatureofthesystem,

astotalplasticitywouldrequireinefficientlybuildinganentirelynovelmodelforevery

novelcontext.Withinthisframework,thestructuredvariabilitythatformsthebasisofour

experiencewithlanguageisencodedviaahierarchicalindexicalstructure(Kleinschmidt&

Jaeger,2015;Pajak,Fine,Kleinshmidt,&Jaeger,2016).Forexample,listenerscouldmodel

structuredphoneticvariationbyincludingdifferentlanguagesatthetopofthehierarchy

(e.g.,Hindi,French),withnativevs.non-nativeaccentsonestepbelow,followedbydialects

withinthenativeaccentandsociolinguisticgroupings(e.g.,gender),withindividual

speakersatthebottom.

2.2.3. PhonotacticAdaptationandVariation

Iflistenersbuildahierarchicalindexicalstructurebasedonthevariationthey

encounter,suchastructureshoulddifferforlevelsoflinguisticstructurethatexhibit

differentpatternsofstructuredvariation.Giventhatphonotacticvariationisgreatest

32

acrosslanguagesandsmallestacrossindividuals3,wehypothesizethatlistenerswill

assumethattheyshouldbuildseparatemodelsforspeakersofdifferentlanguages,while

theywillassumethatspeakerswithinadialectshouldbeassignedtothesamemodel.This

hypothesispredictsthatlistenersshouldshowagreaterdegreeofadaptationtotalker-

specificphonotacticswhenthetalkersdifferintheirlanguagebackground.

Thispredictionisconsistentwithevidencefrompreviousphonotacticadaptation

studies,inwhichlistenersareexposedtoartificiallanguageswithnon-nativephonotactic

constraints,andappeartoquicklylearnthesenovelconstraints,suggestingthatlisteners

assumetheyhaveencounteredanon-native“laboratorylanguage”.Indeed,participantsare

abletomaintainseparatemodelsforEnglishandalearnedlaboratorylanguage.Ina

productiontask,Warker(2013)exposedparticipantstocomplex,“second-order”

phonotacticconstraints,inwhichthepossiblepositionsofaphonemedependonfeatures

ofsurroundingphonemes(e.g.,[æ]cannotbefollowedby[s]andcannotbeprecededby[f];

thereverseconstraintistruefor[ɪ]).Participantsrequiredtwoexperimentalsessionson

separatedaystoacquirethesecond-orderconstraints(seealsoWarker&Dell,2006).

Whentheyreturnedtotheexperimentafteraweek,theyretainedtheirknowledgeofthe

experimentalconstraints,despitethehugeamountofconflictingevidenceparticipants

receivedfromEnglishintheinterveningweekbetweenexperimentalsessions(e.g.,that

3Whilephonotacticsclearlyvariesacrossdialects,theextentofthisvariationisunclear.StaumCasasanto(2008)providesevidencethatlisteners’processingofphonotacticvariantsisaffectedbyspeakerdialect,suggestingthatphonotacticscanvaryacrossdialects.Quantifyingthisvariationandexaminingitsimplicationsforphonotacticadaptationisakeyareaforfuturework.

33

[æ]canbefollowedby[s]inwordslikepass).Thissuggestslistenersmaytreatartificial

languagesasnon-nativelanguages,evenwhentheexposuretalkerhasanativelanguage

background.Asawhole,theseresultsareconsistentwiththehypothesisthatlearnerstreat

whattheylearninthelabasadistinctlanguage.

InExperiments1AandB,wetestthepredictionthatlistenerswillshowmore

robustadaptationwhentwotalkersdifferintheirlanguagebackgrounds,butnotwhen

theysharealanguagebackground.Notethatthisdistinctionispredictedonlyiflisteners

candetectthatthetwotalkersdifferinthelanguagebackgroundinthefirstplace.Assuch,

wepredictthatthedegreeofadaptationwillbeafunctionofhowmuchevidencelisteners

havethatthetwotalkersdifferinlanguagebackground.Weexaminethisbymanipulating

thestrengthofthecuetolanguagebackground.InExperiment2,weusephonotactic

adaptationtoexplorethestructureoflisteners’modelsofnon-nativephonotactics.Do

listenersmaintainmodelsofonlyanativevs.non-nativegrammar,ordotheymake

distinctionsbetweennon-nativelanguages?

2.3. Experiment1A

Inanartificiallanguageparadigm,weexposeparticipantstosecond-order

constraintsthatrequiretrackingtalkerinformation(e.g.,TalkerA’scodasarerestrictedto

[s,ʃ,f];TalkerB’scodasarerestrictedto[p,t,k]),whilemanipulatingthelanguage

backgroundofthetwotalkers.Theexperimentcontainsfourconditions:intheNative

Sharedcondition,bothtalkersarenativeEnglishspeakers;intheNon-NativeShared

34

condition,bothtalkersareFrenchspeakers;intheWeakDifferentandStrongDifferent

conditions,onetalkerisaFrenchspeaker,whiletheotherisanativeEnglishspeaker.Each

participantisexposedtoasinglepairoftalkersinabetween-participantdesign.TheWeak

DifferentandStrongDifferentconditionsaredistinguishedbythestrengthoftheacoustic

cuetotheFrenchtalker’slanguagebackground:intheStrongcondition,theFrenchtalker

producesavoweluncharacteristicofEnglish(frontrounded[y]);intheWeakcondition,

theFrenchspeakerproducesthemoreEnglish-likebackrounded[u]vowel(seeAppendix

AforacousticanalysisofFrenchvowels).Notethatboththefrontrounded[y]andback

rounded[u]Frenchvowelsareperceptuallyassimilatedto[u]bynativeEnglishlisteners

(Levy,2009);thatsaid,inboththeWeakandStrongconditions,thereareanumberofcues

totalkerlanguagebackground,astherearemanyphoneticdifferencesbetweenFrenchand

Englishbeyond[y].First,whileFrenchandEnglish[i]areacousticallysimilar(Strange,

Weber,Levy,Shafiro,Hisago,andNishi,2007),French[u]isproducedwithalowerF2(i.e.,

furtherback)thanEnglish[u],althoughthisdifferenceislikelynotaslargeasthatbetween

French[y]andEnglish[u](Flege,1987).Second,voicingdistinctionsforFrenchplosives

differfromthoseinEnglish:Frenchvoicelessplosivesareshort-lagandunaspirated(i.e.,

shortvoiceonsettime),ratherthanlong-lag(longvoiceonsettime)andaspirated,asin

English;andFrenchvoicedplosivesarefrequentlypre-voiced(negativevoiceonsettime)

ratherthanshort-lag,asinEnglish(Caramazza&Yeni-Komshian,1974).Third,coronal

consonants—particularlyplosivessuchas[t]—tendtobeproducedfurtherforwardinthe

mouth(i.e.,asdentalstops)inFrenchthaninEnglish(Dart,1998).

35

Table2.1.SummaryofconditionsinExperiment1A,alongwithexperimentalspeakerlanguagebackground,gender,andstimulusvowels.NotethatvirtuallyalllistenerswerenativeEnglishspeakers.

NativeShared Non-NativeShared

WeakDifferent

StrongDifferent

SpeakerLanguageBackground

SharedEnglish

SharedFrench

Englishvs.French

Englishvs.French

Englishvs.FrenchVowels

[i,u][i,u]

[i,y][i,y]

[i,u][i,u]

[i,u][i,{u/y}*]

SpeakerGender Different Different Same SamePredictedDegreeofAdaptation

Low Low Moderate High

*N.B.ForStrongDifferentcondition,Frenchsyllablesincluded[y]infamiliarizationsyllablesand[u]ingeneralizationsyllables.

Iflistenersadaptbasedontheirpriorexperiencewithphonotacticvariationand

talkerlanguagebackground,theyshouldadapttoagreaterdegreeintheDifferent

conditions,sincetalkerswhodifferinlanguagebackgroundaremorelikelytodifferin

theirphonotacticgrammars.AmongtheDifferentconditions,thetwotalkersare

phoneticallylessdistinctintheWeakcondition;assuch,listenershavelessevidencethat

thetwospeakersdonotsharealanguagebackground.Thuswepredictagreaterdegreeof

adaptationfortheStrongDifferentconditionthantheWeakDifferentcondition.Inboth

Sharedconditions,talkersdonotdifferinlanguagebackground;listeners’priorexperience

shouldsuggestthatthetalkerswillunlikelydifferintheirphonotacticgrammars.Assuch,

wepredictthesmallestdegreeofadaptationintheseconditions.

Participantsaretestedusingacontinuousrecognitionmemorytask(Bernard,2015,

2017;Denby,etal.,2017;Steele,etal.,2015),inwhichtheyareauditorilypresentedwitha

seriesofsyllablesandaskedwhethertheyhavepreviouslyheardeachsyllablewithinthe

36

experiment.Participantsarefirstexposedtomultiplerepetitionsofasetoffamiliarization

syllables,allofwhichfollowthephonotacticconstraint(e.g.,SpeakerAsaysfut;SpeakerB

sayspuf).Afterthefirst4repetitionstothefamiliarizationsyllables,listenershear9more

repetitionsoftheentiresetoffamiliarizationsyllables,butnowwithahandfulofnovel

generalizationsyllablesmixedin.Halfofthesearelegal(i.e.,followthephonotactic

constraint),whiletheotherhalfareillegal(i.e.violatetheconstraint;forexample,Speaker

Asayingtish;SpeakerBsayingtuk).Iflistenersaretrackingtheconstraint,generalization

syllablesthatfollowtheconstraintshouldseemmorefamiliarthanthosethatdonot;as

such,participantsshouldbemorelikelytoincorrectlybelievetheyhadpreviouslyheard

legalgeneralizationsyllables.Forexample,aparticipantmighthearSpeakerAsayfut,kit,

sik,tup,etc.,multipletimesduringfamiliarization.Ifthatparticipantistrackingthe

constraint,duringgeneralizationtheymaybelievetheyhadpreviouslyheardtut,since

syllableswithsimilarphonotacticpatterns(i.e.,voicelessstopsincodaposition)appeared

infamiliarization.Incontrast,participantsshouldbeunlikelytofalsealarm(i.e.,incorrectly

respond“yes”)totus,however,sincenosyllablesspokenbyTalkerAinfamiliarization

containedcodafricatives.

Notethatspeakergenderwasalsomanipulatedacrossconditions:intheShared

conditions,speakersdifferedingender,whileintheDifferentcondition,speakersshareda

gender.Muchlikeaccent,genderconveyssociolinguisticdifferencesbetweenspeakers

(e.g.,Oh,2011).Thisservedasacontrolonphoneticandsocialdistancebetweentalkersin

eachcondition:whiletalkersintheDifferentconditionsweredistinguishedbytheiraccent,

talkersintheSharedconditionsweredistinguishedbytheirgender.Assuchineach

37

conditionthetwotalkersdifferedalongsocialandphoneticlines,eitherbygenderor

accent.

Aninitialpilotstudy(seeAppendixB)wasruntoapproximatethenumberof

participantsneededforrequisitestatisticalpower(seeAppendixCfordetailsofpower

analysis).Thedesignandanalysisoftheexperiment—includingpredictions,numberof

participants,stimulusdesign,andmodelstructure—weredefinedbeforedatacollectionin

apre-registrationontheOpenScienceFoundationplatform(osf.io/dbcqx/).

2.3.1. Participants

Basedonapoweranalysis(seeAppendixCfordetails),256participants,split

evenlybetweenthe4conditions(64percondition),wererequired.However,participants

hadtopassasetofexperimentalcriteria(seeDataAnalysissection)toensurethatthey

wereadequatelyattendingtothetask.Assuch,participantswereiterativelyrecruiteduntil

therewere64participantswhopassedthecriteriaineachcondition.Atotalof455

participantswererecruitedthroughAmazonMechanicalTurk(AMT;Buhrmester,Kwang,

andGosling,2011);ofthese,260(57.1%)passedthecriteria.Thispassingratewassimilar

topreviousstudiesusingthisparadigmoverAMT(seeSteeleetal.,2015andDenbyetal.,

2018;seeAppendixDforfullbreakdownofparticipantpassingrates).Duetolimitations

withinouronlineframeworkandAMT,4participantswhopassedthecriteriawere

exposedtoauniqueexperimentallistthatapreviousparticipanthadbeenexposedto.

Threeoftheseparticipantswereexcluded;onesuchparticipantwasincluded,however,in

38

theWeakDifferentcondition,asoneuniqueexperimentallistdidnothaveaparticipantdue

toexperimentererror.ParticipantswererequiredtohaveU.S.IPaddresses,andwere

fluentspeakersofEnglish;98.4%ofparticipantswhopassedthecriteriaself-identifiedas

nativespeakersofEnglish,while2participantsself-identifiedasspeakinganon-North

AmericandialectofEnglish.99.2%ofparticipantswhopassedthecriteriahadnospeechor

hearingimpairments.(Notethatmodelresultswerequalitativelyidenticalwhennon-

nativeandhearing-andspeech-impairedparticipantswereexcludedfromtheanalysis.)

2.3.2. Stimuli

Stimuliwererecordedinasoundproofboothata44.1kHzsamplingrate,and

normalizedto60dBSPL.4talkersrecordedstimuli:afemalenativeEnglishspeaker;a

malenativeEnglishspeaker;afemalenativeFrenchspeaker;andamalenativeFrench

speaker.Talkersproducedsyllablesfromorthographicrepresentationsofsyllablesona

monitor;orthographyreflectedthelanguagebackgroundofthespeaker.BothFrench

talkersweremultilingual,butwereinstructedtoproducethesyllablesasthoughtheywere

French,ratherthanEnglish,words.Syllableswerepresentedinarandomorder.

Stimuliconsistedofconsonant-vowel-consonantsyllableswithvoicelessstops[p,t,

k]andvoicelessfricatives[f,s,ʃ]asonsets.VowelsfortheEnglishspeakerareeither[i]or

[u].FortheFrenchspeakers,vowelsare[i]and[u]intheWeakDifferentcondition;inthe

StrongDifferentcondition,vowelsinfamiliarizationsyllableswere[i]and[y];for

39

generalizationsyllablesvowelswere[i]and[u].Theresultwasatotalof108possible

syllables(6onsetconsonants*3vowels*6codaconsonants)recordedbyFrench

speakers,and72possiblesyllables(6onsets*2vowels*6codas)recordedbyEnglish

speakers(asEnglishspeakersonlyproduced[u]andnot[y]).Participantswereexposedto

72uniquesyllablesineachcondition.

2.3.3. Procedure

Participantswereaskedtofilloutademographicformthatincludedinformation

abouttheirlanguagebackground,geographicareasinwhichtheyhadpreviouslyresided,

whethertheywereanativeornon-nativespeakerofEnglish,andwhethertheyhadany

hearingorlanguageimpairments.Participantswerefreetooptoutofansweringany

questions.

Toensurelistenershadaworkingaudioset-upandbasicfluencywithEnglish,an

audiopre-testwasadministeredinwhichlistenersidentified2Englishwordsspokenbya

talkernotinvolvedintherestoftheexperimentbytypingthewordswiththeirkeyboards.

Participantsperformedarecognitionmemorytask.Thequestion“Haveyouheard

thisbefore?”wasonthescreenfortheentireexperiment.Oneachtrial,anauditory

stimuluswaspresented.Participantsansweredthequestionbyclickinga“Yes”or“No”

buttononthescreen.Aftereachclick,therewasa500msinterstimulusintervalbeforethe

followingstimulusplayed.The“Yes”and“No”buttonsdisappearedfromthescreenuntil

thestimuluscompletedplaying.Participantshadunlimitedtimetoanswerthequestion,

40

andnofeedbackwasprovided.Therewerenobreaksinbetweenexperimentalblocks;

blockswerenotdemarcatedinanywaytotheparticipant.

2.3.4. Design

Stimuliweresplitinhalf,intogeneralizationandfamiliarizationsyllables(36each),

byonset-vowelpairs,andcounter-balancedacrossparticipants.Forexample,ParticipantA

hearstheonset-vowelpair[tu_]infamiliarizationsyllables(e.g.,toof)andtheonset-vowel

pair[ti_]innovelgeneralizationsyllables(e.g.,teef);theconversepatternholdsfor

ParticipantB(e.g.,[ti_]infamiliarization;[tu_]ingeneralization).Onset-vowelpairswere

[ti],[hi],[su],[pi],[ku],[fu]foronepattern,and[tu],[hu],[si],[pu],[ki],[fi]fortheother.

Amongthe36familiarizationsyllables,half(18)willendinfricatives,whilehalfwillendin

stops.Thesesubsetsof18syllableswilleachberepeatedbyadifferenttalker,suchthata

giventalkerwillonlyrepeatsyllablesendingineitherfricativesorstops.Thus,during

familiarizationparticipantswillbeexposedtoaphonotacticconstraintlinkingmannerin

codaposition(fricativevs.stopcoda)andspeaker.Whichtalkerproduceswhichsetis

counterbalancedacrossparticipants.Amongthe36generalizationsyllables,eachspeaker

produceshalf(18)oftheset.Amongthissubset,half(9)followtheconstraintestablished

inthefamiliarizationset,andhalfviolatethisconstraint(i.e.,bothspeakerssaynovel

generalizationsyllablesthatendinbothstopsandfricatives).

Thefirst4blocksoftheexperimentconsistsofthefamiliarizationphase.Ineach

block,participantsareexposedtothe36familiarizationsyllables(halfsaidbyeach

41

speaker)inrandomorder.Inthegeneralizationphase,thereare9furtherrandomly

orderedrepetitionsofthefamiliarizationset,buteachrepetitionisnowintermixedwith4

generalizationsyllables.Thisresultsinatotalof504trials(36familiarizationsyllables*13

blocks+36generalizationsyllables).

InbothoftheSharedconditions,thetwotalkershavedifferentgenders(e.g.,Male

EnglishandFemaleEnglishtalkerinNativeShared).IntheDifferentconditions,however,

talkershavethesamegender;talkergenderwascounter-balancedacrossparticipant(e.g.,

ParticipantAhearsafemaleFrenchtalkerandafemaleEnglishtalker;ParticipantBhears

amaleFrenchtalkerandamaleEnglishtalker).

2.3.5. DataAnalysis

Followingpreviouswork(Denbyetal.,2017;Steeleetal.,2015),participantshadto

passasetofcriteriatoensurethattheywereadequatelyattendingtothetask:asin

previousstudies,duringthegeneralizationphase(blocks5-13),participantsmustcorrectly

acceptatleast90%ofthesyllablestheyhadpreviouslyheard,andcorrectlyrejectatleast

10%ofthenovelgeneralizationsyllablesthattheyhadnotheard(notethatlooseningthe

criteriatoincludeagreaternumberofparticipantsdoesnotqualitativelyaltertheresults;

seeAppendixD).Participantswhodidnotpassthesecriteriawereexcludedfromthe

42

analysis.Inaddition,forparticipantswhoattemptedtocompletetheexperimentmultiple

timeswithinasinglesession,onlythefirstattemptwasincluded.4

Generalizationdatawasanalyzedusinglogisticmixed-effectsregressionswith

maximaleffectsstructures(Barr,Levy,Scheepers,andTily,2013).Thedependentmeasure

wastherateatwhichparticipantsfalsealarmed(e.g.,incorrectlyresponded“yes”tonovel

syllables).Fixedeffectsforthemodelconsistedoflegalityandthreecontrast-codedterms:

languagedifference,inwhichtheSharedandDifferentconditionswerecontrasted;

strength,inwhichtheWeakandStrongDifferentconditionsarecontrasted;andaccent,in

whichthetwoSharedconditionsarecontrasted.Inaddition,aninteractiontermwas

includedbetweenlegalityandeachofthecontrast-codedterms.Randomeffectsincluded

randominterceptsandrandomslopesbylegalityforbothparticipantsanditems.5Finally,a

likelihoodratiotest,betweenmodelswithandwithouteachcontrasttermasafixedeffect,

wasincludedtotestforstatisticalsignificance.

Wemeasurethedegreeofadaptationusingthesizeofthelegalityadvantage:the

“yes”responseratestolegalgeneralizationsyllablesminusthe“yes”responserateto

illegalsyllables.Ouraccountpredictsthatlistenersadaptwhentheirpriorexperience

suggeststhatthetwotalkersarelikelytohavedifferentphonotacticgrammars.Thisshould4Therewereanumberofreasonswhyparticipantswouldattempttheexperimentmultipletimes(e.g.,iftheyaccidentallyclosedtheirbrowserwindowhalfwaythrough).5Notethatrandominterceptsandrandomslopesforparticipantsanditemsbylegalitywasthemaximaleffectsstructure.Itemsweredefinedasindividualtokensspokenbyspecifictalkers(e.g.,Frenchmaletalker’s[tif]),ratherthanmoreabstract“phonological”syllables(e.g.,/tif/spokenbyalltalkers).Assuch,participantsindifferentconditionswereexposedtoadifferentsubsetofsyllables,andcontrasttermscouldnotbeincludedasrandomslopesforitems.

43

yieldaninteractionbetweenlegalityandthelanguagedifferenceterms,suchthatthe

legalityadvantageislargerintheDifferentconditions(i.e.,whentalkersdifferintheir

languagebackgrounds)thanintheSharedconditions.Further,asadaptationrequiresthat

listenersrecognizethetalkersashavingdifferentlanguagebackgrounds,wepredictthe

legalityadvantagewillbelargerwhenthecuetolanguagebackgroundisstronger(i.e.,

morerobustadaptationintheStrongDifferentconditionthantheWeakDifferent

condition),asshownbyaninteractionbetweenlegalityandcue.Finally,listenerbehavior

shouldnotchangebetweenthetwoSharedconditionsdependingonwhetherthetalkers

arenativeornon-nativespeakers.InbothSharedconditions(i.e.,twoFrenchtalkersortwo

Englishtalkers)thetalkerssharealanguagebackground,andlistenersshouldtherefore

infertheyshareaphonotacticgrammar.Assuch,wepredictnointeractionbetweenthe

legalityandaccentcontrastterm.

2.3.6. Results

A95%confidenceinterval(CI)foreachanalysisofmeanvalueswasestimatedusing

abootstrapmethod,inwhichthedistributionofastatisticisestimatedbyrepeatedly

resamplingfromtheobserveddata(withreplacement).Distributionsformeansacross

participantswereestimatedwith1,000replicates,samplingacrossmeanswithineach

participant.

Participantscorrectlyacceptedameanof91.0%offamiliarizationsyllables(CI

[90.6%,91.3%]);participantsfalselyrecognized(i.e.,incorrectlyresponded“yes”to)

44

55.9%ofnovelgeneralizationsyllables(CI[53.2%,58.6%]).Thecrucialmeasure,however,

wasthedifferenceintherateoffalserecognitionsforlegalvs.illegalsyllables,andwhether

this“legalityadvantage”wasmodulatedbytalkerlanguagebackground.Themeanlegality

advantageacrossparticipantswas12.5%(CI[10.5%,14.7%]),replicatingpreviousresults

showingthatlistenersshowhigherfalserecognitionratesonnovellegalsyllables(i.e.,

syllablesfollowingconstraintsthey’vebeenpreviouslyexposedto)thannovelillegal

syllables.Moreover,thelegalityadvantageismodulatedbylanguagebackground—ascan

beseeninFigure2.1,thelegalityadvantageismodestintheNativeSharedcondition,and

relativelylargeintheotherthreeconditions.

Figure2.1.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment1A.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment1A.Inbothpanels,errorbarsreflectbootstrapped95%confidenceintervals.

45

Ouranalysisshowedasignificantmaineffectoflegality(β=0.64,s.e.β=0.06,χ2(1)

=73.6,p<.0001),aslistenersweremorelikelytofalselyrecognizelegalsyllablesover

illegalsyllables.Inaddition,therewasasignificantinteractionoflegalitywiththelanguage

differencecontrastterm(β=0.72,s.e.β=0.20,χ2(1)=12.6,p<.001),aslistenersshowed

agreaterlegalityadvantageintheDifferentconditionsthanintheSharedconditions.

Legalityalsointeractedwithaccent(β=0.45,s.e.β=0.14,χ2(1)=9.8,p<0.01),butnot

strength(β=-0.05,s.e.β=0.14,χ2(1)=0.14,p=.70).Inotherwords,thelegality

advantagewasgreaterintheNon-NativeSharedconditionthantheNativeShared

condition,butwasnotdifferentacrosstheStrongandWeakDifferentconditions.(Seefull

modelresultsinAppendixE.)

2.3.7. Experiment1ADiscussion

Experiment1Aexposedlistenerstotalker-specificphonotacticconstraintswhile

modulatingthelanguagebackgroundoftalkers.Listenerswereabletosuccessfullyadapt

withineachcondition,acquiringtalker-specificconstraints.Moreover,thisadaptationwas

modulatedbythelanguagebackgroundofthetalkers:listenersshowedmodestdegreeof

adaptationwhenexposedtotwotalkerswithasharednativelanguagebackground(Native

Sharedcondition),andagreaterdegreeofadaptationifeitherorbothtalkershadanon-

nativelanguagebackground(StrongDifferent,WeakDifferent,andNon-NativeShared).

Therewasnodifferenceinadaptationbasedonthestrengthofthecuetolanguage

46

background(StrongDifferentvs.WeakDifferent),suggestingthatevenwiththeweakercue

tothenon-nativelanguagebackgroundoftalkers(i.e.,theFrench[u]vowel,ratherthan

[y]),listenersareconfidentofthenon-nativelanguagebackgroundofthetalker.

Countertoourpredictions,however,adaptationwasaffectedbylanguage

backgroundevenwhenbothtalkerssharedalanguage:therewasagreaterdegreeof

adaptationwhenbothtalkerssharedanon-nativelanguagebackgroundthanwhenthey

sharedanativelanguagebackground.Perhapsmoresurprising,adaptationwasequally

robustwhentalkerssharedanon-nativelanguagebackgroundaswhentheirlanguage

backgroundsdiffered(i.e.,onenativeandonenon-nativetalker).Itispossiblethatany

inclusionoftalkerswithanon-nativelanguagebackgroundincreaseslistenerconfidence

thattalkersarespeakingtwodifferentlanguages.Thismaybebecauseoftheasymmetryin

listenerknowledgeoftheirnativephoneticsvs.non-nativephonetics:duetolisteners’

extensiveknowledgeoftheirnativelanguage,whentheyencountertwonativespeakers

theyarelikelyconfidentthatthosetwospeakerssharealanguage(evenwhentheyare

bothspeakinganartificial,non-nativelanguage).Whenlistenersencountertwotalkers

withasharednon-nativelanguagebackground,ontheotherhand,theymaybeless

confidentthatthesetalkerssharealanguagebackground,giventheirrelativepaucityof

experiencewithnon-native(inthiscase,French)phonetics.

Iftheasymmetryinlistenerknowledgebetweennativeandnon-nativephoneticsis

drivingthedifferencebetweenthetwoSharedconditions,however,thisasymmetryshould

alsoresultinthegreatestdegreeofadaptationfortheDifferentconditions,whichwasnot

47

thecase.Thatis,listenerconfidenceofhavingencounteredmultiplelanguagesshouldbe

highestwhenoneofthoselanguagesisanativelanguage.

ThereweretwolimitationsofExperiment1Athatmayhaveaffectedadaptation.

First,theproductionsofthetwoFrenchtalkersshowedmarkedlydifferentpitchcontours,

tothepointthatlistenersmayhaveinferredthatthetwotalkersdidnotsharealanguage

background,increasingthelegalityadvantageintheNon-NativeSharedcondition.Thismay

havebeenduetodifferencesduringrecording,orthedifferentbackgroundsofthetwo

talkers.ThemaleFrenchspeakerwas23yearsold,andhadlivedintheUnitedStatesfor

lessthanayear.HewasfromParis,andself-identifiedasspeakingastandarddialectof

French.ThefemaleFrenchspeakerwas41yearsold,hadlivedintheUnitedStatesfor13

years,wasfromsouthofFrance,andidentifiedasspeakinganon-standarddialectof

French.

Toaddressthislimitation,inafollow-upexperimentreplicating3ofthe4

conditionsinExperiment1A(seebelow),werecordedanovelfemaleFrenchspeaker,

whoselanguagebackgroundwasmoresimilartothatofthemaleFrenchspeaker,andwho

wasinstructedtoimitatethemalespeaker’sproductionstoensurephoneticsimilarity

acrossspeakers.Assuch,wepredictalowerdegreeofadaptationintheNon-NativeShared

conditioninExperiment1Bthanin1A.

AsecondlimitationofExperiment1AwasthatintheStrongDifferentcondition,

listenerswereexposedtofamiliarizationsyllablesthatincludedtheuncharacteristic

French[y]vowel;generalizationsyllables,however,hadtheFrench[u]vowel.Thismeant

thegeneralizationsetswereidenticalacrossStrongandWeakconditions,allowingfora

48

moredirectcomparison.However,itmayhavealsoattenuatedadaptationintheStrong

Differentcondition,giventhat[u]isaweakercuetotalkerlanguagebackground.Moreover,

itincreasedthephoneticdistancebetweenfamiliarizationandgeneralizationsets,as

listenersencounteredanovelFrenchvowelinthegeneralizationsetthatwasnotpresent

infamiliarizationsyllables.LowfalserecognitionratesforsyllablesintheStrongDifferent

conditionspokenbyaFrenchtalkerandcontaining[u](38.1%)reflectedthis.Thisislower

thanfalserecognitionforFrenchsyllablescontaining[i](63.7%)intheStrongDifferent

condition,aswellasFrenchsyllablescontaining[u]intheWeakDifferentcondition

(60.0%).

Toaddressthislimitation,intheStrongDifferentconditionofExperiment1B,

familiarizationandgeneralizationsyllablesspokenbyFrenchtalkerscontainedmatching

vowels.IftheincreasedphoneticdistanceintheStrongDifferentconditiondepressedthe

legalityeffectforthatcondition,wewouldpredictagreaterdegreeofadaptationforthe

StrongDifferentconditioninExperiment1Bthanin1A.

2.4. Experiment1B

InExperiment1A,participantsadaptedtoanunexpectedlyhighdegreeintheNon-

NativeSharedconditionrelativetotheDifferentconditions.InExperiment1B,threeofthe

conditionsfromExperiment1Awerereplicated(StrongDifferent,WeakDifferent,andNon-

NativeShared)whiletwolimitationsofthepreviousexperimentwereaddressedthatmay

havecausetheunexpectedresults.

49

2.4.1. Participants

AsinExperiment1A,participantswereiterativelyrecruitedfromAMTuntilthere

were64participantsineachofthethreeconditionswhopassedtheexperimentalinclusion

criteria.Atotalof418participantswererecruited,ofwhich192(46.4%)passedthe

criteria.Noparticipantswereexcludedduetoexposuretopreviouslyseenexperimental

lists.98.9%ofparticipantswhopassedthecriteriaidentifiedasnativeEnglishspeakers.All

participantsidentifiedashavingnospeechorhearingimpairments.Noparticipant

identifiedasspeakinganon-AmericandialectofEnglish.(Notethatmodelresultswere

qualitativelysimilarwhennon-nativeparticipantswereexcludedfromtheanalysis.)

2.4.2. Stimuli

Stimulifrom3ofthe4talkerswereidenticaltothatinExperiment1A;however,

stimulifromanovelfemaleFrenchspeakerwererecordedtoreplacethestimuliofthe

femaleFrenchspeakerfromExperiment1A.Inasoundproofbooth,thenovelfemale

FrenchspeakerheardeachofthemaleFrenchspeaker’sproductionsinrandomorderover

headphones.Afterthemalespeaker’sproductionwasplayed,shewasinstructedtoimitate

it;eachsyllablewasalsoprovidedinFrenchorthography,andappearedonamonitorafter

theaudiohadfinishedplaying.

ThenovelfemaleFrenchspeakerwas24yearsold,grewupinthesouthwest

ofFrance,livedinParisasanadult,andhadlivedintheUnitedStatesforlessthanayearat

50

thetimeofrecording.Sheself-identifiedasspeakingastandarddialectofFrenchasan

adult,despitehavinggrownupspeakinganon-standarddialect(SouthwesternFrench).

IntheStrongDifferentconditioninExperiment1B,vowelsspokenbyFrench

speakersinbothfamiliarizationandgeneralizationsyllableswerealways[i]or[y].(This

differedfromtheStrongDifferentconditioninExperiment1A,inwhichFrenchspeakers

used[i]and[y]infamiliarizationsyllables,but[i]and[u]ingeneralizationsyllables.)

StimuliwereotherwiseidenticaltothoseinExperiment1A.

2.4.3. DataAnalysis

Significancewasassessedusingalogisticmixed-effectsregressionidenticaltothat

inExperiment1A,withtheexceptionofafixedeffectforaccent,whichwasnotincluded

(therewasnoNativeSharedconditioninExperiment1B).Themodelhadfixedeffectsof

legality,languagedifference(i.e.,Non-NativeSharedvs.bothDifferentconditions)and

strength(i.e.,Weakvs.StrongDifferentconditions).Aninteractiontermwasincluded

betweenlegalityandbothcontrast-codedterms;randomeffectsincludedrandom

interceptsandrandomslopesbylegalityforbothparticipantsanditems.

WepredictasignificantdifferencebetweentheDifferentconditionsandtheNon-

NativeSharedcondition,asshownbyaninteractionbetweenlegalityandthelanguage

differenceterms.Wealsopredictasignificantinteractionbetweenlegalityandthestrength

contrastterm.

51

2.4.4. Results

Participantscorrectlyacceptedameanof90.3%offamiliarizationsyllables(CI

[89.7%,90.9%]);participantsfalselyrecognized(i.e.,incorrectlyresponded“yes”to)

60.2%ofnovelgeneralizationsyllables(CI[57.3%,63.1%]).Themeanlegalityadvantage

acrossparticipantswas19.4%(CI[17.1%,21.8%]).Critically,thelegalityadvantageis

modulatedbylanguagebackground—ascanbeseeninFigure2.2,thelegalityadvantageis

moderateintheNon-NativeSharedcondition,andlargeintheDifferentconditions(the

NativeSharedconditionfromExperiment1Awasincludedforreference).

Figure2.2.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment1B.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment1B.Inbothpanels,errorbarsreflectbootstrapped95%confidenceintervals.

Alogisticmixedeffectsregressionfoundasignificantmaineffectoflegality(β=

1.02,s.e.β=0.07,χ2(1)=127.6,p<.0001),aswellaslanguagedifference(β=-1.06,s.e.β=

52

0.19,χ2(1)=28.82,p<.0001),aslistenersweremorelikelytofalselyrecognizelegal

syllables,aswellassyllablesintheDifferentconditions.Inaddition,therewasasignificant

interactionoflegalitywiththelanguagedifferencecontrastterm(β=0.57,s.e.β=0.18,χ2

(1)=9.81,p<.01),aslistenersshowedagreaterlegalityadvantageintheDifferent

conditionsthanintheSharedcondition.Legalitydidnotinteractwithstrength(β=-0.02,

s.e.β=0.15,χ2(1)=0.03,p=.87),asthelegalityadvantagewasnotsignificantlydifferent

acrosstheStrongandWeakDifferentconditions.

2.4.5. Discussion

Experiment1Breplicatedtheadaptationtotalker-specificphonotacticconstraints

foundinExperiment1A,withlistenersadaptingineachcondition.Moreover,listeners

adaptedtoagreaterdegreewhentalkersdifferedintheirlanguagebackground(Different

conditions)thanwhentheysharedanon-nativelanguagebackground(SharedNon-Native

condition),unlikeinExperiment1A.Thisprovidesevidencethatthedifferenceinlanguage

backgroundbetweentalkersiscritical,asopposedtothesimplepresenceofnon-native

talkers.

WefurtherpredictedthatthechangesinstimulusdesigntoExperiment1Bwould

resultin(a)anincreaseinthelegalityadvantageforStrongDifferentconditiondueto

consistentvowelsacrossgeneralizationandfamiliarizationsyllables,and(b)adeclinein

thelegalityeffectfortheNon-NativeSharedconditionduetotheincreasedphonetic

similarityofthetwoFrenchtalkers.WhilethelegalityadvantagefortheStrongDifferent

53

conditiondidincreaseacrossExperiments1Aand1B(fromameanof15.7%to23.1%),a

similarincreasewasfoundintheWeakDifferentcondition(from16.1%to22.7%),

suggestingthechangeinthedesignoftheStrongDifferentconditionwasnotthecauseof

thisincrease.Inaddition,fortheNon-NativeSharedcondition,thelegalityeffectwas

roughlyequivalentacrossExperiments1Aand1B(ameanof13.6%in1Aand12.7%in

1B),countertoourprediction.

TheinclusionofanovelfemaleFrenchspeakerinExperiment1Bappearstoaccount

fortheincreasedlegalityadvantageintheDifferentconditions:listenerswhoheardtwo

malespeakersintheDifferentconditionsshowedasimilarlegalityadvantageacrossthe

twoexperiments(ameanof20.2%in1Aand19.3%in1B);listenerswhoheardtwofemale

speakers,however,showedasubstantiallyhigherlegalityadvantageinExperiment1B(a

meanof25.8%)thanin1A(11.6%;seeAppendixDfortalkermeansineachconditionand

experiment).

WhydidtheinclusionofthenovelfemaleFrenchspeakerincreaseadaptationin

bothDifferentconditions,withoutloweringadaptationintheNon-NativeSharedcondition?

OnepossibilityisthattheoriginalfemaleFrenchspeakerinExperiment1Awasnot

sufficientlyphoneticallydistinctfromthefemaleEnglishspeaker,perhapsduetothe

Frenchspeaker’sextendedtimeintheUnitedStates.Ifthiswerethecase,listenerswould

haveinferredthattheysharedalanguagebackground,resultingindecreasedratesof

adaptation.Notethatthisdifferedfromouroriginalprediction:thatthefemaleFrench

speakerinExperiment1AwasnotsimilarenoughtothemaleFrenchspeaker,resultingin

higherthanexpectedadaptationintheNon-NativeSharedcondition(wesawsimilar

54

adaptationforthisconditioninExperiments1B).Asecondpossibilityisthatthefemale

Frenchspeaker’sanomalouspitchcontoursweredistracting,shiftinglistenerattention

awayfromthesegmentalleveldifferencesbetweenspeakers,andtowardstheprosodic

differences.

TheincreaseofadaptationintheDifferentconditions,whateverthecause,suggests

thatthelow-levelphoneticpropertiesoftalkers,andthedifferencesorsimilarities

betweentalkers,affectlistenerinferencesabouttalkerlanguagebackground.Replicating

thisexperimentwithnoveltalkerpairsandlanguagesisnecessarytoensurethatthe

patternofadaptationfoundinExperiment1was,infact,spurredbydifferencesinlanguage

background,ratherthantheresultofarbitraryindividualvariation.

Finally,asinExperiment1A,therewasnodifferenceinadaptationbasedonthe

strengthofthecuetolanguagebackground,providingfurtherevidencethatthe“weak”cue

issufficientforlistenerstodetectthetalker’slanguagebackground.

2.4.6. Experiment1conclusion

Experiments1AandBprovideevidencethatlisteners’previousexperiencewith

phonotacticvariation—thatspeakerswithdifferentlanguagebackgroundsexhibitalarge

degreeofphonotacticvariation,whilespeakerswithinaspeechcommunitydonot—

constrainsadaptationtonovelphonotacticconstraints.Further,theresultssuggestthat

listenershaveastructuredmodelofphonotacticvariation,withnativeandnon-native

languageseachhavingseparatephonotacticgrammars.Thespecificityoflistener

55

knowledgeofnon-nativephonotactics,however,isunclear.InExperiment2,weinvestigate

whetherlistenersassigndifferentphonotacticgrammarstodifferentnon-nativelanguages

(aswellastheirnativelanguage).Alternatively,listenersmayonlyassignasingle

phonotacticgrammartotheirnativelanguage,6andasinglephonotacticgrammartoall

non-nativelanguages.

2.5. Experiment2

InExperiment2,usingasimilardesignandrecognitionmemoryparadigmtothatin

Experiments1AandB,weexposelistenerstotwotalkers,eachofwhomexhibitsa

differentnovelphonotacticpattern.Weconceptuallyreplicate2conditionsofExperiments

1AandBusingnovelstimuli,speakers,andlanguages(HindiandHungarian).IntheMixed

DifferentconditionlistenersareexposedtoonenativeEnglishspeaker,andonenon-native

speaker(eitherHindiorHungarian),broadlyreplicatingthedesignoftheDifferent

conditionsinExperiment1.IntheNon-nativeSharedcondition,listenersareexposedto

twonon-nativespeakerswhosharealanguagebackground(either2Hindispeakersor2

Hungarianspeakers).Toaddressthestructureoflistenerknowledge,weincludeanovel

condition:intheNon-nativeDifferentcondition,listenersareexposedtotwonon-native

speakerswhodifferintheirlanguagebackground(oneHindispeakerandoneHungarian

speaker).

6Inthecaseofmultilingualspeakers,onephonotacticgrammartoeachoftheirnativelanguages.

56

Table2.2.SummaryofconditionsinExperiment2,alongwithexperimentalspeakerlanguagebackground,gender,andstimulusvowels.NNstandsfornon-native.NotethatvirtuallyalllistenerswerenativeEnglishspeakers.

Non-NativeShared

MixedDifferent

Non-NativeDifferent

LanguageBackground

SharedHindiorHungarian

Englishvs.(HindiorHungarian)

Hindivs.Hungarian

Gender Different Different DifferentPredictedDegreeofAdaptation

Moderate High WithinNN:HighNativevs.NN:Moderate

Thewithinnon-nativedistinctionshypothesisandthenativevs.non-native

hypothesismakeidenticalpredictionsintheNon-nativeSharedcondition—moderate

adaptation,followingtheresultsofExperiment1—andtheMixedDifferentcondition—a

highdegreeofadaptation.Replicatingtheseresultswithnovelspeakersandlanguages

shouldprovidefurtherevidencethattalkerlanguagebackgroundaffectsadaptation.Inthe

Non-nativeDifferentcondition,however,thewithinnon-nativedistinctionshypothesis

predictsahighdegreeofadaptation,withlistenersinferringthatdifferentnon-native

languageshavedifferentphonotacticgrammars.Thenativevs.non-nativehypothesis,on

theotherhand,predictsasimilar,moderatedegreeofadaptationintheNon-native

DifferentandNon-nativeSharedconditions,asunderthishypothesislistenersdon’t

distinguishbetweendifferentnon-nativephonotacticgrammars.

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2.5.1. Participants

192participantswererequired(64participantsforeachofthe3conditions).To

reach192participantswhopassedtheexperimentcriteria(seebelow),441participants

wererecruited,202ofwhompassedthecriteria(45.8%).10participantswhopassedthe

criteriawereexposedtoanexperimentallistapreviousparticipanthadbeenexposedto

andassuchwereexcluded.AsinExperiment1,participantswererequiredtohaveaU.S.IP

address.98%ofparticipantsself-identifiedasnativespeakersofEnglish,while1

participantself-identifiedasspeakinganon-NorthAmericandialectofEnglish.98.4%of

participantself-identifiedashavingnospeechorlanguageimpairments.Allmodelresults

werequalitativelyidenticalwhennon-nativeandparticipantsandthosewithimpairments

wereexcluded.

2.5.2. Stimuli

Stimuliwererecordedinasoundproofboothata44.1kHzsamplingrateand

normalizedto60dBSPL.6talkersrecordedstimuli,with1maleand1femalespeakerfor3

languages:English,Hungarian,andHindi.Talkersproduceddisyllablesfromorthographic

representationsofdisyllablesonamonitor;orthographyreflectedthelanguage

backgroundofthespeaker(atransliteratedorthographywasusedforHindi).AllHindiand

Hungariantalkerswerebilingual,butwereinstructedtoproducestimuliasdisyllablesin

theirnativelanguage,ratherthanEnglish.Disyllableswerepresentedinarandomorder.

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Giventheaddeddifficultyofdetectingdifferencesintalkerlanguagebackground

betweentalkersoftwonon-nativelanguages,stimuliconsistedofdisyllablesratherthan

monosyllablestoprovidelistenerswithgreaterphoneticevidenceoftalkerlanguage

background.ThesyllablesmakingupthedisyllabicstimuliinExperiment2wereasubset

ofthoseusedinExperiment1.Consonantsconsistedofvoicelessstops[p,k]andvoiceless

fricatives[f,ʃ];[t]and[s],whichcanformcomplexonsetsinthesecondsyllable,werenot

usedtoensurethateachindividualsyllablewasparsedasconsonant-vowel-consonant.For

EnglishandHindispeakers,vowelsconsistedof[i]and[u];forHungarianspeakers,vowels

consistedof[i]and[y].Thisresultedinatotalof32monosyllables(4onsets*2vowels*4

codas).

64disyllabicstimuliwerecreatedbysplittingthe32monosyllablesinto4groupsof

8,counterbalancedforcodapattern(fricativevs.stop)andonset/rhymepattern(onset

[k,f]matchedwithrhymes[uf,ih,uk,ip]vs.onset[h,p]matchedwithrhymes[if,uh,ik,

up]).Thesegroupsof8arefurthersplitintwo,suchthateachgrouphasaneven

distributionofsegmentsineachposition.Eachsubgroupof4iscrossedtocreate32

disyllables(4syllables*4syllables*2positions).Amongtheresulting128disyllables,all

disyllableswithgeminationandreduplicationareremoved,andsubsetswerechosensuch

thatsyllablesappearedanequalnumberoftimesinbothpositionswithineachgroup,fora

totalof64disyllables.

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2.5.3. Procedure

TheprocedurewasidenticaltothatofExperiment1.

2.5.4. Design

Stimuliweresplitinhalf,intogeneralizationandfamiliarizationdisyllables(32

each),byonset-vowel/codapairings,andcounter-balancedacrossparticipants.For

example,indisyllablesthatincludesyllablesendingincodas[k,f],ParticipantAhearsthe

onset-vowelpair[fu_](e.g.,fookpeek)infamiliarizationdisyllables,andtheonset-vowel

pair[fi_]innovelgeneralizationdisyllables(e.g.,feekpook).ParticipantBhearsthe

conversepattern(e.g.,feekpookinfamiliarization;fookpeekingeneralization).Amongthe

32familiarizationdisyllables,syllablesinhalf(16)endinfricatives,whilesyllablesinthe

otherhalfendinstops.

Thesetsweresplitinhalfagainintosubsetsof8,suchthateachsyllableonly

appearsonceineachposition(e.g.,fifappearsonceasthefirstsyllableandonceasthe

secondsyllable).Todecreasetheoverallconfusabilityofthesets,participantsheareach

speakerproduceonlyonesubsetof8infamiliarization(althoughtwiceasoften;see

below),whiletheothermatchingsubsetiswithheld.AsinExperiment1,eachspeaker

repeatsfamiliarizationdisyllablesthatendinadifferentcodapattern(e.g.,SpeakerAends

theirsyllablesinstops;SpeakerBinfricatives);whichtalkerproduceswhichsetis

counterbalancedacrossparticipants.

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Amongthe32generalizationsyllables,eachspeakerproduceshalf(16)oftheset.

Amongthissubset,half(16)followtheconstraintestablishedinthefamiliarizationset,and

halfviolatethisconstraint(i.e.,bothspeakerssaynovelgeneralizationdisyllablesthatend

inbothstopsandfricatives).

Thefirst2blocksoftheexperimentconsistsofthefamiliarizationphase.Ineach

block,participantsareexposedto2repetitionsofeachofthe16familiarizationdisyllables

(halfsaidbyeachspeaker)inrandomorder,foratotalof32tokensperblock.Pilottesting

suggestedthatduetotheincreasedsimilarityoftokensinthisstudy,tworepetitionsof

eachdisyllableperblockwererequiredtoensureadequatelevelsofrecognition

performanceonthefamiliarizationtokens.Inthegeneralizationphase,theserandomized

setsof32tokensarerepeatedin8furtherblocks;eachgeneralizationblockalsoincludes4

intermixedgeneralizationdisyllables.Thisresultsinatotalof352trials(16familiarization

disyllables*2repetitions/block*10blocks+32generalizationsyllables).

Toensurethatlistenerscanclearlytelltalkersapart,thetwotalkershavedifferent

gendersineachcondition.

2.5.5. DataAnalysis

AsinExperiment1,participantshadtopassasetofcriteriatoensurethatthey

adequatelyattendedtothetask.ToachievesimilaroverallpassingtothoseinExperiment

1,giventheincreasedconfusabilityofthefamiliarizationsetinExperiment2,thecriteria

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forperformancewereslightlylowered:participantshadtocorrectlyacceptatleast85%of

familiaritems(asopposedto90%inExperiment1).AsinExperiment1,participantshad

tocorrectlyrejectatleast10%ofthenovelgeneralizationitemsthattheyhadnotheard.

Finally,athirdcriterionwasincluded:participantshadtocorrectlyrejectnovel

generalizationitemsatleastasoftenastheyrejectedfamiliarizationitems(e.g.,ifa

participantcorrectlyacceptedfamiliarizationitemsonly85%ofthetime,theparticipant

hadtocorrectlyrejectgeneralizationsyllablesatleast15%ofthetime).Thisensured

participantswhowereunabletosufficientlydifferentiatefamiliarandnovelitemswerenot

includedintheanalysis.

Generalizationdatawasanalyzedusingalogisticmixed-effectsregression.Fixed

effectsincludedlegalityandtwocontrast-codedterms:languagedifference,inwhichthe

Non-NativeSharedconditionwascontrastedwiththetwoDifferentconditions;andnon-

nativelanguagebackground,inwhichtheNon-nativeSharedandNon-nativeDifferent

conditionscontrastedwiththeMixedDifferentcondition.Furthermore,themodelincluded

aninteractiontermbetweenlegalityandeachofthecontrast-codedterms.Therandom

effectsstructureincludedrandominterceptsandrandomslopesoflegalitybyboth

participantsanditems.

Thewithinnon-nativehypothesispredictsasignificantdifferencebetweentheNon-

nativeSharedandthetwoDifferentconditions,asindicatedbytheinteractionterm

betweenlegalityandthenon-nativeterm;thenativevs.non-nativehypothesisdoesnot

predictsuchadifference.Suchadifferencewouldindicatethatlistenersshowedalarger

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legalityadvantageintheDifferentconditions,despiteoneoftheseconditionsincluding

speakersoftwodifferentnon-nativelanguages.

2.5.6. Results

Participantscorrectlyaccepted89.3%offamiliarizationdisyllables(CI[88.7%,

90.0%])andfalselyrecognized69.8%ofgeneralization.Themeanlegalityadvantagewas

14.0%(CI[11.3%,16.5%]).Crucially,asshowninFigure2.3,thedifferenceinlanguage

backgroundmodulatesthelegalityadvantage:similartoExperiment1B,thelegality

advantageismoderateintheNon-NativeSharedcondition,andlargeinbothDifferent

conditions.

Figure2.3.A:FalserecognitionratesforlegalandillegalgeneralizationsyllablesinExperiment2.B:Legalityadvantage(falserecognitionrateonlegalgeneralizationsyllablesminusfalserecognitionrateonillegalgeneralizationsyllables)forExperiment2.Inbothpanels,errorbarsreflectbootstrapped95%confidenceinterval.

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Theresultsfromthelogisticmixedeffectsregressionshowamaineffectoflegality(β=

0.76,s.e.β=0.08,χ2(1)=62.83,p<.0001),showingthatlistenersweremorelikelytofalse

alarmonlegaldisyllables.Theinteractionbetweenlegalityandlanguagedifferencewas

alsosignificant(β=0.71,s.e.β=0.21,χ2(1)=11.1,p<.001),aslistenersshowedagreater

legalityadvantageontheDifferentconditionsthanintheSharedcondition.Legalitydidnot

interactwiththenon-nativebackgroundterm(β=-0.04,s.e.β=0.21,χ2(1)=0.03,p=

0.87),aslistenersdidnotshowalargerlegalityadvantageinthetwoNon-nativeconditions

vs.theMixedcondition.

2.5.7. Discussion

ListenersinExperiment2adaptedtotalker-specificconstraintsineachcondition.

ThisreplicatesfindingsfromExperiments1AandBusingnoveltalkers,languages,and

stimulusdesign,providingfurtherevidencethatlistenerscanadapttotalker-specific

constraints.AsinExperiments1AandB,thedegreeofadaptationwasmodulatedbythe

languagebackgroundofthetalkers:listenersshowedahighdegreeofadaptationwhen

talkersdifferedinthelanguagebackground(MixedDifferentandNon-NativeDifferent

conditions),andalow-to-moderatedegreeofadaptationwhentalkerssharedalanguage

background(Non-NativeShared).

ListenersadaptedatasimilarrateinbothDifferentconditions,regardlessof

whethertheywereexposedtooneHindiandoneHungariantalker(Non-NativeDifferent)

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oroneEnglishandoneHindi/Hungariantalker(MixedDifferent).Thissuggeststhat

listenersmakedistinctionsbetweendifferentnon-nativephonotacticgrammars,andassign

differentphonotacticgrammarstodifferentnon-nativelanguages.Inotherwords,ifthe

phoneticsoftwolanguagesareperceptiblydifferent—regardlessofwhethertheyare

nativeornon-nativelanguages—listenerscaninferthatthoselanguageshaveseparate

phonotacticgrammars.

HowcanweunderstandthesimilarlevelsofadaptationintheNon-NativeDifferent

andMixedDifferentconditions?Theseresultsareconsistentwiththehypothesisthat

participantsaretreatinginputtheyreceiveinphonotacticlearningexperimentsasanon-

native“lablanguage”.Participantsareexposedtononsensewordsinsemantically

meaninglesscontexts,andlikelyinfersuchlanguagesarenotnative.Thespeedwithwhich

participantsadapttonovelphonotacticconstraints(withinonetotwosessions)also

suggeststheyarelearninganovelphonotacticgrammar,ratherthanadjustingonewith

whichtheyhavealifetimeofexperience.Thisisfurthersupportedbyevidencein

productionthatspeakersmaintainexperimentalconstraintsforatleastaweek,and

possiblylonger,despiteinterveningevidencetothecontraryoutsideoftheexperiment

(Warker,2013).Inpreviousperceptionexperiments,listenerslearnrapidlydespitebeing

exposedtoasinglenativetalker.Inotherwords,itislikelythatlearnerstreatanyspeaker

intheexperimentalcontextasbeing“non-native”,evenifthatspeakerhasphonetics

consistentwithEnglish.ThustheMixedDifferentconditionhastwo“non-native”languages,

despiteoneofthemhavingEnglishphonetics.Assuchwedon’texpectdifferencesbetween

theMixedDifferentandNon-nativeDifferentconditions,givenlistenersmayinfertheyboth

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havespeakersoftwodifferentnon-nativelanguages.Notethatthisiscompatiblewiththe

moderateadaptationfoundintheNon-nativeSharedconditioninExperiment1.Weargue

thatthisisduetotheasymmetryinknowledgeofnativevs.non-nativephonetics.Inother

words,listenersarelikelytoknowthattwonativespeakersofEnglishsharealanguage

background;theyarelesslikelytoknowthattwoFrenchspeakersdo.

WhileExperiment2replicatedtherelativelyhigherlegalityadvantageinDifferent

vs.SharedconditionsfoundinExperiment1,theoveralllegalityadvantagesarelowerin

Experiment2(e.g.,inExperiment1BthemeanlegalityadvantageintheDifferent

conditionsis22.5%;inExperiment2it’s17.5%).Totheextentthatthesedifferencesin

effectsizesbetweenexperimentsaremeaningful,itislikelyduetodifferencesinthe

designsofthetwoexperiments.InExperiment2,thestimulussetwasmuchmore

confusablethaninExperiment1.Thislikelycausedtherelativelyhighoverallfalse

recognitionrate(57.7%inExperiment1;69.8%inExperiment2).Thisalsomayhave

loweredthelegalityadvantage,asparticipantsmayhavebeguntohitaceilingonfalse

recognitionratesforlegalsyllables.

2.6. ListenerLanguageBackgroundAnalysis

ResultsfromExperiments1and2stronglysuggestthatpreviousexperiencewith

non-nativelanguages,andthephonotacticvariationthatdifferentlanguagesexhibit,

constrainlistener’sadaptationtonovelnon-nativephonotactics.Listenersinferthat

speakersofdifferentnon-nativelanguagesareunlikelytoshareaphonotacticgrammar,as

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opposedtospeakerssharinganon-nativelanguagebackground.Buthowmuchexperience

withnon-nativelanguagesisnecessarytomakesuchinferences?It’spossiblethatthe

thresholdisquitelow,withmonolingualspeakersabletomakesuchinferencesthrough

theirdailyexposuretonon-nativelanguages.Alternatively,multilingualspeakersmay

morereadilymaketheseinferencesbasedontheirpastexperiencelearninglanguages.

Participantsreportedtheirlanguagebackgroundsonaquestionnairebeforetaking

theexperiment.Participantsreportedthelanguagestheyknow,theirageofacquisition,

andthelengthoftimespeakingthoselanguages.Anyparticipantswithanageof

acquisitionof5yearsoldorearlierwereclassifiedashavingearlysecondlanguage(L2)

experience.33.8%ofparticipants(216total)reportedspeakingatleastonelanguageother

thanEnglish,while7.7%(49)hadearlyL2experience.AmongparticipantsinExperiment

1,inwhichparticipantswereexposedtoFrenchspeakers,6.7%(30)reportedknowing

someamountofFrench.AmongtheparticipantsinExperiment2,whowereexposedto

HindiandHungarianspeakers,nonereportedknowingHindiorHungarian.

Overall,participantswhohadanyL2experienceshowedameanlegalityadvantage

(i.e.,falserecognitionratesforlegalstimuliminusfalserecognitionratesforillegalstimuli)

of15.8%(CI[13.6%,18.1%]),andanoverallfalserecognitionrate,regardlessoflegality,of

61.0%(CI[58.2%,63.6%]);participantswithnoL2experienceshowedalegality

advantageof14.7%(CI[13.1%,16.4%])andafalserecognitionrateof61.5%(CI[59.5%,

63.6%]).ParticipantswithearlyL2experience,ontheotherhand,showedan18.9%

legalityadvantage(CI[14.6%,23.0%])and57.3%falserecognitionrate(CI[51.5%,

62.7%]);participantswithlateornoL2experienceshoweda14.8%legalityadvantage(CI

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[13.4%,16.2%])and61.7%falserecognitionrate(CI[60.0%,63.3%]).Listenerswith

FrenchexperienceinExperiments1AandBshoweda13.1%legalityadvantage(CI[6.3%,

16.5%]),whilelistenerswithnoFrenchexperienceinExperiments1AandBshoweda

15.6%legalityadvantage(CI[13.1%,16.6%]).

Mixed-effectsregressionswereusedtoassessdifferencesbasedonL2experience.

SeparatemodelswererunforearlyL2experience,anyL2experience,andFrenchL2

experience.ForearlyL2andanyL2experience,datawaspooledoverbothexperiments;

forFrenchL2experience,onlydatafromExperiment1wasincluded.Thesemodelsdidnot

showaneffectofL2experienceonthelegalityadvantage,astherewerenosignificant

interactionsbetweenthelegalityandL2experienceterms.Moreover,therewereno

significantmaineffects(i.e.,overalldifferencesinfalserecognitionrates)basedonL2

experience.

Basedontheseresults,itdoesnotappearthatparticipantswithL2experiencemade

strongerinferencesaboutthephonotacticgrammarsofspeakersbasedonthespeaker’s

languagebackgrounds.Thissuggeststhatarelativelysmalldegreeofexposuretonon-

nativephonotacticsisrequiredtomakeinferencesabouttalker’sphonotacticgrammars

basedontheirlanguagebackground,aslistenerswithoutextensiveL2experiencedoso.

Thisisnotsurprisinggivenlisteners’sensitivitytonon-nativephonotactics,evenininfants

asyoungas9-months-old(MattysandJusczyk,2001).Listenersalsotakeintoaccount

talkerphonotacticswhenjudgingspeakeraccentedness.Whenlistenershearspeechinthe

speaker’sL2,sequencesthatarelegalinthespeakers’nativelanguage(L1)aredeemedless

accentedthansequencesillegalinthespeakers’L1(Park,2013).Inotherwords,

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monolinguallistenersarehighlysensitivetonon-nativephonotactics,andarelikelyto

attendtosuchnon-nativepatternswhentheyappearintheinput,evenifthatinputis

relativelylimited.Thatsaid,therewereanumberoflimitationstothecurrentanalysisof

listenerlanguagebackground:first,listenersself-reportedtheirownlanguagebackground,

andwerenotaskedtoassesstheirownproficiency(althoughfluencyself-assessmentsmay

notbeentirelyreliable;Tomoschuk,Ferreira,&Gollan,2018).Thismeanstherewaslikely

awiderangeofproficiencylevelswithinlistenerswithL2experience.Second,therewasa

relativelysmallnumberoflistenerswithL2experience(especiallyearlyL2experience),

whichmayhaveresultedintoosmallofasampletodrawdefinitiveconclusions.Future

workshouldinvestigatetherelationshipbetweenlistenerlanguagebackgroundand

inferencesaboutphonotacticvariationdirectly,bycomparingbilingualandmonolingual

populations.

2.7. GeneralDiscussion

Recentresultsfromtheperceptualadaptationliterature(e.g.,LiuandJaeger,2018)

suggestthatlistenersusetheirpastexperiencetouncovertheunderlyingstructurethat

generatesvariationinspeechforms,andmakecausalinferencesbasedonthisstructure

whenexposedtonovelinput.Inthecaseofphonotactics,thereismassivevariation

betweenthephonotacticsystemsofdistinctlanguages,andrelativelylittlevariationwithin

asingledialect.Ourpredictionthatlistenerswouldleveragethispastexperiencewith

phonotacticvariationtomakeinferencesaboutnovelphonotacticconstraintsduring

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adaptationwaslargelyconfirmedinthreeexperiments.Experiments1AandBfoundahigh

degreeofadaptationtonovelphonotacticconstraintsbyEnglishlistenerswhentalkers

differedinlanguagebackground(Frenchvs.English).Incontrast,adaptationwasmoderate

whentalkerssharedanon-nativelanguagebackground(twoFrenchtalkers)orrelatively

lowwhentalkerssharedanativelanguagebackground(twoEnglishtalkers).Experiment2

showedthatthehighdegreeofadaptationincaseswheretwospeakersdifferintheir

languagebackgroundgeneralizestonon-nativelanguages(Hindivs.Hungarian)aswell.

Thispatternofresultssupportsthehypothesisthatlistenersmakedistinctionsbetween

non-nativephonotacticgrammars,andusethisinformationwhenmakinginferencesabout

whetherornottalkerssharedaphonotacticgrammar,althoughfurtherreplicationis

necessarytoconfirmthatthisisreliableacrossarangeoftalkers.

Whilelearningwasstrongerwhentalkersdifferedinlanguagebackground,learning

alsooccurredwhentalkerssharedalanguagebackground.Wearguethatthemore

confidentlistenersarethattwotalkersdifferintheirlanguagebackground,thegreater

adaptationwillbe;conversely,whenlistenersareconfidentthatthetalkerssharea

languagebackground,adaptationwillbelower.Whenlistenersareexposedtotwonative

Englishtalkers,forexample,wepredictedtheywouldbehighlyconfidentthatthetwo

talkerssharealanguagebackground(andthereforeaphonotacticgrammar),andwould

notadapt.Surprisingly,listenerswereabletoadaptinthiscondition,incontrastto

previousworkreportingnullresults(Onishietal.,2002).Listeneradaptationwaslowestin

thiscondition,however,suggestingthatlistenershadastrongpriorbeliefthatthetwo

Englishtalkerswouldhavesimilarphonotacticsrelativetootherpairsofspeakers.It

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appearstheevidencethatthetwotalkerssharedalanguagebackground,intheformof

theirsimilarphonetics,wasn’tenoughtoentirelyovercometheevidencetothecontrary.

Thisincludesthedifferentphonotacticpatternsexhibitedbyeachtalker;thefactthat

listenerswerelisteningtonon-nativewords;andthatasingleparticipantneverheardboth

talkersproducethesameword.

Theeffectofconfidenceconcerningtalkerlanguagebackgroundismoreacutewhen

twonon-nativetalkerssharethesamelanguagebackground,astheydidintheNon-Native

Sharedcondition.Here,wefoundagreaterdegreeofadaptationrelativetotheNative

Sharedcondition.Thisislikelyduetotheasymmetrybetweenlistenerknowledgeofnon-

nativevs.nativephonetics.NativeEnglishlistenershavelessknowledgeoftheFrench

phoneticsystemthantheEnglishone;thereforewhilethelistenersmayperceivetwo

Frenchspeakersasphoneticallysimilar,listenerswon’tbeasconfidentastheyarefortwo

Englishspeakers.

2.7.1. PhonotacticsandL2Acquisition

Whyisphonotacticadaptationsorapid,robust,andflexible?Intheseexperiments,

listenerswereabletosimultaneouslyadapttotwodistinct,complex(i.e.,second-order)

phonotacticconstraintswithinasingleshortexperimentalsession,showingsensitivityto

differentnon-nativelanguagesandevenindividualspeakers.Onepossibilityisthat

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phonotacticsareacriticaltoolintheearlieststagesofL2acquisition.7Thismaybebecause

phonotacticconstraintsguidespeechperceptionbylimitingthenumberoflexicaland

phonologicalcandidateslistenershavetoconsider(e.g.,listenersperceiveambiguous

soundsastheoptionthatresultsinalegal,ratherthanillegal,sequence;Massaroand

Cohen,1983).Thismaybeparticularlyimportantwhenspeechperceptionislessaccurate

intheearlystagesofacquisition.Phonotacticsalsoactasanimportantcueinword

segmentation(McQueen,1998),whichinturnisaprecursortolexicalacquisition.Indeed,

someevidencesuggeststhatadultlistenerslearnnovelL2wordswithhighphonotactic

probabilitymoreeasilythanthosewithlowprobability(Storkel,Armbrüster,&Hogan,

2010).

Forthelearner,adaptingtosubsetphonotacticsappearstobefairlyeasyrelativeto

othertypesofadaptation(e.g.,acquiringperceptualdistinctionsbetweentwoL2sound

categoriesthatassimilateintoasingleL1category;e.g.,Best,McRoberts,andGoodell,

2001).Inotherwords,whenthelistenerisfacedwiththeoverwhelmingprospectof

acquiringandunderstandinganunfamiliarlanguage,adaptingtothelanguage’ssubset

phonotacticsmayserveasacognitivelyinexpensiveadjustmentthataidslistenerswith

someofthemostimportantearlytasksofacquisition:speechperception,word

segmentation,andlexicalacquisition.Ifthisisthecase,wewouldpredictthatlearnerswho

7Thismaybeparticularlytrueforthetypeofsubsetphonotacticconstraintslistenerswereexposedtointheseexperiments(i.e.,restrictionsonsequencesthatarelegalinthelistener’sL1),whichdonotpresentthesameperceptualissuesassupersetphonotactics(i.e.,difficulttoperceivesequencesthatareillegalinthelistener’sL1,suchas[dl]inwordonsetforEnglishlisteners;seeDupoux,etal.,1999).

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areabletomoresuccessfullyadaptinphonotacticadaptationexperimentswouldalsobe

moresuccessfulinearlyL2acquisition.

It’salsopossibletheseadjustments,atleastinperception,areshort-lived,which

mayexplainthespeedwithwhichtheyaremade:earlyinacquisition,learnersmayneedto

readjustwitheachexposuretothenon-nativelanguage.Finally,thereisthequestionof

whylistenerscanlearnmultiplenon-nativephonotacticgrammarssoquickly.Ofcourse,we

knowthismustbepossibleinthelongterm,sincemultilingualspeakershaveaccessto

threeormoredistinctphonotacticgrammars.Furthermore,thismaybeaparticularly

importantskillincontextswithlanguagecontactoccurringbetweenmultiplelanguages.

2.7.2. AccentDetection

Listenersarecapableofmakingremarkablyfine-graineddistinctionsinnon-native

accentdetection(AtagiandBent,2013).However,incaseswherelistenersareexposedto

singlewordswithsubsetphonotactics,asinthecurrentexperiments,thisisahardertask

(Park,2013).Howwerelistenersabletodothis,particularlyinExperiment2,inwhich

theyweretaskedwithdistinguishingbetweentwonon-nativeaccents?Onepossibilityis

thetypeofcomparisonlistenershadtomakeinthecurrentexperimentswaseasierthan

thoseinpreviousstudies.Inmanyaccentdetectionstudies,listenersaregivenanauditory

freeclassificationtask,inwhichtheycomparealargenumberofdifferentaccented

speakersatonceonagradienttwo-dimensionalscale(e.g.,AtagiandBent,2013).Whilethe

highnumberofdifferentaccentsincreasesthedifficultyofthistask,listenersareallowed

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totakeaslongastheywantandre-listentoaudiosamplesofeachspeaker.Otherstudies

useatwo-alternativeforcedchoicediscriminationtask,inwhichlistenersarepresented

withanativeandnon-nativespeakerproducingthesameitemandmustdistinguish

betweenthem(e.g.,Park,2013).Inthecurrentstudy,thelistener’staskislessdemanding

thanthesepreviousstudies:listenersonlymust(implicitly)decidewhethertwospeakers

havedifferentaccents,notwhichoneisthenativevs.non-nativespeaker.Moreover,only2

languagesatatimeareinvolved.Finally,listenersdonothavetodecidewitheachitem

whichspeakerisnativeandwhichisnon-native;theyareabletobuildtheirrepresentation

ofthespeaker’slanguagebackgroundoverthecourseoftheexperiment.

2.8. Conclusion

Inthreeexperiments,wehaveshownthatlistenersusetheirpriorexperiencewith

phonotacticvariation—thatlanguagevaryintheirphonotacticsmuchmorethanindividual

speakersofthesamedialect—toguidetheiradaptationtonovelphonotacticconstraints.

Listenersevaluatetheunderlyingstructuregeneratingphonotacticvariation,andexhibita

largedegreeofadaptationtosystematicsourcesofphonotacticvariation(i.e.,listenerswho

differintheirlanguagebackground),andasmallerdegreeofadaptiontoincidentalsources

ofvariation(i.e.,listenerswhosharealanguagebackground).Thiseffectextendsto

differencesbetweendifferentnon-nativelanguages.Together,theseresultsilluminatea

corelinguisticability:appropriatelyadaptingtoourdynamiclanguageenvironmentbased

onourpriorexperience.

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3. Study2

3.1. Introduction

Speechisproducedwithahugeamountofvariationbetweentalkersandcontexts.

Toeffectivelycomprehendtheirinterlocutors,speakersmustcontinuallyadapttonovel

speakersandcontexts,drawingontheirexperiencefromsimilarsituationsinthepast.

Adaptationisnotlimitedtocomprehension,however—communicationisatwo-waystreet,

withspeakerstradingoffproducingandcomprehendingspeech.Speakersnotonlymodify

theirpredictionsofwhattheyexpecttohear;theyalsomodifytheirownspeech,imitating

andaligningthemselveswiththephoneticcharacteristicsoftheirinterlocutorin

spontaneousspeech(e.g.,Pardo,2006)orwhileshadowingamodeltalker(e.g.,Goldinger,

1998).

Phoneticimitationislikelymotivatedbyacomplexmixtureofsocialand

communicativefactors(Pardo,Urmanche,Wilman,&Wiener,2017),butitisonlymade

possiblebythesystematicityofinter-speakervariation.Imitatinganinterlocutor—either

tobringoneselfinclosersocialalignmentwithaninterlocutorinapositionofpower(e.g.,

Giles,1973)ortosimplifylanguageprocessingforbothspeakersinadialogue(e.g.,

PickeringandGarrod,2004)—onlyhasutilitybecauseindividualspeakersvary

systematically,showingconsistencyfromoneutterancetothenext.Ifspeakersvaried

freely,suchimitationwouldbringyounoclosertoyourinterlocutor’sspeech.

Inadditiontospeakersadaptingtothephoneticfeaturesofinterlocutorsandmodel

talkers,inexperimentalsettingsspeakersalsoadapttheirspeechproductionsystemsto

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reflectnovelphonotacticconstraintsembeddedinlaboratoryspeechortext(e.g.,Delletal.,

2000;Onishi,Chambers,&Fisher,2002).Theseexperimentalconstraintsareoften

arbitrary(e.g.,[n]isconstrainedtoonsetposition;[f]isconstrainedtocodaposition)and

are,bydefinition,notcharacteristicofaspeaker’snativelanguage.Intonguetwister

paradigms,forexample,participants’speecherrorsreflectthephonotacticconstraintsof

thelaboratorytexttheyareexposedto(e.g.,errorsresultingin[n]rarelyappearincoda

position).

Inthisstudy,weexplorehowthedifferencesinthestructureofvariationfor

phoneticsandphonotacticsmayresultindifferencesinadaptation.Whileadaptationtothe

phoneticpropertiesofaninterlocutorismotivatedbyspeakers’priorexperiencewiththe

systematicnatureofinter-speakervariation,phonotacticconstraintsvarylittleatthe

individuallevel.Instead,phonotacticsvaryextensivelyatthelanguage-anddialect-wide

level,withdifferentlanguagevarietiesexhibitingabroadrangeofpossiblesyllable

structuresandsoundsequencesnotfoundwithinlanguagevarieties.

Weexpectthisdifferenceinthestructureofvariationforphonotacticsversusthat

forphoneticstoresultindifferencesbetweenphoneticandphonotacticadaptation,aswe

sawinspeechperceptioninStudy1.Wearguethatspeakersmakecausalinferencesabout

thesourceofphonotacticvariationwhenadapting(e.g.,LiuandJaeger,2018),guidedby

theirpriorexperiencewithvariation:thattalkerswithinalanguagevarietyshareasingle

phonotacticgrammar,whiletalkerswhodifferintheirlanguagevarietiesdonot.Assuch,

wepredictthatwhenspeakersencountertwotalkerswithdifferingphonotactics,theywill

onlyadapttoeachtalker’sphonotacticgrammariftheybelievethosetalkersdonotsharea

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languagebackground.ThishypothesisisconsistentwithOnishietal.(2002),whofound

thatinaspeededrepetitiontask,participantswereabletolearnsecond-orderconsonant

constraintsconditionedonsurroundingvowels,butnotconstraintsconditionedontalker

identity(bothtalkerswerenativeEnglishspeakers).

Weexaminethisquestionusingamodifiedtonguetwisterparadigm.Oneachtrial,

participantswillfirstshadowamodelspeakerproducingastringoffoursyllables,andthen

repeattheirproductionsagainwithorthographicsupport(previoustonguetwister

experimentshavepresentedthetwisterinorthographicformonly,withtheexceptionof

Smalle,Muylle,Szmalec,&Duyck,2017).Thestringsofsyllablesassociatedwitheach

modeltalkerwillreflectdifferentphonotacticconstraints.Thelanguagebackgroundofthe

modeltalkerswasmodulatedindifferentconditions,withmodeltalkerseithernative

speakersofGermanorEnglish.ThreeofthefourconditionsmirrortheconditionsinStudy

1,withtwotalkersthateithershareordifferintheirlanguagebackgrounds:NativeShared

(twomonolingualEnglishmodeltalkers),Non-NativeShared(twonativeGermanmodel

talkers),andDifferent(oneGerman,oneEnglishtalker).Inaddition,aVowelconditionwas

includedasataskcontrol,ensuringthatresultsfrompreviousworkarereplicated(e.g.,

Gaskell,Warker,Lindsay,Frost,Guest,Snowdon,&Stackhouse,2014;Smalleetal.,2017;

Warker,2013;Warker&Dell,2006)despitechangestothetask.IntheVowelcondition,

participantsareexposedtoasinglemodeltalker,andlearnasecond-orderconstraintin

whichconsonantrestrictionsareconditionedontheneighboringvowel(e.g.,[ɛ]canbe

followedby[m]andprecededby[n];thereverseistruefor[ɪ]).Adaptationismeasuredby

analyzingtheerrorsofparticipants:iferrorsinvolvinganexperimentallyconstrained

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segmentresultinlegalsyllables(i.e.,syllablesthatfollowthephonotacticpattern

embeddedintheinput)morethanillegalsyllables,itsuggestsparticipantsareadapting.

Ifthesameprinciplesforadaptationapplyinproductionastheydoinperception,

weexpectasimilarresulttowhatwasfoundinpreviousperceptionexperiments:ahigher

degreeofadaptationintheDifferentconditionthaninthesharedconditions.Atamore

granularlevel,wemayexpectmoderateadaptationintheNon-NativeSharedcondition,and

alowdegreeofadaptationintheNativeSharedcondition,mirroringtheresultsfrom

perception.

3.2. Background

3.2.1. Phonotacticlearninginspeechproduction

Overthepasttwentyyears,researchershaveexploredphonotacticadaptationusing

thetonguetwisterparadigm(Anderson,Holmes,Dell,&Middleton,2019;Delletal.,2000;

Gaskelletal.,2014;Goldrick,2004;Goldrick&Larson,2008;Kittredge&Dell,2016;Smalle

etal.,2017;Taylor&Houghton,2005;Warker,2013;Warker&Dell,2006;Warkeretal.,

2008;Warker,Xu,Dell,&Fisher,2009).Inthetonguetwisterparadigm,errorsareelicited

byhavingparticipantsquicklyrepeatastringofnonsensesyllables.Thesesyllablesfollow

anartificial,experimentalphonotacticconstraint,suchas“syllablesbegin,butdonotend,

in[n];viceversafor[f]”.Inaddition,twistersalsoincludesegmentsthatareconstrainedin

theparticipant’snativelanguage,suchas[ŋ],whichisconstrainedtocodapositionin

English.Speecherrorsvirtuallyneverviolatesuchlanguage-widecategoricalphonotactic

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constraints—thisissometimesreferredtoasthephonotacticregularityeffect(Fromkin,

1971).InEnglish,forexample,producingfipwhenthetargetissipisapossibleerror,but

ngipforsipisanextremelyunlikelyerror.Otherconsonantsintheexperimentare

unconstrained,appearinginbothonsetandcodaposition.Suchunconstrainederrorstend

tomaintaintheirsyllableposition(Nooteboom,1969):forexample,fikfip,inwhich[f]

maintainsitspositionintheonsetofthesyllable,isamorelikelyerrorforthetarget

sequencefiksipthanfiksif,inwhich[f]switchestothecodaposition.Intonguetwister

experiments,thissyllablepositioneffect—whichholdsinroughlythree-quartersof

errors—servesasabaselineforexperimentallearningeffects.Learningismeasuredasthe

degreetowhicherrorsinvolvingexperimentallyconstrainedconsonantsmaintaintheir

syllablepositionaboveandbeyondthesyllablepositioneffectforunconstrained

consonants.Inpreviousexperiments,adaptationtothenovelconstraintcauseserror

patternsforexperimentallyconstrainedconsonantstoresembleerrorpatternsoflanguage

constrainedsyllables,oftenmaintainingtheirsyllableposition95%ofthetimeormore

(e.g.,Delletal.,2000).

Phonotacticadaptationexperimentshaveshownthatspeakersarealsosensitiveto

first-versussecond-orderconstraints,witheachtypeofconstraintshowingdistinct

learningpatterns.First-orderconstraintsaredependentonlyonsyllableposition(e.g.,“[n]

isconstrainedtoonsetposition;viceversafor[f]”);second-orderconstraintsare

dependentontwofactors(e.g.,“ifthevowelis[ɪ],[n]isconstrainedtoonsetand[f]is

constrainedtocoda;ifthevowelis[ɛ],viceversa”).Suchsecond-orderconstraints

naturallyoccurwithintheworld’slanguages.InEnglish,forexample,[b]appearsinonset

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positionprecedingthevowel[i](asinbeet),butisunattestedincodapositionfollowing[i]

(e.g.,teeb;KesslerandTreiman,1997).Previousworkhasshownthatsecond-order

constraintsarenotlearnedasthoroughlyasfirst-orderconstraints,witherrorslesslikely

tomaintaintheirsyllableposition.Inaddition,learningeffectsforsecond-orderconstraints

donotappearduringthefirstexperimentalsession(seeWarker,2013).Morespecifically,

sleepconsolidationappearstoplayacriticalroleintheacquisitionofsuchconstraints,as

participantsrequiresleepininterveningperiodsbetweensessionstoshoweffectsof

learning(Gaskelletal.,2014;Warker,2013).Thecurrentstudyexposesparticipantsto

second-orderconstraints,withconsonantpositioneitherdependentonvowelormodel

talkerlanguagebackground,dependingonthecondition.Assuch,weincludethree

experimentalsessions,eachondifferentdays,toensureparticipantsareabletoconsolidate

theconstraints.

3.2.2. Causalinferenceinphonotacticadaptationinproduction

Wehypothesizethatadaptationisspurredincontextsinwhichspeakersare

interactingwithtalkersthathavedifferentlanguagebackgrounds.Ifthisisthecase,why

haveparticipantsinprevioustonguetwisterexperimentsadaptedatall,whenthey’re

simplyreadingtwistersaloudandnotinteractingorshadowingotherspeakers?Asnoted

inStudy1,Warker(2013)foundthatparticipantsmaintaintheexperimentallylearned

phonotacticconstraintsaslongasoneweekafterinitialexposure,despitethemassive

interveningexperiencewithEnglishcontrarytosuchconstraints.Participantsalsolearn

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thenewconstraintsrapidly,despitealifetimeofexperiencesuggestingsuchconstraints

arenotapartoftheirnativelanguage.Warker(2013)proposesamechanisticaccountfor

suchlearning,inwhichparticipantscreateacopyoftheirgeneralphonotacticgrammarto

useinexperimentalsettings.Intheexperiment,thecopyisupdatedtoreflectonlythose

featuresoftheexperimentalcontextthatarenottrueofthegeneralphonotacticgrammar.

Aremainingquestioniswhyspeakerscreatethecopyinthefirstplace—whydo

speakershavetheadaptiveabilitytoquicklymodifytheirphonotacticsinthisway?Of

course,speakersdonotregularlyfindthemselvesinpsycholinguisticexperiments,sothis

doesnotseemlikeapossiblemotivationforthisadaptiveability;moreover,speakers’

nativelanguagephonotacticsarelikelyrelativelystable(Pierrehumbert,2001),suggesting

phonotacticadaptationisnotdrivenbydifferencesbetweenspeakerswithinone’snative

language.Wearguethatintonguetwisterexperiments,asintheperceptualadaptation

exploredinStudy1,participantsarerecruitingtheirsecond-language(L2)learning

facultiestoadapttonon-nativephonotacticconstraints.Inthehighlyartificiallaboratory

setting,inwhichparticipantsareexposedtononsensesyllablesthatarenotpresentedina

semanticallymeaningfulnativelanguagesetting,participantsmaydetectthattheyareina

non-nativelanguagecontext.Detectingsuchchangesincontextisacriticalaspectof

learninginamulti-contextenvironment(Qian,Jaeger,&Aslin,2012).Moreover,wehave

strongevidencethatlearnersareabletodetectdifferentphonotacticenvironmentsand

constructmultiplephonotacticgrammarsintheformofmultilingualspeakers.Multilingual

learnersareexposedtoconflictingphonotacticpatternsinacquisition,andmustseparate

evidencefordifferentconstraintsbasedonthelanguagecontextinwhichtheyappear

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(althoughbilinguals’phonotacticgrammarsarenotentirelyseparate;seeCarlson,

Blasingame,Goldrick,&Fink,2016).Learnerslikelydothisbyleveraginganumberof

differentcues,suchasdifferinglexicalitems,phonetics,prosody,talkervoices,andother

factors(e.g.,Bosch&Sebastián-Gallés,2001;Weiss,Gerfen,&Mitchell,2009).Inthisstudy,

wepredictparticipantswillinfermultiplelinguisticcontextsbasedonthephonetic

differencesbetweenthenativeandnon-nativemodeltalkers.

3.2.3. CurrentStudy

Recentevidenceintonguetwisterstudiessuggeststhatspeakersarerelatively

insensitivetohigh-levelinferencesaboutthesourcesofvariation,however.Delletal.

(2000)informedsomeparticipantsoftheexperimentalconstraintstheywouldbeexposed

to,andfoundlearningwasunaffectedbypriorknowledgeoftheconstraint(seealsoSmalle

etal.,2017;Warker&Dell,2006).Andersonetal.(2019),inatonguetwisterparadigm,

exposedlearnerstoafirst-orderconstraintandthenreversedthephonotacticconstraint

partwaythroughtheexperiment,beforereversingitbackagaininthefinalblock.If

participantsweresensitivetothechangeincontext(i.e.,thereversalofthephonotactic

constraint)andthesourceofthevariation,theyshouldhavebeenabletorapidlyreverse

theconstraint,andlearnthereversedconstraintfasterthantheoriginalconstraint,given

thatthereversedphonotacticinvolvedthesametargetconsonants,simplyinflipped

syllabicposition.Instead,participantslearnedthereverseconstraintmoreslowlythanthe

original,suggestingthatphonotacticlearningisincremental,andresistanttocausal

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inferencesaboutchangesincontext.Andersonandcolleaguesarguethatphonotactic

adaptationisinternaltotheaspectoftheproductionsystemthatconstructssyllables,and

“notverycognitivelypenetrable”fromoutsidesystems.Moreover,thelearningsystemmay

bedomaingeneral:participantsshowremarkablysimilarpatternsfor“phonotactic”

learninginbutton-pushingtasks,inwhichdifferentfingersareassigneddifferent

“consonants”(Andersonetal.,2019;Rebei,Anderson,&Dell,2019).Thisfurthersuggests

thatlearnersmaybeinsensitivetolanguage-specificinferences,suchasthosebasedon

accent.Finally,adaptationintheproductionsystemmaysimplybemorecognitivelycostly

thanadaptationinperception,andthereforeslowerandmoreconstrained(Samuel,2011).

Anaccountinwhichspeakersareinsensitivetotop-downinferencesaboutthesourceof

variation,motivatedbytheseprevioustonguetwisterexperiments,wouldpredictlearners

areentirelyunabletodivideinputbetweenmodeltalkersandformmultiplephonotactic

grammars.ThisaccountthereforepredictsadaptationinthebaselineVowelconditionin

thecurrentstudy.AdaptationintheDifferentcondition,however,wouldsuggestthat

inferencesbasedonlanguagecontext,specifically,mayhaveaprivilegedstatusoverother

lessrelevanttypesofinformation.

Themeasureofinterestintonguetwisterexperimentsistherateatwhicherrors

maintainsyllableposition.Ifparticipantsareadaptingtotheexperimentalconstraint,they

shouldbemorelikelytomakeerrorsthatmaintainsyllablepositionforexperimentally

restrictedconsonants(i.e.,errorsthatfollowthephonotacticconstraint)thanfor

unrestrictedconsonants.Adaptationwillthereforebeindicatedbyahigherproportionof

errorsmaintainingtheirsyllablepositionforconstrainederrorsthanunconstrainederrors.

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Forsecond-orderconstraints,adaptationshouldspecificallyappearinthesecondandthird

experimentalsessions,followingpreviousresults(e.g.,WarkerandDell,2006).

WepredictahighdegreeofadaptationinthebaselineVowelcondition,following

resultsfrompreviousexperiments.IfwedonotreplicatepreviousstudiesintheVowel

condition,itmayindicateissueswiththecurrentdesign(especiallyhavingtwisters

presentedauditorilyaswellasorthographically).Wealsopredictahighdegreeof

adaptationintheDifferentcondition,inwhichmodeltalkersdifferintheirnativelanguage

backgrounds,reflectingspeakers’useoftheirpriorexperiencewithphonotacticvariation

toadapttonovelconstraints.BothSharedconditions,ontheotherhand,shouldshowalow

tomoderatedegreeofadaptation,giventhatbothmodeltalkerssharealanguage

background.Morespecifically,wemayfindlowadaptationintheSharedNativecondition,

andmoderateadaptationintheSharedNon-Nativecondition,aswedidinperceptionin

Study1.Suchintermediateadaptationmaybeduetospeakers’asymmetricknowledgeof

nativevs.non-nativelanguages—speakersarelikelyquitecertainwhentheyareexposed

totwonativespeakersoftheirnativelanguagethatthetwospeakerssharealanguage

background,butlikelymuchlesscertainwhentheyareexposedtotwonon-native

speakers.

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Table3.1.Summaryofconditions,alongwithmodeltalkerlanguagebackground,vowels,gender,anddegreeofadaptation.

NativeShared Non-NativeShared

Different Vowel

Modeltalkers 2English 2German 1English,1German

1Englishor1German

Vowels [ɛ] [ɛ] [ɛ] [ɛ]and[ɪ]PredictedDegreeofAdaptation

Low Low-to-moderate

High High

3.3. Methods

Thedesignandanalysisoftheexperiment—includingpredictions,numberof

participants,stimulusdesign,andmodelstructure—weredefinedbeforedatacollection,

unlessotherwisenoted,inapre-registrationontheOpenScienceFoundationplatform

(osf.io/uryc5/).

3.3.1. Participants

Sixteenparticipantswererecruited,allnativeAmericanEnglishspeakersfromthe

NorthwesternUniversitycommunitywithnospeechorhearingimpairments.The

experimentconsistedof3one-hoursessions,eachonadifferentday.Eachsessiontook

placenofurtherthanaweekapart.Participantswerepaid$40:$10foreachofthefirsttwo

sessions,and$20forthefinalsession,toincentivizeparticipantstoattendallthree

sessions.Participantswererandomlyassignedtodifferentconditions.

Beforetheexperimentbegan,participantscompletedaself-reportedlanguage

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backgroundquestionnaire,reportinganysecondorthirdlanguages,aswellastheirageof

acquisitionandlengthofspeakingforeachlanguage.

3.3.2. Materials

Participantswereexposedtosecond-orderconstraintsinallconditions:inthe

NativeShared,Non-NativeShared,andDifferentconditions,constraintswereconditionon

modeltalkeridentity(e.g.,ifTalkerAisthemodeltalker,[m]isconstrainedtocoda

positionand[n]isconstrainedtoonsetposition;theconverseistrueforTalkerB).Inthe

Vowelcondition,participantswereexposedtoasecond-orderconstraintsimilartopast

experiments,inwhichthepossiblepositionsofexperimentallyconstrainedconsonantsare

conditionedonthevowel.Fourmodeltalkerswereincluded:onemaleandonefemale

Germanspeaker,andonemaleandonefemaleEnglishspeaker.IntheVowelcondition,

participantswereexposedtoasinglemodeltalker;adifferentmodeltalkerwasassignedto

eachparticipant.IntheNativeSharedcondition,participantswereexposedtobothEnglish

modeltalkers;intheNon-NativeSharedcondition,halfoftheparticipantswereexposedto

bothGermanmodeltalkers.IntheDifferentcondition,participantswereexposedtoone

GermanmodeltalkerandoneEnglishmodeltalker,whodidnotshareagender(e.g.,male

GermantalkerandmaleEnglishtalker).

Followingpreviousstudies,stimuliconsistedofCVCnonsensesyllablesmadeup

fromtwovowels([ɪ]and[ɛ])andeightconsonants([f],[p],[k],[t],[m],[n],[ŋ],[h]).While

mostpreviousexperimentsused[g]and[s],[p]and[t]wereusedinsteadtoavoid

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phonotacticconstraintsinGerman:word-finally,[g]inGermanisproducedas[k]dueto

word-finaldevoicing,and[s]isproducedas[z]inword-initialposition.[æ]isalsousually

used,butwasreplacedwith[ɛ]because[æ]isnotavowelofGerman.[m]and[n]servedas

theexperimentallyrestrictedconsonantsfollowingpreviousexperiments(Delletal.,2000;

Warker,2013;WarkerandDell,2006).Anothersetofconsonants([k],[p],[t],[f])was

unrestricted,appearingfreelyinanyposition.[ŋ]and[h]servedasthelanguage-wide

restrictedconsonants,with[ŋ]illegalinonsetand[h]illegalincoda.

Eachmodeltalkerrecordedasetof96uniquetonguetwisterstobeusedinthe

DifferentandSharedconditions(thesetwaskeptconstantacrossmodeltalkers).These

twisterswererandomlyconstructed,withtheexceptionofphonotacticconstraints:they

obeyedlanguage-wideconstraints,andhalfofthesetwistershad[m]inonsetand[n]in

coda,whiletheotherhalfhadthereversepattern.Thephonotacticpatternassignedtoeach

modeltalkerwascounter-balancedacrossparticipant.IntheDifferentandShared

conditions,participantswereexposedtoalternatingmodeltalkers(andtherefore

alternatingphonotacticconstraints)oneverytrial.The[ɛ]vowelwasusedineachofthese

twisters.Forexample,aparticipantinoneoftheSharedorDifferentconditionsmightbe

exposedtothefollowingtwotrials:

Trial1(Shared/Differentconditions)

TalkerA:fengmethepken

Trial2(Shared/Differentconditions):

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TalkerB:nengfekhempet

Notethatthepositionof[m]and[n]isdependentonthetalker,whichalternateseachtrial,

whilethevowelisconsistentbetweentrials.

Withtheexceptionofthealternation,thetwisterorderwasrandomized.Ineach

session,participantswereexposedtothesetof96twisters—halffromeach

talker/phonotacticconstraint—thenexposedtothesamesetagaininadifferentrandom

order,foratotalof192trials.Therewasnoindicationforparticipantsthattheywere

exposedtoasmallersettwice,ratherthanonelargeset.IntheVowelcondition,

participantsheardasinglemodeltalker,witheachtrialalternatingbetweenthe[ɪ]and[ɛ]

vowels,withthephonotacticconstraintalternatingbasedonthevowel.Forexample,a

participantintheVowelconditionmightbeexposedtothefollowingtwotrials:

Trial1(Vowelcondition)

TalkerA:tikminpifhing

Trial2(Vowelcondition):

TalkerA:kepnetfenghem

Notethatthepositionof[m]and[n]aredependentontheidentityofthevowel,which

alternateseachtrial,whilethetalkerisconsistentthroughouttheexperiment.

Eachmodeltalkerrecordedanadditional48twisterswiththe[ɪ]vowelforthe

Vowelcondition,withtheother48twistersre-usedfromtheotherconditions.

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3.3.3. Procedure

Participantswererecordedinasound-proofboothusingahead-mounted

microphone,wheretheyreadthetwistersfromacomputermonitorandheardtwisters

frommodeltalkersoverspeakers.Inaddition,participantsheardmetronomebeatsfrom

anearbudheadphoneplacedintheleftear.

Beforetheexperimentaltrialsbeganeachsession,participantscompleted4practice

trials,noneofwhichcontainedtheexperimentallyconstrainedconsonants.Practicetrials

includedthemodeltalkersthatwouldappearintheexperimentaltrials.Ineach

experimentaltrial,asequenceoffoursyllableswaspresentedtoparticipants(e.g.,femheng

ketnep).Intheslowrepetitionphaseofeachtrial,participantswereexposedtothe

sequencebeingreadbythemodeltalkerataslowpace(1syllable/second).Afterthe

modeltalkeraudiostoppedplaying,theorthographicrepresentationofthetwister

immediatelyappearedonthescreen,andparticipantsrepeatedthetwisterintimewiththe

modeltalker.Eightsecondsafterinitiatingthetrial(4secondsforthemodeltalker’s

productions,and4secondsfortheparticipantsrepetition),participantswerefreeto

advancetheexperimenttothefastrepetitionphase.Inthefastrepetitionphase,

participantsheardsixteenbeatsofametronomeatthespeedof2.5syllables/second.

Participantswereinstructedtowaitduringthefirst4beats,thenrepeatthefour-syllable

sequencethreetimesoverthefinal12beats.Afterallmetronomebeatswerefinished

playing,participantswerefreetoadvancetheexperimenttothenexttrial.

Afterthefinalsession,participantswereaskedaseriesofpost-experiment

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questionsbytheexperimenter:first,didyounoticeanythingnoteworthyaboutthe

speakers?Ifparticipantsdidnotbringupthenon-nativestatusofspeakersontheirown

(intheconditionsinwhichtheywereexposedtonon-nativespeakers),theywereaskeda

secondquestion:didyouthinkthespeakersyouheardwerenativespeakersofEnglishor

non-nativespeakers?Finally,ifparticipantsrespondedthattheyheardoneormorenon-

nativespeakers,theywereaskedtoguessthespeakers’nativelanguagebackgrounds.

3.3.4. Analysis

Adaptationwasstatisticallyverifiedusinglogisticmixed-effectsregressions.The

dependentmeasureinallmodelswasmaintenanceofsyllableposition.Thefirsttypeof

analysisfittedindividualmodelstothedatafromeachcondition.Fixedeffectsincludeda

contrast-codedfixedeffectofconsonanttype(i.e.,experimentallyconstrainedvs.

unrestricted)andacontrast-codedfixedeffectofexperimentalsession,inwhichsession1

wascontrastedwithsessions2and3.Aninteractiontermbetweensessionandconsonant

typewasalsobeincluded.Thisinteractiontermwouldindicateadaptationhadtakenplace,

withanincreasedmaintenanceofsyllablepositionforconstrainedconsonantsinsessions

2and3oversession1.Randomeffectswillincluderandominterceptsfortargetsyllable;

withonly4participantspercondition,therewasnotasufficientnumbertoincluderandom

effectsforparticipant.

Inacomparisonacrossconditions,amodelwasfittedtothedatafromtheDifferent

andSharedconditions(excludingtheVowelcondition).Thismodelincludedcontrast-coded

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fixedeffectsconsonanttype,session,andtheirinteraction,andrandominterceptsfor

targetsyllable.Inaddition,itincludedacontrast-codedfixedeffectofcondition,comparing

theSharedconditionswiththeDifferentcondition.Ifspeakersmaketop-downinferences

aboutlanguagebackgroundduringproduction,wewouldexpectasignificantinteraction

suchthattheeffectofconsonanttypeisstrongerintheDifferentconditionthaninthe

Sharedconditions.

Asecondcontrast-codedterm,comparingtheNativeSharedconditiontotheNon-Native

conditionandtheDifferentcondition(i.e.,conditionswithonlynativemodeltalksvs.those

withsomeorallnon-nativemodeltalkers),wasplannedbutultimatelynotincluded.

Finally,alternativeversionsofthewithin-conditionmodelsandbetween-condition

modelswerefittedtothedatajustfromsessions2and3.Thestructureofthesemodels

wereidenticaltopreviousmodels,withtheexceptionofsession,whichwasnotincludedas

afixedeffect.Modelswithoutsession1wereunplannedanalyses;theirpurposewasto

simplifymodelstructureandfocusonsessions2and3,wherewehadthestrongestprior

beliefthatadaptationwouldoccur.

3.4. Results

Recordingsweretranscribedforerrors.Errorsmadeupofconsonantsnotincluded

intheexperiment(N=64)werenotedbutexcludedfromtheanalysis;individualvowel

errorsweregenerallynotnoted,butifparticipantsmadesystematicvowelerrorsthiswas

noted.Errorswerecodedformaintainingsyllableposition.Forexample,ifthetarget

twisterwasfektephenmengandtheparticipantproducedtektephenmeng,the[t]errorin

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tekwascodedasmaintainingitsposition;iftheparticipantproducedfettephenmeng,the

[t]errorinfetwascodedaschangingitsposition.Everytwisterwastreatedasifithad

exactly4targetsyllables.Ifparticipantsproducedmoreorlessthan4syllables,participant

productionswerealignedwiththe4twistertargetsinthealignmentthatresultedinthe

fewesterrors.Errorswerealsocodedforraterconfidenceaseitherhighconfidence(i.e.,

verylikelyorcertainerror)orlowconfidence(i.e.,possible/moderatelylikelyerror).

Acrossallconditions,therewere48totalsessions(16participants,3sessionseach),

resultinginatotalof9,216trials(2304percondition)or110,592totalsyllables(27,648

percondition).Errorswerecodedby2coders;ofthe48total,onecodercompleted43

sessions,whileasecondcodercompleted6sessions.Onesession(2,304syllables)was

codedforreliabilitybybothcoders.Therewasanoverallagreementrateonthe

presence/absenceoferrorsfor99.3%ofallsyllables.Lookingatagreementononlythose

errorsidentifiedbytheprincipalcoder(N=27),therewas74.1%conditionalized

agreement,anumberinlinewithpreviousexperiments.

Atotalof3864errorswerediscovered,or3.5%ofallsyllables,anerrorratewithin

therangeofpreviousexperiments(althoughonthelowend;seeAppendixF).Ofthese,82

(2.1%)werecodedaslowconfidencebythetranscribers.Arelativelywiderangeoferror

rateswerefoundfordifferentconditions(seeTable3.2),butthatmaysimplyreflect

variationacrossparticipants(seeFigure3.1).

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Table3.2.Numberoferrorsanderrorratesbycondition.

Condition nErrors ErrorRateDifferent 928 3.4%NativeShared 1201 4.3%Non-NativeShared 1106 4.0%Vowel 629 2.3%

Figure3.1.Overallerrorratesbyparticipant.Colorsreflectexperimentalcondition.

Therewere807errorsonconsonantssubjecttolanguage-widephonotactic

constraints(i.e.,errorsresultingin[ŋ]and[h]).Ofthese,99.8%followedEnglish

phonotacticconstraintsandmaintainedtheirsyllablepositions.Therewere2,124errors

forunconstrainedconsonants([p],[t],[k],and[f]),whichmaintainedtheirsyllableposition

74.5%oftime,inlinewithpreviousexperiments.Ofthe933errorsforexperimentally

constrainedconsonants([m]and[n]),however,only50.2%oferrorsmaintainedtheir

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syllableposition.Thiswasasurprisingresult—evenifnolearningoccurredatall,

experimentallyconstrainedconsonantsshouldhave,allelsebeingequal,maintainedtheir

syllablepositionatasimilarratetounconstrainedconsonants.Closerinspectionofillegal

constrainederrorsrevealedthatalargeproportionconsistedofswapsbetween[m]and

[n]:for40.5%ofall[n]errors,thetargetwas[m],andfor32.7%ofall[m]errors,thetarget

was[n](seeTable3.3fortarget-errormatrix).Overall,swapsbetweennasalconsonants

occurredatadisproportionatelyhighrate:tabulatingtheproportionoferrorsthatwere

intendedforaspecifictargetconsonantforall64possibleerror/targetcombinations

revealedthat4ofthetop5error/targetcombinationswerenasalswaps.Thelocusforsuch

swapsmaybethatnasalpairsweremorephoneticallysimilaritythanotherconsonant

pairs;previousevidencefromtonguetwisterexperimentssuggestsphoneticsimilarity

(Wilshire,1999)andoverlappingphonologicalfeatures(Goldrick,2004)affectspeech

errors.It’sunclear,however,why[m]and[n]weremoreaffectedbyphoneticsimilarity

thanothersegments,asanumberofpreviousexperimentshaveincludedthesesegments

(seefollowingsectionforfurtherdiscussion).

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Table3.3.Target/errormatrixforallconsonantsandconditions.Targetsarecolumnsanderrorsarerows.TheNoTargetcolumnreferstoerrorsthatweremadeonextrasyllables(i.e.,whenaparticipantproducedmorethan4syllablesinasingletwister).Gradientcolor-codingreflectsthenumberoferrorsforagiventarget/errorcombination.

ftargets

htargets

ktargets

mtargets

ntargets

ŋtargets

ptargets

ttargets

NoTarget

ferrors - 69 85 44 19 12 133 33 29herrors 55 - 129 32 54 0 52 51 32kerrors 103 158 - 20 11 35 150 126 23merrors 24 18 22 - 119 99 50 12 20nerrors 16 39 27 231 - 188 13 34 21ŋerrors 10 0 22 106 231 - 8 12 13perrors 105 75 174 62 17 5 - 96 31terrors 44 57 167 9 35 3 163 - 31

Such[m]-[n]swapshadalargenegativeeffectonthemaintenanceofsyllable

positionbecause[m]and[n]targetsneveroccurredinthesamesyllablepositioninagiven

twister(i.e.,[m]-[n]swapswerealwaysillegal).Assuch,inadditiontoanalysesconducted

withthefulldataset,post-hocanalyseswerealsoconductedwith[m]-[n]swapsexcluded

fromthedatasettocontrolforthisphoneticsimilarityeffect(Goldrick,2004,followeda

similarprocedure).Thegoaloftheseanalyseswastocompareeffectsbetweenconditions,

oncephoneticsimilaritywascontrolled.Notethatwhileothernasalswapsinvolving[ŋ]

alsooccurredatadisproportionatelyhighrate,suchswapswouldnothavethesameeffect

onthesyllablepositioneffectbecause[ŋ]targetsalwaysoccurredincodaposition.Unlike

[m]-[n]swaps,nasalswapsinvolving[ŋ]andanothernasaldidnot,bydefinition,change

syllablepositions.Assuch,swapsincluding[ŋ]wereatnopointexcludedfromthedataset.

Inaddition,giventheissueswithperceptualsimilarity,low-confidenceerrorswere

excluded.

95

Thepercentageoferrorsthatmaintainedsyllableposition,splitbyexperimental

sessionandcondition,isshowninFigure3.2.Inwithin-conditionmodelsthatincludedall

sessions,thecriticalinteractionwasbetweentheconstrainttermandthesessionterm.No

suchinteractionsweresignificantforanyconditionexcepttheNativeSharedcondition,

whichwentintheoppositedirectionofadaptation(i.e.,thesyllable-maintenanceeffected

decreasedforexperimentallyconstrainedconsonantsinsessions2and3;seeAppendixG

forfullmodelresults).Contratoourpredictions,adaptationdidnotincreaseinlater

sessionswithineithertheVowelorDifferentconditions(seebelowfordiscussionofnull

resultforthebaselineVowelcondition).

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Figure3.2.Percentageoferrorsthatmaintaintheirsyllablepositionforconstrainedvs.unconstrainedconsonants,brokendownbysessionandcondition.Alldatavisualized,including[m]-[n]swaps.Errorbarsreflect95%confidenceintervaloverparticipant;however,notethatparticipantscontributeddifferentnumbersoferrorstoeachbar.

Inthebetween-conditionmodelthatincludedallsessionsandcomparedadaptation

intheDifferentconditiontotheSharedconditions,thecriticalinteractionbetween

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constraint,session,andconditionwasnotsignificant(seeTable3.4)8.Thissuggeststhat,

againstourprediction,adaptationtotheexperimentalconstraintdidnotincreasemorefor

theDifferentconditioninlatersessionsthanfortheSharedconditions.Inthebetween-

conditionmodelthatonlyincludedsessions2and3,however,thecriticalinteraction

betweenconstraintandconditionwassignificant,suggestingthatforthelatersessions

only,therewasalargeradaptationeffectintheDifferentconditionthanintheShared

conditions(seeTable3.5).Thisprovidesevidenceforastrongereffectofadaptationinthe

latersessionsoftheDifferentconditionthanintheSharedconditions,althoughitshouldbe

notedthiswasanunplannedanalysis.

Table3.4.Betweenconditioncomparison;allsessions;[m]-[n]switchesincluded.

FixedEffect Coefficient StandardError χ2(1) p(Intercept) 1.24 0.11

Constraint 0.3* 0.14 4.72 0.03Session 0.03 0.13 0.05 0.83Condition -0.18 0.19 0.85 0.36Constraint:Session -0.12 0.26 0.23 0.63Constraint:Condition 0.35 0.38 0.87 0.35Session:Condition 0.46 0.38 1.44 0.23Constraint:Session:Condition 0.9 0.77 1.36 0.24

RandomEffects

VarianceTargetSyllable

0.31

8Itshouldbenotedthatthiscriticalinteractionwasmarginallysignificant(p=0.07)whenlow-confidenceerrorswereexcluded,illustratingthesensitivityoftheeffecttovariousanalysischoices—seebelowforfurtherdiscussion.

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Table3.5.Betweenconditioncomparison;session1excluded;[m]-[n]switchesincluded


Constraint -1.12*** 0.15 58.39 <0.001Condition 0.05 0.19 0.06 0.8Constraint:Condition 0.81* 0.39 4.32 0.04

RandomEffects


0.42

Inthepost-hocanalysis,all[m]-[n]switcheswereremovedfromthedataset(see

Figure3.3).Thishasalargepositiveeffectonthesyllablemaintenanceeffectfor

experimentallyconstrainedconsonants(raisingitfrom50.2%to80.3%),bringingitmuch

closertothesyllablemaintenanceeffectforunconstrainedconsonants(74.5%).Inthe

within-conditionmodelsthatincludedallsessions,butexcluded[m]-[n]swaps,thecritical

constraint:sessioninteractionwasnotsignificantwithinanycondition.Thissuggeststhat

evenwhenremoving[m]-[n]swaps,thereisnoevidencethatsyllablemaintenance

increasesaftersession1moreforconstrainedconsonantsthanforunconstrained

consonants(seeAppendixGformodelresults).

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Figure3.3.Percentageoferrorsthatmaintaintheirsyllablepositionforconstrainedvs.unconstrainedconsonants,brokendownbysessionandcondition.[m]-[n]swapswereexcluded.Errorbarsreflect95%confidenceintervaloverparticipant;however,notethatparticipantscontributeddifferentnumbersoferrorstoeachbar.IntheVowelcondition,oneparticipantmadethemajorityoftheerrorsbuthadamuchlowermeanthanotherparticipants,resultinginaCIthatdoesnotoverlapwiththemeanforSession1,unconstrainederrors.

Inaseparatewithin-conditionanalysisthatexcludessession1,thecriticalmain

effectofconstraintwassignificantintheDifferentcondition(seeTable3.6),butnotinany

othercondition(seeAppendixG).Thissuggeststhatonce[m]-[n]swapswereremoved,

syllablepositionwasmaintainedatahigherrateforconstrainedconsonantsvs.

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unconstrainedconsonantswithsessions2and3.Importantly,thiseffectdoesnotemerge

foranyothercondition,providingsomelimitedevidenceforgreateradaptationinthe

Differentcondition.

Table3.6.Differentcondition;session1excluded;[m]-[n]switchesexcluded.


Constraint 0.73* 0.35 4.76 0.03

RandomEffects


0.81

Finally,abetween-conditionanalysiswasperformedonthedataexcluding[m]-[n]

swaps.Inamodelthatincludedallsessions,thecriticalthree-wayinteractionbetween

condition,constraint,andsessionwasnotsignificant(seeTable3.7).Inamodelthatonly

includedsessions2and3,thecriticaltwo-wayinteractionwasalsonotsignificant(see

Table3.8),differingfromtheeffectfoundwhen[m]and[n]wereincludedintheanalysis.

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Table3.7.Betweenconditioncomparison;allsessions;[m]-[n]switchesexcluded.


Constraint 0.32* 0.14 5.48 0.02Session 0.01 0.13 0.01 0.92Condition -0.19 0.19 0.99 0.32Constraint:Session -0.08 0.26 0.09 0.76Constraint:Condition 0.37 0.38 0.95 0.33Session:Condition 0.49 0.38 1.61 0.2Constraint:Session:Condition 0.81 0.76 1.12 0.29

RandomEffects


0.31

Table3.8.Betweenconditioncomparison;session1excluded;[m]-[n]switchesexcluded.


Constraint 0.23 0.19 1.55 0.21Condition 0.05 0.26 0.04 0.85Constraint:Condition 0.88 0.52 2.93 0.09

RandomEffects


0.29

Thepost-testquestionsrevealedthatparticipantsgenerallyhadlittleexplicit

knowledgeaboutthedesignoftheexperiment.Noparticipantsindicatedtheywereaware

ofthephonotacticconstraintsbasedontalker/vowel.Only2participants,ofthe10who

wereexposedtoatleastonenon-nativetalker,wereabletodetectthattheyhadhearda

non-nativetalker.Ofthese,oneheardthenon-nativetalkerasbeinganativespeakerofan

EastAsianlanguage,whiletheotherheardthenon-nativetalkerasbeinganativespeaker

ofVietnamese.It’sunclearwhetherexplicitdetectionofmodeltalker’snon-nativelanguage

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backgroundisnecessarytosuccessfullyadaptintheDifferentcondition.(Notethat

previoustonguetwisterexperimentshaveshownthatexplicitknowledgeofthe

experimentaldesignhavemadelittledifferentinparticipantbehavior;e.g.,Dell,etal.

2000.)

Tosummarize,wefoundinconsistentevidenceforourinitialpredictions.Two

significantresults,bothfollowingfrompost-hocanalyses,supportingthehypothesiswere

found:first,thatwhen[m]-[n]swapswereincluded,participantsshowedahighersyllable

maintenanceeffectinlatersessionsoftheDifferentconditionthaninthelatersessionsof

theSharedconditions.Andsecond,thatwhen[m]-[n]swapswerenotincluded,

constrainedconsonantsmaintainedtheirpositionmorefrequentlythanunconstrained

consonantswithinthelatersessionsoftheDifferentcondition(andnotinanyother

condition).Overall,however,theseeffectswerequitebrittle,andchangeddependingon

whichsessionswereincludedintheanalysisandwhetherornot[m]-[n]swapswere

included.Moreover,wesurprisinglydidnotfindsignificantresultofadaptationinthe

baselineVowelcondition,whichmakesitdifficulttocontextualizetheresultsinother

contiditions.

3.4.1. Discussion

Inthecurrentstudy,participantswereexposedtonovel,non-nativephonotactic

constraintscontingentonmodeltalkerinatonguetwisterparadigm,withthelanguage

backgroundofmodeltalkersmodulatedacrossconditions.Theresultswereultimately

inconclusive,withsomeweakevidencepointingtowardsparticipantsacquiringthe

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constraintswhenmodeltalkersdifferedintheirlanguagebackground,butnotwhenthey

sharedalanguagebackground.Inaddition,weunexpectedlydidnotreplicatethewell-

establishedadaptationeffectsfromprevioustonguetwisterstudiesintheVowelcondition,

whichmakescontextualizingresultsfromotherconditionsdifficult.Finally,theoverall

syllablemaintenanceeffectforconstrainedconsonantswassurprisinglylowduetoalarge

numberof[m]-[n]swaps,whichfurtherobscuredanycomparisonsbetweenconditions.

Whatisbehindthehighnumberof[m]-[n]swaps?Giventhatmultipleprevious

studieshaveusedtheseconsonantswithoutsuchcomplications,it’slikelythatthe

differenceinthemethodologyofthecurrentstudy—inwhichparticipantslistentothe

tonguetwisterbeforeproducingit—contributedtotheabnormallyhighnumberofswaps.

Onepossibility,giventhatthistaskinvolvedperception,isthehighperceptual

confusabilityof[m]and[n]:listenersfrequentlymisidentify[m]as[n],andvice-versa,in

speechinnoise(e.g.,MillerandNicely,1955;PhatakandAllen,2007).It’spossiblethatthe

similarityof[m]and[n]inperceptionresultedindown-streamerrorsinproduction.While

otherconsonantsincludedintheexperimentarealsoperceptuallyconfusable(e.g.,[p]and

[k];seeTable3.3),swapsbetweenunconstrainedconsonantswerenot,bydefinition,

alwaysillegal,andthuswouldnothaveaffectedsyllablemaintenanceratesinthesame

way.

Anothercontributingfactormayhavebeenthecoder’sperceptionofparticipants’

[m]and[n]productions.Ifthecoderhadanatypical[m]-[n]categoryboundary,inwhich

oneperceptualcategorywaswideandtheotherwasfairlynarrow,itcouldhaveresultedin

frequentmiscategorizations.Specifically,wewouldexpectthecodertoconsistentlychoose

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onenasalovertheother.Indeed,therewere231total[n]errorsfor[m]targets,andonly

119[m]errorsfor[n]targets(Miller&Nicely,1955,findasimilarasymmetryin

perception).Thiswasfairlyconsistentacrosscoders,however,suggestingit’slikelynot

relatedtoonecoder’sidiosyncraticperceptualcategoryboundary.

Smalleetal.,(2017)—theonlyotherstudytouseasimilarparadigm—didnotfind

depressedsyllablemaintenanceeffectsforconstrainedsyllables.Instead,theauthorsfound

asurprisinglyhighsyllable-positioneffectforunconstrainedsyllables(87.4%,roughly

12%higherthanpreviousstudies),whichwasnotreplicatedinthisstudy.Therewerea

numberofimportantdifferencesbetweenthecurrentstudyandSmalleetal.,(2017)that

mighthaveresultedinthedivergentfindings(differentsetofconsonantsandvowels;

Dutchparticipants/twisters,ratherthanEnglish;4sessions;etc.)

AnotherperplexingfindingwasthelackofaneffectintheVowelcondition.When

[m]-[n]swapsareremoved,thesyllablepositioneffectdoesreach100%forconstrained

consonantsinthethirdsession,whichisinlinewithpreviousresults.Thisisoveronly13

errors,however,whichisfartoosmallasampletodrawdefinitiveconclusionsfrom.This

smallsamplesizemayhaveresultedinthelackofaneffect—evenwith[m]-[n]swaps

included,the629errorswouldbethesecondsmallestnumberreportedforanyprevious

tonguetwisterexperimentusing2nd-orderconstraintsconditionedonvowels(see

AppendixF).ThiswasinlargepartduetotheverylowerrorrateintheVowelcondition

(2.3%)—lowerthananypreviousexperimentwith2nd-orderconstraintsexceptSmalleet

al.,(2017).Giventhattheerrorratefortheexperimentasawholewasinlinewith

previouswork,thelowerrorrateintheVowelconditionwasmostlikelycausedbythe

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smallnumberofparticipants,andlargevariancebetweenparticipanterrorrate:thetwo

participantswiththelowesterrorrates,bothlessthan1%,wereintheVowelcondition.A

relatedproblemwasthatanotherparticipantintheVowelconditionhadthesecondhighest

errorrate.Whilethisincreasedthesizeofthesample,62%oftheerrorsfortheVowel

conditioncamefromasingleparticipant,whichisclearlynotarepresentativesample.

AsecondpossibleissuewiththeVowelconditionwasthephoneticsimilarityofthe

vowels—[ɪ]and[ɛ]aremuchmoresimilarthan[ɪ]and[æ],thevowelsusuallychosenin

previoustonguetwisterparadigms.Inthepost-experimentquestionnaire,oneparticipant

mentionedtheycouldnotconsistentlytellthemodeltalker’svowelproductionsapart,

whiletwootherssometimesheardthemodeltalkers’[ɛ]vowelas[ɪ].Giventhatthe

phonologicalfeaturesoftheconsonantsinvolvedina1st-orderconstraintaffectserrorsin

tonguetwisters(Goldrick,2004),itmayalsobethecasethatthesimilarityofthe

conditioningvowelsina2nd-orderconstraintcanweakenthesyllable-positioneffect.

Infuturefollow-upexperimentsusingasimilardesign,anumberofstepscanbe

takentoavoidsomeoftheissueshighlightedabove.Mostobviously,alargernumberof

participantsisrequiredforamorerepresentativesample.Thatsaid,therearesome

logisticalobstaclestoincreasingthenumberofparticipants:becausetherecordingsneed

tobecodedforerrorsbyhand,itisahighlytimeandmoney-intensiveparadigm.One

strategytomitigatethiscostistoshortenthelengthoftheexperiment.Asinprevious

tonguetwisterexperiments,thenumberoferrorsdecreasesoverthecourseofthe

experiment,bothwithineachsessionandacrosssessions—roughlyhalfofallerrors

occurredinthefirstsessionalone—resultingindiminishingreturns.Shorteningthelength

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oftheexperimentto96trialspersessionandreducingthenumberofsessionsto2,while

increasingthenumberofparticipants,willresultinmoreefficientspeecherrorcoding,due

totheincreaseddensityoferrors.Second,afollow-upstudyshoulduselessperceptually

confusableexperimentallyconstrainedconsonants.Whilemostpreviousstudieshaveused

phoneticallysimilarconsonants(e.g.,[k]-[g],[m]-[n],[f]-[s]),thereisnoapriorireasonfor

this.Movingawayfromsuchpairsshouldmitigatethepossibleinteractionbetweenthe

auditorypresentationofthetwistersandthephoneticsimilarityofconstrainedsegments,

resultinginfewerillegalswitchesbetweenexperimentallyconstrainedconsonants.

It’spossibleadifferentdesignmaybebettersuitedtoinvestigatethequestionat

hand.Onealternativeisamodificationoftheconstraint-switchingdesignemployedin

Andersonetal.(2019).Inthefirstexperimentalblock,participantswereexposedtoa1st-

orderconstraintinatonguetwisterexperiment.Thisconstraintwasthenreversedinthe

secondblock(e.g.,if[f]wasconstrainedtoonsetinBlock1,itwasconstrainedtocodain

Block2),thenreversedagaininthethirdblock.Andersonandcolleaguesfoundslower

adaptationforthereversaloftheconstraint,suggestinganincrementalphonotactic

learningmechanism.Undertheframeworkpresentedinthisstudy,however,participants

werelearningandthenunlearningthesamelaboratory“mini-grammar”inallblocks.Ina

modifiedversionofthestudy,twisterscouldbepresentedauditorily,withthemodel

talkersswitchingtheirlanguagebackgroundsbetweenblocks(seeWeissetal.,2009,fora

similardesigninastatisticallearningparadigm).Thismayserveasacuetolearnersthat

theyareinfactbeingexposedtodifferentlanguagesineachblock,spurringfaster

adaptation,encouragingthemtoseparatetheevidencefortheconflictingconstraintsinto

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different“mini-grammars”.Inaddition,thisparadigmonlyrequiresasinglesession,

allowingfortherecruitmentofagreaternumberofparticipants.

3.4.2. Production-perceptiondynamicsandphonotacticadaptation

Recentresearchexploringtherelationshipbetweenspeechproductionandspeech

perceptionhasplacedalargeemphasisontheroleofprediction(e.g.,DellandChang,2014;

PickeringandGarrod,2007;PickeringandGarrod,2013).PickeringandGarrod(2007)

proposethatwhentheperceptualsystemmakespredictions—aubiquitousprocessin

comprehensionthatoccursatmultiplelevelsofrepresentation—itrecruitstheproduction

systemtoconstructaforwardmodelthatanticipatesupcominglinguisticinput.The

discrepancies,orerror,betweentheforwardmodel’spredictionsandtheobservedinput

drivefutureadaptation.Underthisframework,phoneticimitationisaresultofcovert

imitationduringperception,duringwhichspeakersrecruittheproductionsystemto

predicttheirinterlocutor’sspeech.Thisinturnbringsthespeaker’sproductionsystem

moreinlinewiththeirinterlocutor’s,resultinginphoneticimitation.

KittredgeandDell(2016)investigatedtransferofphonotacticconstraintslearnedin

perceptiontothoselearnedinproduction.Participantsalternatedproducingtongue

twistersandhearingstringsofsyllablesthatconflictedintheirphonotacticconstraints.

Critically,constraintsparticipantswereexposedtoinperceptiononlyinterferedwith

constraintsinproductionwhentheperceptiontaskinvolvedimitation,eitherbywayof

silentproductionorerrormonitoringwithoutorthographicsupport(seealsoWarkeretal.,

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2009).

Inthecurrentstudy,participantsshadowedthemodeltalker’sspeech.Under

PickeringandGarrod’sframework,ifthisshadowinginvolvescovertimitation,and

thereforeprediction,itshouldhaverecruitedtheproductionsystem.Whiletheresultsof

thecurrentexperimentaresomewhatinconclusive,it’spossiblethislinkbetween

perceptionandproductionisacriticalpathwaytopassinformationaboutcausal

inferences—inthiscasetherelationshipbetweenphonotacticvariationandthemodel

speakers’backgrounds—fromtheperceptionsystemtotheproductionsystem.It’spossible

thatwhiletheproductionsysteminisolationisrelativelyinsensitivetothecausalstructure

underlyingphonotacticvariation(e.g.,Andersonetal.,2019),whenitisco-activewiththe

perceptionsystem,itgainsaccesstosuchcausalinferences.Theinconclusivecurrent

resultsdonotprovideevidenceforthisaccount,however,andfollow-upstudiesarecritical

tofurtherexplorethispossibility.

3.5. Conclusion

Inthecurrentstudy,weinvestigatedtheroleofcausalinferenceinphonotactic

adaptationinatonguetwisterparadigm.Wepositedthatspeakerswouldusetheirprior

experiencewithphonotacticvariation—thatitvariestoalargedegreebetweenlanguages,

andverylittlebetweenspeakersofthesamelanguagevariety—toguidetheiradaptationto

novelconstraints.Weexposedparticipantsto2nd-orderphonotacticconstraints

conditionedonmodeltalker,whilemodulatingthelanguagebackgroundsofthemodel

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talkers.Wepredictedthatparticipantswouldadapttoagreaterdegreewhentalkers

differedintheirlanguagebackgrounds,astheywouldconstructaseparatephonotactic

grammarforeachtalker(i.e.,theywoulddetecttheywerelearningtwoseparate

“laboratorylanguages”).Theresultswereultimatelyinconclusive,althoughsomeevidence

wasfoundinthepredicteddirection.Totheextenttheseeffectsarereliable,itsuggests

thatparticipantsmayusethelanguagebackgroundofthemodeltalkersasacuetoa

changeinphonotacticcontextbetweenmodeltalkers.Iftheseeffectswereconfirmedin

futurestudies,itwouldsuggestthatspeechproductionismoresensitivetosuchhigh-level

causalinferencesthanrecentevidencehassuggested,especiallyinferencesinvolvingthe

languagebackgroundsoftalkers.

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4. Conclusion

Inthisdissertation,weexploredthewaysinwhichthestructureofphonotactic

variationthatspeakersexperiencecaninduceadaptationtonovelconstraintsinsome

contexts,anddampenitinothers.Westartfromtheassumptionthatadaptation,across

domains,ismotivatedbypriorexperience.Thisisacomputationallevelaccountof

phonotacticadaptation(Marr,1982):whilepreviousworkhasfocusedonthemechanisms

involvedinphonotacticadaptation(e.g.,Warker&Dell,2006),thisdissertationexamines

whyweadaptinthefirstplace,andunderwhatcircumstances.Thislineofinquiryhas

previouslybeeninvestigatedinthedomainofphonetics(Kraljic,Samuel,&Brennan,2008;

Liu&Jaeger,2018),inwhichlistenersadapttovariationwhentheyhaveevidenceitis

systematicandrelevantforagiventask(i.e.,differencesbetweenindividualtalkersare

relevantforrecognizingspeechsounds)butdonotadaptwhentheyhaveevidencethe

variationisincidentalforagiventask(i.e.,disruptionsfromapeninthemouthofatalker

arenotrelevantforrecognizingspeechsoundsinothercontexts).Thispatternof

adaptationsuggeststhatlistenersmustproperlyattributevariationtoitsunderlying

sourceforthegiventaskwhenadapting.Inthecaseofphonetics,listenersmakecausal

inferencesaboutthesourcesofvariationbasedonthehighdegreeofvariationendemicto

thephoneticsofindividualtalkers,acontributingfactortotheclassic“lackofinvariance”

problem.

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Thestructureofphonotacticvariationismarkedlydifferentfromthatofphonetic

variation:individualtalkersarelikelytohavesimilarphonotacticgrammars,whiletalkers

ofdifferentlanguagesarelikelytohavedistinctgrammars.Assuch,wearguedthat

phonotacticadaptationwouldbehavedifferentlyfromphoneticadaptation.Wepredicted

speakerswouldadapttodistinctphonotacticgrammarsfordifferenttalkerstoagreater

degreewhenthosetalkersdifferedintheirlanguagebackgroundthanwhentheyshareda

languagebackground.Ineachexperimentreportedinthedissertation,thispredictionwas

testedbyexposingparticipantstotwotalkersexhibitingdifferentphonotacticconstraints

(i.e.,2nd-orderconstraintsconditionedontalkeridentity),whilemodulatingthelanguage

backgroundofeachtalker.Weexploredadaptationinbothperception(Study1)and

production(Study2);herewesummarizetheresultsofeachstudy,considertheir

implicationsfortheoriesofadaptation,andpositfuturedirectionsforthislineofresearch.

4.1. Study1

InStudy1,wetestedadaptationinarecognitionmemoryparadigm,exposing

English-speakinglistenerstononsensesyllablesthatreflecteddifferenttalker-dependent

phonotacticconstraints(e.g.,forTalkerA,stopsareconstrainedtoonsetandfricativesto

coda;forTalkerB,viceversa).Crucially,talkerseithersharedalanguagebackground(two

FrenchortwoEnglishtalkers),ordifferedintheirlanguagebackgrounds(oneEnglish,one

Frenchtalker).InExperiment1A,wealsomodulatedthestrengthofthecuetothenon-

nativespeakers’languagebackgrounds,withmoreorlessnativeEnglish-likevowels([u]

vs.[y]).

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Experiment1ArevealedalowdegreeofadaptationfortheNativeSharedcondition,

andamoderatedegreeofadaptationforeveryothercondition.Thisresultlargely

supportedourhypothesis,withagreaterdegreeoflearningfortheDifferentconditions

thantheNativeSharedconditions.Therewere,however,aspectsoftheresultsthatwere

unexpected:first,adaptationoccurredineachcondition,eventhoseinwhichbothtalkers

sharedalanguagebackground.Ouroriginalpredictionwasthatnoadaptationshouldoccur

insuchacontext,asthesharednativebackgroundsofthetwotalkersshouldblock

adaptation.Itappearsthatthestrengthofthebottom-upevidenceoftalker-specific

phonotacticconstraints,however,overcamelisteners’top-downinferencesaboutthe

sourceofthevariation—but,critically,adaptationwasstilllowerthaninotherconditions.

Asecondunexpectedresultwasthatthestrengthofthecuetolanguagebackgrounddid

notappeartoaffectadaptation.Wearguedthattheweakcuewassufficientforlistenersto

determinethenon-nativestatusofthetalker,makingfurthercuesredundant.

Athirdunexpectedresult,andthemosttroublingforthehypothesis,wasthesimilar

degreeofadaptationfortheDifferentconditionsandtheNon-NativeSharedconditions.We

suspectedthissurprisinglyhighdegreeofadaptationfortheNon-NativeSharedcondition

wasaresultofthetwoFrenchtalkerssoundingdissimilar,duetoonetalker’ssomewhat

aberrantproductions.Assuch,inExperiment1Bwerecordedanoveltalker,andre-ran

threeofthefourconditionsof1A(wedidnotincludetheNativeSharedcondition).

Theresultsofthisfollow-upexperimentstrengthenedtheevidenceforour

hypothesis,astheDifferentconditionsshowedahighdegreeofadaptation,andtheNon-

NativeSharedconditionshowedonlyamoderatedegreeofadaptation.Butthisresultalso

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hadtwosomewhatsurprisingaspects:first,whydidadaptationincreaseintheDifferent

conditions?Itappearsthatparticipantsspecificallydidnotstronglyadapttoaberrant

talker’sphonotacticconstraintsinExperiment1A,regardlessofcondition.Assuch,

replacingthattalkerresultedinanoverallboosttoadaptationintheDifferentconditions.A

secondsurprisewasthatadaptationdidnotdecreaseintheNon-NativeSharedcondition.

Wearguedthatthemoderatedegreeofadaptationinthisconditionwasaresultof

listeners’asymmetricknowledgeofnativevs.non-nativelanguages.Whenlistenersare

exposedtotwotalkersofalanguagetheyarehighlyfamiliarwith,theyarelikelymore

confidentthesetalkerssharealanguagebackgroundthanwhenexposedtotalkersofaless

familiarlanguage.Assuch,theymaybemorelikelytoinferthenon-nativetalkersdon’t

sharealanguagebackground,andadapttoamoderatedegree.

Asawhole,theresultsofExperiment1suggestedthatlistenersadaptedtoagreater

degreewhentalkersdifferedintheirlanguagebackground.Moreover,itsuggested

listenershaveastructuredmodelofphonotactics,assigningdistinctphonotacticgrammars

tonativevs.non-nativelanguages.Itremainedunclear,however,whetherlistenerswere

capableofassigningdistinctphonotacticgrammarstodifferentnon-nativelanguages.In

Experiment2,weaddressedthisquestionbyexposinglistenerstotwonon-nativespeakers

ofdifferentlanguages(HindiandHungarian).Wepositedthatiflistenersmadedistinctions

betweennon-nativelanguages,theywouldtreatanylanguagedifferencesasrelevant

variation,andthereforeadapttoahighdegreeinthiscondition.If,ontheotherhand,

listenerssimplygroupedallnon-nativetalkerstogether,theywouldonlyadapttoa

moderatedegree.Inaddition,weincludedtwoconditionsfromExperiment1:theMixed

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Differentcondition(i.e.,onenativeandonenon-nativespeaker)andtheNon-NativeShared

condition.

Resultssupportedthewithinnon-nativedistinctionshypothesis:listenersadapted

toahighdegreeofadaptationwhentalkersdifferedintheirlanguagebackgrounds,even

whenbothtalkerswerenon-native.Theseresultssuggestthatthecriticaldistinction

listenersusewhenpositingdifferentphonotacticgrammarsfordifferentspeakersis

languagedifference,ratherthanthemorespecificdistinctionofnativevs.non-native.

Additionally,theNon-NativeSharedconditionreplicatedExperiment1Bwithadifferent

stimulusdesign,languages,talkers,andnumberofitems,showingamoderatedegreeof

adaptation.

Study1shedslightonthemotivationforphonotacticadaptation.Patternsof

adaptationreflectthetypeofphonotacticvariationlistenersexperiencefromvarious

sourcesintheirdailylives,suchasaccentedEnglishspeechorexposuretonon-native

languages.TheseresultsalsosuggestthatphonotacticadaptationisheightenedinL2

contexts(seeWarker,2013),andmaybeakeypartoftheearlystagesofL2acquisition.

Learnersarefacedwithprofoundlydifficultproblems,suchasdiscoveringword

boundaries,atthebeginningofL2acquisition.Rapidphonotacticadaptationinperception,

particularlytosubsetphonotactics,mayserveasafastandefficientadjustmentthatallows

leanerstobettersegmentwords,aspreviousworksuggeststhatphonotacticcuesinthe

inputareusefulforsegmentation(e.g.,Brent&Cartwright,1996)andthatadultsusethese

cuestoguidesegmentation(e.g.,McQueen,1998).AdaptingtoL2subsetphonotacticsmay

allowlearnerstoquicklynarrowthesetofpossibleword-formstheyhavetoconsider

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duringcomprehension,aidingsegmentationandlexicalaccess.Suchquickadjustmentsto

L2speecharelikelynotavailableforotherphonologicalstructuresthatareheavily

influencedbylow-levelperceptualprocesses.L2supersetphonotactics(e.g.,consonant

clustersnotpresentintheL1),forexample,areverydifficulttolearn(e.g.,Parlato,

Christophe,Hirose,&Dupoux,2010),whichmayreflectinpartperceptualinterference

fromlisteners’L1s(e.g.,Dupoux,etal.,1999).Phonotacticadaptation’sroleinL2

acquisitionisaripeavenueforfutureresearch(seefuturedirectionssectionbelow).

4.2. Study2

InStudy2,weexaminedwhethertheprinciplesofadaptationwetestedin

perception—thatlearnersmakeinferencesaboutthecauseofvariationbasedontheir

priorexperience,andtheseinferencesguideadaptation—alsoholdinspeechproduction,

usingamodifiedtonguetwisterparadigminwhichparticipantsrepeataftermodeltalkers.

Evidencefromprevioustonguetwisterexperimentssuggestedthatspeakersbuiltseparate

phonotacticgrammarsinlaboratorycontexts,andwereabletoseparateevidencefor

constraintsinthelaboratorygrammarfromthoseusedintheirnativelanguage(Warker,

2013).AsinperceptioninStudy1,wearguedthatspeakerswererecruitingtheirL2

acquisitionfacultiesinadaptation.IfadaptationisdrivenbyL2acquisition,thenitfollows

thatlearnersshouldbesensitivetocuesregardingthelanguagebackgroundofthemodel

talkerstheyarerepeatingafter.Thelanguagebackgroundoflistenersmayserveascuefor

learnerstodetectachangeincontext,andseparatetheevidenceforconflictingphonotactic

constraintsintoseparategrammars(e.g.,Weiss,etal.,2009).However,anumberofrecent

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studieshavesuggestedthatphonotacticadaptationinproductionisresistanttotop-down

inferences(e.g.,Andersonetal.,2019),suggestingthatlearnerswillbeunabletoseparate

evidencefortheconflictingphonotacticconstraintsbasedontalkerlanguagebackground.

MirroringthedesignfromStudy1,participantswereexposedtomodeltalkerswho

sharedanativelanguagebackground(2Englishtalkers),anon-nativelanguage

background(2Germantalkers),ordifferedintheirlanguagebackgrounds(1English,1

Germantalker),witha2nd-orderphonotacticconstraintconditionedontalkeridentity.A

controlconditionwasincludedinwhichthephonotacticconstraintwasconditionedonthe

identityofthevowel,followingprevioustonguetwisterstudies(e.g.,Warker&Dell,2006).

WepredictedahighdegreeoflearningintheDifferentandVowelconditions,andalow-to-

moderatedegreeoflearninginthetwoSharedconditions.

Theresultswereultimatelyinconclusive.Whiletherewassomeevidenceofahigher

degreeoflearningintheDifferentcondition,theeffectwasbrittle,andwasnotconsistent

amongdifferentanalyses.Surprisingly,wefoundnoeffectoflearninginthecontrol

condition,possiblyduetoasmallnumberoferrors,amajorityofwhichcamefromasingle

participant.Therewasalsoanoverwhelmingeffectofphoneticsimilarityforthetarget

consonants([m]and[n])inallconditions,resultinginahighnumberof[m]-[n]swaps.Due

tothedesignoftheexperiment,theseswaps,bydefinition,violatedthephonotactic

constraint,resultinginsurprisinglylowoverallmaintenanceofsyllablepositionforthe

experimentallyconstrainedconsonants.Thismayhavebeenduetothemodifieddesign,in

whichparticipantsheardthetwistersbeforerepeatingthem:theperceptualsimilarityof

nasalconsonantsmayhaveinterferedwiththeensuingproduction.

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4.3. FutureDirections

Themostobviousfollow-uptobothStudies1and2arereplications.InStudy1,

replicationsshouldincludeagreaternumberoftalkers,aslistenersappearedsensitiveto

fine-grainedphoneticdifferencesbetweentalkers(seedifferencesbetweenExperiments

1Aand1B).InStudy2,replicationsshouldincludeagreaternumberofparticipants,witha

designmodifiedinanumberofways(lessphoneticallysimilarvowelsinVowelcondition;

lesssimilarexperimentallyconstrainedconsonants;etc.).AnalternatedesignforStudy2

wouldexposelistenerstoa1st-orderconstraintinaninitialblock,followedbyareversalin

thefollowingblock,withmodeltalkeridentitychangingineachblock(Anderson,etal.,

2019).Whilepreviousstudieshaveshownreducedlearningforthereversedconstraint,if

speakersaresensitivetolanguagebackgroundinadaptationinproductiontheymaydetect

acontextchangefromoneblocktotheother,andadapttoanequaldegreeafterthe

reversal.

WehypothesizedthatlearnersarerecruitingtheirL2acquisitionfacultiesin

phonotacticadaptation,andtreatingthelaboratoryexposureasanovellanguage.

Accordingtoouraccount,thismotivatesadaptation,aslearnersareabletoseparatetheir

experiencewiththeirnativelanguagefromthenovelexperimentalinput,andtherefore

rapidlyadapttonovelconstraints.Iflearnersbelievetheyarebeingexposedtospeech

fromtheirnativelanguage,however,theyshouldbelesslikelytoadapt,astheyhave

extremelystrongpriorsabouttheirnativelanguagephonotacticconstraintsfromalifetime

ofexperience.Wepredictthatminutesoflaboratoryexposureinthelearner’sL1willnot

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beenoughtoovercomethesepriors.Onewaytotestthispredictionwouldbetoexpose

learnerstorealwordsintheirnativelanguage,presentedinsemanticallymeaningful

contexts.Forexample,atonguetwistermadeupofrealwords(e.g.,pothamkingfin)could

beinitiallypresentedtoparticipantsaspictures,beforeorthographicsupportappears(just

astwisterswereinitiallypresentedauditorilyinStudy2).Ifrapidphonotacticadaptationis

partoftheprocessofL2acquisitionwewouldnotexpectittobeactiveinnativespeech

contexts;subsequently,wewouldpredictlowratesofadaptationinsuchcases.

IfphonotacticadaptationisindeedtiedtoL2acquisition,wemightalsoexpectthat

participants’performanceinthesetasksmaypredictoutcomesforlongertermL2learning.

Forexample,ifrapidphonotacticadaptationisoneofthekeystounlockingword

segmentationearlyinL2acquisition,participantswhoadapttoagreaterdegree,andare

thereforecapableofquicklylearningcuestonovelwordboundaries,mayshowgreater

abilitytosegmentwordsintheirL2afterexposure.Astudyalongtheselinescouldgive

participantsapre-testusingthemethodsinStudy1beforeanL2immersionprogram,

followedbyapost-testwordsegmentationtask(e.g.,McQueen,1998).

Anotherquestionthatarisesfromthisresearchishowpresentingexplicit

informationabouttalkerswouldaffectparticipantbehavior.Inspeechperceptionresearch,

modifyinglistenerexpectationsabouttalkercharacteristicssuchasdialect,eveninsubtle

ways,canhaveimportantconsequencesforspeechperception(e.g.,Hay&Drager,2010).

Evenmanipulatingthenumberofspeakersthatlistenersexpecttohearcanaffect

processingofthesamelinguisticinput(MagnusonandNusbaum,2007).Inthecurrent

studies,wehypothesizedthatadaptationisinducedbythelearner’sbeliefthattheyare

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beingexposedtodifferentlanguages.Thisbeliefabouttalkers’languagebackgrounds

comesfromphoneticsalone,asparticipantsaregivennoexplicitinformationaboutthe

experimentaltalkerswhatsoever.Ifwepresentedexplicitinformationthatspeakers

differedintheirlanguagebackgrounds(e.g.,“BarbaragrewupspeakingEnglishinOhio,

whileBélagrewupspeakingHungarianinBudapest”)wemightexpectittostrengthen

participants’confidencethatthetalkersdonotsharealanguagebackground,andthus

boostadaptation.Alternatively,presentingexplicitinformationthattalkerssharea

languagebackgroundmaydampenadaptation.

Insomeconditions,itmaybethecasethatlistenersarealreadyfullyconfidentin

theirbeliefsabouttalkers’languagebackgrounds,suggestingthattheirconfidencecould

notbeincreasedfurtherbytop-downinformation.IntheDifferentconditioninStudy1,for

example,listenersmayhavealreadybeenfullyconfidentthattalkersdifferedinthose

cases,asmodulatingthe“non-nativeness”ofthephoneticvowelcuesintheStrongvs.

WeakDifferentconditionsdidnotchangethedegreeofadaptation.Inthiscase,explicit

informationthattalkersdifferedintheirlanguagebackgroundsmaynotaffectadaptation.

Informationthattalkerssharealanguagebackground,however,maydecreaseadaptation.

IntheSharedconditions,listenersappearedtoshowvaryingdegreesofconfidenceabout

thelanguagebackgroundsoftalkers.WemightexpectintheNon-NativeSharedconditions,

forexample,thatiflistenersareexplicitlytoldthetwospeakerssharealanguage

background,thedegreeofadaptationmightdecrease.Inthissamecontext,pushing

participantsinthereversedirection,bygivingtheminformationthatthetwotalkersdiffer

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intheirlanguagebackgrounds,mightoverridethephoneticsimilaritiesofthetwotalkers

andincreaseadaptation.

Anothernaturalextensionofthisdissertation,givenourfindingsthatlearnersadapt

toagreaterdegreewhentalkersdifferintheirlanguagebackgrounds,iswhetherlearners

wouldalsoshowincreasedadaptationtotalkersofdifferentdialectsofthesamelanguage

(e.g.,tworegionaldialectsoftheUnitedStates).Theexactnatureoflistener’sprior

experiencewithdialectsandphonotacticvariationisnotentirelyclear.Ifdialectsvaryin

theirphonotactics,buttoalesserextentthanlanguagesvary,wewouldpredictlisteners

wouldadapttoamoderatedegreetotalkersofdifferentdialects.Whiledialectsalmost

certainlyhavelesspervasivevariationincategoricalconstraints(e.g.,there’snodialectof

Englishthatallows[ŋ]inonsetposition),theymayshowmorevariationforgradient

phonotacticconstraints(e.g.,[s]appearsmoreofteninonsetthan[z]).

Whilequantifyingphonotacticvariationisakeychallengeforfuturework,itis

unclearhowtooperationalizeandcomparedistancebetweenphonotacticgrammars.

Whileweareconfidentthatlanguagesdiffertoagreaterdegreethanindividualtalkers,

thereisnostraightforwardmethodtodrawingeitherquantitativeorqualitative

distinctionsbetweenpairsoflanguagesforanumberofreasons.First,itmaybethecase

thatnotallphonotacticdifferencesarecreatedequal.Differencesthathaveawiderimpact

onthelexiconofalanguage,suchasconstraintsontheshapeofsyllables(e.g.,languages

limitedtoonlyCVsyllablesvs.languagesthatallowmorecomplexsyllables)shouldbe

weightedmoreheavilythandifferenceswithregardstosinglesounds(e.g.,languagesthat

allow[ŋ]inonsetvs.thosethatdonot).Second,itisunclearhowtocomparelanguagewith

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widelydifferentsoundinventories.Unlike,forexample,Cantonese,Englishdoesnothave

phonotacticconstraintsonlexicaltone,butofcourselexicaltoneisnotafeatureofEnglish

atall.Finally,itisunclearifphonotacticdistanceshouldbequantifiedinan“objective”

way,orifdistanceshouldbemeasuredbyhowdetectablephonotacticdifferencesare

betweenlanguagesfromthespeaker’spointofview.Thisperceiveddistancemaybethe

mostimportantaspectforthepurposesofadaptation.

Finally,wecouldaskwhatotherdomainsthislinkbetweentalkerlanguage

backgroundandunderlyinggrammarextendto.Speakersexperiencevariationatevery

leveloflinguisticrepresentation.Manyofthesedomainsmayholdasimilarstructurein

variationtophonotactics—ahighdegreeofvariationbetweentalkersofdifferentlanguage

varieties,andalowdegreeofvariationbetweentalkersofthesamelanguagevariety.As

such,wewouldexpectthesameprinciplesofcausalinferencetoapply.Forexample,this

inferencemayextendtolearningofnovelorunlikelysyntacticormorphologicalstructures.

Inthecaseofartificiallanguageparadigms(e.g.,Schumacher,Pierrehumbert,&Lashell,

2014),ifstimuliarepresentedbynon-nativetalkers,itmayboostadaptation.For

adaptationinnativelanguagecontexts(e.g.,Jaeger&Snider,2013),ifstimuliarepresented

bytalkersofdifferentdialectsitmayalsoincreaseadaptation,assyntaxmayvarytoa

greaterdegreebetweenspeakersofdifferentdialects(e.g.,Labov,1969)thanitdoes

betweenindividualswithinaspeechcommunity.

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4.4. Conclusions

Intwostudies,wehaveinvestigatedthewaysinwhichspeakers’priorexperience

guidesphonotacticadaptation.Wehypothesizedthatspeakersadapttorelevantor

systematicvariation,whileignoringirrelevantorincidentalvariationforthetaskathand,

basedontheirpreviousexposuretophonotacticvariation.Wefoundstrongevidencefor

thiseffectinperception,butonlyweak/inconclusiveevidenceinproduction.Thisevidence

extendstheoriesofadaptationinwhichspeakersmakeinferencesaboutthecausesof

variationtoanoveldomain.Inaddition,wereframethephenomenonofphonotactic

learningasapartoftheL2acquisitionfaculty.Asawhole,thisdissertationexploreshow

speakerscontendwithandadapttoendemicvariation,sheddinglightonthemechanisms

andmotivationsforadaptation.

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5. Appendix

5.1. AppendixA–Study1vowelacousticsanalysis

ResultsfromExperiments1Aand1BfoundnodifferencebetweenWeakandStrong

Differentconditions,whichweredifferentiatedbyeitherarelativelyweakphoneticcueto

theFrenchtalkers’non-nativelanguagebackground(useoftheFrenchvowel[u])ora

strongercue(useoftheFrenchvowel[y]).Oneexplanationforthislackofeffectisthatthe

Weakconditionincludedasufficientnumberofacousticcuessuchthatlistenerscould

confidentlyinferthattheFrenchtalkerswerenon-native.Analternative,however,isthat

theFrenchtalkers’productionsof[u]and[y]werenotsufficientlyacousticallydistinct,and

thereforethevowelmanipulationmadelittledifferencetolisteners.Toinvestigatethis

possibility,apost-hocacousticanalysiswascompletedoftheFrenchspeakers’vowel

productionsinExperiments1Aand1B.

Vowelsintervalsforeachitemwerehand-markedinPraat.F1andF2valueswere

thenautomaticallymeasuredatthemid-pointofeachvowelusingascript.Atotalof324

vowelsweremeasured(108foreachoftheFrenchtalkers).NotethatdifferentLPC(linear

predictivecoding)settingswereusedtoaccuratecapturemaleandfemaleformantvalues.

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Figure5.1.ScatterplotofFrenchtalkers’firstandsecondvowelformants.Eachpointisavowel,withvowelidentityindicatedbytheappropriateIPAsymbol.Colorindicatestalkerdifferences.

AsshowninFigure5.1,[y]and[u]areacousticallydistinctbasedonthedifferencesin

F1andF2forthefemaleFrenchspeakers.Thissuggeststhelackofaneffectbasedoncue

strengthdoesnotstemfromalackofacousticdifferencesacrossconditions.Further

evidencethatEnglishlistenerscandistinguishthese[y]and[u]stimulicomesfromSteele,

etal.(2015).UsingthesamestimuliasExperiment1A,theyfoundthatnativeEnglish

listenerscanacquirephonotacticconstraintsconditionedon[y]vs.[u]–suggestingthe

stimuliareperceptuallydistinct.

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5.2. AppendixB–Study1pilotstudy

PriortoExperiment1,apilotstudywasrunthatincluded3ofthe4conditions

includedinExperiment1A:NativeShared(2Englishtalkers),WeakDifferent(1English

talkerand1Frenchtalkerwiththe[u]vowel),andStrongDifferent(1Englishtalkerand1

Frenchtalkerwitheh[y]vowel).OtherthantheexclusionoftheNon-nativeShared

condition,thestimuli,design,andprocedureofthepilotwereidenticaltothoseof

Experiment1A.ThepoweranalysisforExperiment1(seeAppendixC)wasbasedonthe

resultsfromthispilot.

Participants

Toreachthetargetof48participants(16percondition)whopassedthe

experimentalcriteria,atotalof85nativespeakersofEnglishwererecruitedonAMT

(passingrateof56.5%).

DataAnalysis

DataanalysiswasidenticaltothatinExperiment1Awithoneexception:theaccent

term,comparingthetwoSharedconditions,wasnotincluded,astherewasonlyoneshared

condition.Thepilotdatawasanalyzedusingalogisticmixed-effectsregression,with

participantresponsesasthedependentmeasure.Fixedeffectsincludedlegality,andtwo

contrast-codedterms:languagedifference(i.e.,Sharedvs.Differentconditions),and

strength(i.e.,Weakvs.StrongDifferentconditions).Interactiontermswereincluded

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betweenlegalityandbothcontrast-codedterms.Randomeffectsincludedrandom

interceptsandrandomslopesbylegalityforbothparticipantsanditems.Inaddition,

follow-upanalyseswererunonindividualconditions,whichincludedafixedeffectof

legality,andrandomintercepts,aswellasslopesbylegalityforitems(themodelsdidnot

convergewithrandomslopesbyparticipant).

PilotResults

Theanalysisrevealedamaineffectoflegality(β=0.49,s.e.β=0.12,χ2(1)=15.23,p

<0.001),suggestingthatparticipantswere,overall,abletolearntheconstraint.Inaddition,

therewasamarginalinteractionbetweenthesharedtermandlegality(β=-0.63,s.e.β=

0.34,χ2(1)=3.31,p=0.07),providingweakevidencethatparticipantsadaptedtoagreater

degreeintheDifferentconditions.Thiswasconsistentwithafollow-upanalysisshowing

thattherewasasignificantdifferencebetweenparticipantresponsesonlegalandillegal

syllablesinbothoftheDifferentconditions(Strong:β=0.73,s.e.β=0.19,χ2(1)=13.1,p<

0.001;Weak:β=0.46,s.e.β=0.19,χ2(1)=6.14,p<0.05),butnosuchdifferenceinthe

SharedNativecondition(β=0.19,s.e.β=0.20,χ2(1)=0.92,p=0.34).Thissuggestedthat

listenersonlyadaptedtotalker-specficphonotacticconstraintsifspeakersdifferedintheir

languagebackground,aswasfoundinExperiments1and2.Therewasnosignificant

interactionbetweenstrengthandlegality(β=0.32,s.e.β=0.30,χ2(1)=1.16,p=0.28),

suggestingbothconditionsprovidedsufficientcuesforlistenerstoidentifyadifferencein

languagebackground,similartoExperiment1.

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5.3. AppendixC–Study1poweranalysis

Thenumberofparticipantswassettoyieldsufficientstatisticalpower(β>.8).

PowerwasestimatedbyMonteCarlosimulationsbasedonresultsfromapilotstudy(see

AppendixBfordetails).Usingtheestimatesforeachfixedandrandomeffectinthelogistic

mixedeffectsmodelfittothesepilotdata,wegenerated1000simulateddatasets.Foreach

simulateddataset,werandomlyandindependentlysampledeachfixedeffectvaluefroma

normaldistribution(withthemeansettotherespectivecoefficientestimateandstandard

deviationsettothecorrespondingstandarderrorestimate)andindependentlysampled

eachrandomeffectbasedontheestimatedrandomeffectdistributions(correlations

betweencoefficientswerenotincorporatedintooursamplingprocedure).Thesewerethen

usedtogenerateasetofrecognitionmemorytestresponse.Wethenfitthesame

regressionmodeltothesesimulatedresponses.(Ifthemodelfailedtoconverge,we

generatedanewsimulateddataset.)Statisticalpowerβwasestimatedbytheproportion

ofthe1000modelsinwhichthecrucialinteractionterm—betweenthefixedeffectsfor

legalityandshared/differentlanguagebackground—wasfoundtobesignificant.We

increasedthenumberofparticipantsiteratively,generatingnovelsimulateddatasetsand

runningnewmodelswitheachiteration,untilwereachedthethresholdofβ>.8.This

thresholdwasreachedwith64participantspercondition(estimatedβ=.804).

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5.4. AppendixD–Study1passingrates

RecallthatexperimentalcriteriainExperiments1Aand1Bwereasfollows:inthe

generalizationphase,participantshadtocorrectlyacceptatleast90%ofpreviouslyheard

items(i.e.,ahitrateofover90%)andcorrectlyrejectatleast10%ofnovelitems.These

criteriaensuredthatparticipantswereabletorecallitemstheyhadpreviouslyheard

multipletimes,andthattheywereabletodifferentiatebetweenpreviouslyhearditems

andnovelitems.InExperiment2,thesecriteriawereloosenedduetothephonological

confusabilityofthestimulusset:thehitratecriterionwasloweredfrom90%to85%.A

thirdcriterionwasalsoadded:listeners’hitratecouldnotexceedtheirfalsealarmrate,to

ensurethatlistenerscoulddifferentiatenovelandfamiliaritems.Forexample,a

participantwithahitrateof85%mustcorrectlyrejectatleast15%ofnovelitems(i.e.,a

falsealarmratenohigherthan85%).

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Table5.1.PassingratesforeachconditionandexperimentinStudy1.

Experiment Condition Totalparticipants

PassingParticipants

PassingRate

1A NativeShared 124 64 51.6%1A Non-NativeShared 101 66 65.3%1A WeakDifferent 118 66 55.9%1A StrongDifferent 112 64 57.1%1B Non-NativeShared 158 66 41.8%1B WeakDifferent 119 64 53.8%1B StrongDifferent 141 64 45.4%2 Non-NativeShared 160 66 41.3%2 Non-NativeDifferent 157 67 42.7%2 MixedDifferent 124 69 55.6%n.b.Thesamenumberofparticipants(64)wereanalyzedineachcondition.Thenumberofpassingparticipantssometimesexceededthisduetotechnicallimitationsinourexperimentalpipeline. AsshowninTable5.1,passingratesrangedfrom41.3%to65.3%between

conditions.Overall,655participantspassedthecriteriaoutof1314participants(49.8%).

Thiswasinlinewithpreviousresultsusingthisparadigm(Denby,etal.,2018).Inapost-

hocanalysis,weinvestigatetherelationshipbetweenthehitrateinthegeneralization

phaseandthelegalityeffect.AsFigure5.2shows,participantswithahitratelowerthan

roughly75%showlittletonolegalityeffect.Thisisunsurprising:if,forexample,a

participantcorrectlyacceptsonlyhalfoffamiliaritems,theyaresimplyatchance,and

thereforewillnotshowanydifferencesbetweenlegalandillegalgeneralizationitems,as

theyarelikelyguessing.Participantswhosehitrateismuchlowerthan50%mayhave

misinterpretedtheexperimentalinstructions,andsimplyanswered“no”toanyitemsthey

hadnotencounteredpriortotheexperiment(ratherthanwithintheexperiment).

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Figure5.2.Scatterplotofhitrate(%yesonfamiliaritems)ingeneralizationphasebylegalityadvantage(falsealarmrateforlegalitemsminusfalsealarmrateonillegalitems)forallexperimentsinStudy1.Eachdotrepresentsasingleparticipant;colorsrepresentwhetherparticipantspassedorfailedcriteria.LinesrepresentLoessregression;shadingrepresents95%confidenceinterval

Notethattherelationshipbetweenhitrateandlegalityadvantageisnon-linear—for

participantswhofailthecriteria,thelegalityadvantagepeaksaroundahitrateof85%;as

thehitrateincreasesto100%,thelegalityadvantagefallsbackdowntoalmost0%.Thisis

alsoanexpectedresult,assuchparticipantsarefailingthecriteriabasedonahighfalse

alarmrate:theyareresponding“yes”toalmosteveryitem,regardlessofwhetheritis

familiarornovel.Detectingdifferencesinresponsepatternsbetweenlegalandillegalnovel

itemsisessentiallyimpossiblewithsuchahighoverallfalsealarmrate.

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Theseresultssuggestthatthecriteriawerenecessarytofilteroutparticipantswho

werebiasedtowardsalwaysresponding“yes”oralwaysresponding“no”,aswellasthose

whoansweredrandomly(i.e.,ahitrateof~50%).Italsoappearsasthoughthecriteria

mayhavebeenslightlytoorestrictive,asparticipantswhosehitratewasaboveroughly

75%appearedtobetrackingtheconstraint,asshownbytheirincreasedlegality

advantage.Inasecondpost-hocanalysis,were-plottedthedatawhilelooseningthe

criteriatoincludeparticipantswithahitrateaslowas75%.AsinExperiment2,we

includedacriterionthatparticipants’falsealarmratemustbelowerthantheirhitrate,to

ensuretheyareabletodifferentiatefamiliarandnovelitems.

Looseningthecriteriaresultedinanadditional152participantspassing,increasing

theoverallpassingratefrom49.8%to61.4%.AscanbeseeninFigures5.3–5.5,the

resultsoftheexperimentdonotqualitativelychangewiththeadditionofthese

participants.Thissuggeststhecriteriaasoriginallysetweresomewhatoverlyrestrictive,

withanadditional~10%ofparticipantsunnecessarilyexcluded.Basedontheseresults,we

recommendthatfutureexperimentswithsimilardesignsshouldloosenthecriteriato75%.

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Figure5.3.LegalityadvantageforExperiment1A,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval.

Figure5.4.LegalityadvantageforExperiment1B,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval.

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Figure5.5.LegalityadvantageforExperiment2,withhitratecriterionloweredto75%.Errorbarsreflectbootstrapped95%confidenceinterval.

134

5.5. AppendixE–Study1modelresults

Table5.2.Experiment1AFixedEffects.

FixedEffect Coefficient StandardError χ2(1) P

(Intercept) 0.30** 0.09 Legality 0.64*** 0.06 73.63 <0.0001LanguageDifference 0.00 0.26 0.00 0.99Strength -0.28 0.18 2.43 0.12Accent -0.34 0.18 3.41 0.06Legality:LanguageDifference 0.72*** 0.20 12.59 <0.001Legality:Strength -0.05 0.14 0.15 0.70Legality:Accent 0.45** 0.14 9.78 <.01Table5.3.Experiment1Arandomeffects.

RandomEffects VarianceIntercept(item) 0.31Slope(itembylegality) 0.06Intercept(participant) 0.91Slope(participantbylegality) 0.06Table5.4.Experiment1Bfixedeffects.

FixedEffect Coefficient StandardError χ2(1) p

(Intercept) 0.52 0.09

Legality 1.02*** 0.07 127.64 <0.0001LanguageDifference -1.06*** 0.19 28.82 <0.0001Strength 0.16 0.16 0.99 0.32Legality:LanguageDifference 0.57*** 0.18 9.81 <0.01Legality:Strength -0.02 0.15 0.03 0.87

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Table5.5.Experiment1Brandomeffects.

RandomEffects VarianceIntercept(Item) 0.36Slope(itembyLegality) 0.06Intercept(Participant) 0.67Slope(ParticipantbyLegality) 0.09Table5.6.Experiment2fixedeffects.

FixedEffect Coefficient StandardError χ2(1) P

(Intercept) 0.97*** 0.08 Legality 0.76*** 0.08 62.83 <0.0001LanguageDifference -0.20 0.19 1.13 0.29Native 0.14 0.19 0.52 0.47Legality:LanguageDifference 0.71*** 0.21 11.08 <0.001Legality:Native -0.04 0.21 0.03 0.87Table5.7.Experiment2randomeffects.

RandomEffects VarianceIntercept(item) 0.15Slope(itembyLegality) 0.08Intercept(participant) 0.45Slope(participantbyLegality) 0.09

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5.6. AppendixF–Tonguetwistersamplesizeanalysis

Ananalysisof15previoustonguetwisterexperimentsforwhichdesigndetailsand

resultswereaccessiblefoundawiderangeoftotalnumberofsyllablesanalyzedanderror

rates(seeTable5.8).Theaveragenumberofitemsanalyzed(wordsorsyllables,depending

onthedesignoftheexperiment)was49,152(rangeof9,216-184,320).Thecurrent

experimentexposesparticipantstosecond-orderconstraints;theaveragenumberofitems

forpreviousexperimentswithsuchconstraintswas53,453(rangeof18,432-82,944).

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Table5.8Numberofitemsanalyzed(wordsorsyllables),errors,errorrates,andconstraintorderforprevioustonguetwisterexperiments.

Paper Experiment TotalItems

TotalErrors

ErrorRate

Order

Delletal.(2000) 1 36,864 3065 8.3% 1stDelletal.(2000) 2 36,864 3584 9.7% 1stDelletal.(2000) 3 36,864 1769 4.8% 2ndGoldrick(2004) 1 184,320 6762 4.8% 1stKittredge&Dell(2016)

1 64,512 5010 5.7% 1st

Smalleetal.,(2017) 1-Adults 55,296 1240 2.2% 2ndTaylor&Houghton(2005)

1 36,864 1313 3.6% 1st

Taylor&Houghton(2005)

2 9,216 745 8.1% 1st

Taylor&Houghton(2005)

3 9,216 729 7.9% 1st

Warker(2013) 1 82,944 3926 4.7% 2ndWarker(2013) 2 55,296 3355 6.1% 2ndWarker&Dell(2006)

1a 18,432 500 2.7% 2nd

Warker&Dell(2006)

1b 18,432 1074 5.8% 2nd

Warker&Dell(2015)

1 55,296 4043 7.3% 1st

Warkeretal.(2008) 1 73,728 5460 7.4% 2ndWarkeretal.(2009) 1 18,432 391 2.1% 1stAninitialpilotexperimentwaspreviouslyconductedwith9,216totalitemspercondition

(36,864total).11ofthe32participantsessionswereanalyzedforerrors,foratotalof

12,672items.Atotalof433errorswerefound,foranerrorrateof3.4%.Thiserrorrate

waswithintherangeofpreviouslyfounderrorrates,althoughitwasonthelowendofthe

range.Thelowerrorrate,however,andtherelativelysmallnumberofitems,renderedthe

resultsuninterpretable,especiallywhensplitbycondition.Thecurrentexperiment

increasesthesamplesizeto110,592(27,648percondition;seeabovefordetails).

138

5.7. AppendixG–Study2modelresults

5.7.1. Within-conditionmodels;allsessions;[m]-[n]swapsincluded

Table5.9.Differentcondition;allsessions;[m]-[n]swapsincluded.

FixedEffect Coefficient StandardError χ2(1) P(Intercept) 0.32 0.14

Constraint -0.97*** 0.19 25.86 <0.001Session 0.28 0.18 2.34 0.13Constraint:Session 0.44 0.36 1.48 0.22

RandomEffects


0.46

Table5.10.NativeSharedcondition;allsessions;[m]-[n]swapsincluded.


Constraint -0.92*** 0.17 30.74 <0.001Session 0.1 0.16 0.38 0.54Constraint:Session -0.61 0.31 3.91 0.05

RandomEffects


0.43

139

Table5.11.Non-NativeSharedcondition;allsessions;[m]-[n]swapsincluded.


Constraint -1.64*** 0.21 64.2 <0.001Session -0.27 0.18 2.25 0.13Constraint:Session 0.42 0.36 1.36 0.24

RandomEffects


1.2

Table5.12.Vowelcondition;allsessions;[m]-[n]swapsincluded.


Constraint -1.47*** 0.28 26.9 <0.001Session 0.11 0.27 0.16 0.69Constraint:Session 0.66 0.54 1.51 0.22

RandomEffects


0.86

5.7.2. Within-conditionmodels;[m]-[n]swapsexcluded

Table5.13.Differentcondition;allsessions;[m]-[n]swapsexcluded.


Constraint 0.49 0.26 3.8 0.05Session 0.27 0.25 1.21 0.27Constraint:Session 0.39 0.49 0.63 0.43

RandomEffects


0.34

140

Table5.14.NativeSharedcondition;allsessions;[m]-[n]swapsexcluded.


Constraint 0.38 0.21 3.33 0.07Session -0.06 0.21 0.09 0.76Constraint:Session -0.78 0.41 3.58 0.06

RandomEffects


0.26

Table5.15.Non-NativeSharedcondition;allsessions;[m]-[n]swapsexcluded


Constraint 0.01 0.25 0 0.97Session -0.3 0.23 1.68 0.2Constraint:Session 0.38 0.45 0.69 0.41

RandomEffects


0.42

Table5.16.Vowelcondition;allsessions;[m]-[n]swapsexcluded.


Constraint 0.13 0.38 0.11 0.74Session 0.19 0.37 0.28 0.59Constraint:Session 0.8 0.73 1.22 0.27

RandomEffects


0.81

5.7.3. Within-conditionmodels;session1excluded;[m]-[n]swapsexcluded

141

Table5.17.Differentcondition;session1excluded;[m]-[n]swapsexcluded.


Constraint 0.73* 0.35 4.76 0.03

RandomEffects


0.81

Table5.18.NativeShared;session1excluded;[m]-[n]swapsexcluded.


Constraint -0.01 0.31 0 0.98

RandomEffects


0.54

Table5.19.Non-NativeSharedcondition;session1excluded;[m]-[n]swapsexcluded.

FixedEffect Coefficient StandardError X2(1) p(Intercept) 1.39 0.2

Constraint 0.14 0.33 0.18 0.67

RandomEffects


0.38

Table5.20.Vowelcondition;session1excluded;[m]-[n]swapsexcluded

FixedEffect Coefficient StandardError X2(1) p(Intercept) 2.13 0.42

Constraint 0.62 0.61 1.13 0.29

RandomEffects


1.57

142

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