Toseeacuponthetable is toseeaparticular individual—that very cup —withitsvariousqualities,locatedinrelationtoothervisualob-jectsandproperties.Perceptualexperiencesliketheseseemtopossessdemonstrative content;theexperiencesseemtobeaboutorrefertopar-ticularindividualobjects.
Visualandauditoryexperiencescanbeaboutorrefertoobjects(orevents)evenwhenthoseobjectsare locatedfarawayfromourbodies.Inaddition,thesemodalitiesseemtodirectlyrepresentdis-talobjects,withoutrepresentinganyintermediaryconnectingustothem. I see the cup without seeing the light contacting my retina.I experience a distant sound as located far away, not as travellingthroughtheairfromitssourceallthewaytomyears.Thesemodali-tiescanbedescribedasteleosenses:theycanrepresentdistalobjectswithoutrequiringthatwerepresentsomethingelseconnectingustothoseobjects.Bothvisionandauditionrepresentobjectsandtheirfeatures as located at a distance from our bodies, and neither in-volvesdirectcontactwiththeobjectsofourdistalexperience.Touchisnota teleosense.Whereaswecanseeanobject fromacross theroom, or hear a voice calling out from a distance, touch seems torequiredirectcontactwiththeobjectsofourexperience.Weseemincapable through touch of reaching out beyond the limits of ourbodies,ofexperiencingtheworldbeyondourskin.Wefindaquar-ter in our pocket by feeling the contact it makes with our fingers.Weturnonthelightintheclosetbyfeelingarounduntilourhandmakescontactwiththeswitch.Indeed,onemeaningof‘touch’isjusttohaveourbodiescomeintocontactwithsomething,evenifitdoesnotelicitaperceptualexperience.
phenomenal states. Beliefs are paradigm intentional states; theypoint toorare aboutstatesofaffairsintheworld.Suchstatespossesssome referential component. Perceptual experiences are paradigmphenomenal states. They involve a particular phenomenal charac-ter,orfeel.Butmyassumptionisthattheyalsohaveanintentionalcomponent.PerceptualexperiencesseemcompletelyintentionalinBrentano’ssense:likebeliefsandthoughts,theyareaboutthingsintheworld.Whenweseearedappleonthetable,ourexperienceisrepresentingacertainstateofaffairs.Thisisabasicsenseofrepre-sentationthatmostwouldagreeon.Whilesomephilosophershaverecently argued that phenomenal states just are intentional statesof a certain kind (e. g., Dretske 1997, Tye 1997, Byrne 2001), this isnot required for perception to possess a referential character. Theviewdoesnot,forinstance,requireanexplicit,fullydetailedmentalrepresentation of the state of affairs, nor does it require that thephenomenalcharacterbefullyexhaustedbysuchrepresentationalcontent.Inaddition,Iassumethatperceptualexperiencesgrounddemonstrative thoughts about objects in the world (Siegel 2002,Campbell2000)andareassessableforaccuracy(Siegel2010,Schel-lenbergforthcoming).Usingtheserelativelymodestassumptionsasafoundation,thispaperdevelopsanaccountofthereferentialchar-acteroftypicaltouchexperiences.
What follows is an account of the relation that holds betweentouchexperiencesandtheobjectsofthoseexperiences.Itis,essen-tially, an account of perceptual reference in touch. I argue that intouch,as invisionandaudition,wecanandoftendoperceiveob-jectsandpropertiesevenwhenwearenotindirectorevenapparentbodilycontactwith them.Unlike thosesenses,however, touchex-periencesrequireaspecialkindofmutuallyinteractiveconnectionbetweenoursensorysurfacesandtheobjectsofourexperience. Icall thisconstraint theConnection Principle. Inotherwords, tactualreferencetoanobjectrequiresanappropriateconnectiontothatob-ject,eitherdirectlyorthroughsomeconnectingmedium.Touch,onthisview,issomethingofaninbetweensense,notafullteleosense,butalsonotacontactsense.Rather,itisaconnection sense:wecanexperiencedistalobjectsthroughtouch,butunliketheteleosenses,wecandosoonlyifthereisanappropriateexploratoryconnectionbetweenourbodiesand theexternalobject.1Thisviewhas impor-tantimplicationsfortheproperunderstandingoftouch,andpercep-tual referencegenerally. Inparticular,spellingout the implicationsofthisprincipleyieldsarichandcompellingpictureofthespatialcharacteroftouch.
2. The Contact Thesis
I start with the assumption that perceptual experiences containsomedemonstrativereferentialcomponent.2Philosophershavetra-ditionally recognized a distinction between intentional states and
WecanfindamoreplausibleversionofCTsuggestedbyMichaelMar-tin(1992).6Ratherthanappealtotheactuallimitsofthebody,Martinsuggeststhatweappealtoitsapparentlimits.Martinappealstothewell-established fact that our body schema is malleable: where ourbodyisfeltorexperiencedtoendisnotnecessarilywhereitactuallyends(1992,201–2).Thusbodilyfeelingneednotoccurwithintheac-tual limits of one’s body, but only within the apparent limits of thebody.ThisleadstothefollowingmodificationofCT:
Apparent Contact Thesis (ACT): Tactual object of per-ceptionoccursonlyattheapparentsurfaceorlimitofthebody;referencetoanexternalobjectintouchcanoccuronlywhentheobjectisindirectcontactwiththeappar-entlimitsofthebody.
Martin argues that bodily sensations are always felt as located onone’sbody.Thustouchexperiences(whichplausiblydependonsuchsensations)mustinvolveanexperienceofanobjectincontactwiththeapparent limitsof thebody.Anyspacebeyondourbodysimplycouldnotbeapossiblelocationforabodilysensation:“theapparentlimitsofthebodyaretheapparentlimitsofpossiblesensation”(202).Since we experience objects only when they cause sensations, andthesesensationsarealwayslocatedonthebody,itwouldseemtofol-lowthatwecanexperienceobjectsonlywhentheycomeintocontactwiththeapparentlimitsofourbodies.
touchonlywhentheycomeintocontactwithourbodies.Appearancesare deceptive, however. It is relatively easy to find touch experienc-es that violate CT. Whenever one touches an object while wearinggloves,forinstance,oneperceivesanobjectthatisnotindirectcon-tactwiththesurfaceofthebody.Whenonepicksupapencilwhilewearinggloves,onestillhasatactualexperienceofthepencil,notoftheglovenoranythingbeyond.Suchexamplesarenotrestrictedtosomethingasthinaslatexgloves(whichonemightthinkarebarelyregisteredbyourtactualreceptors).Onecanfeelthesurfaceofthefloor through one’s socks and shoes, feel the keys in one’s pocketbypressingontheoutsideofthefabric,orfeelthemovementsofapuppywrigglingunderablanket.CTisevenmoreclearlyfalseifwedefinethelimitsofourbodiesasthelimitsofoursensorysurfaces(the specialized transducers within the glabrous and hairy skin).3 Most touch receptors lie deep within the dermis, under many lay-ersofdeadcellsintheepidermis.Alltouchexperienceswouldthusseemtooccurthroughsomemediatingmaterialthatliesbeyondouractualreceptors(seee. g.,LumpkinandCaterina2007,andMollet al. 2005).4 In addition, there are no transducers in our fingernails,yet we are able to perceive a range of tangible properties throughournails.5 Ihavenotevenmentionedthewidevarietyofcomplextouch experiences involving tools and other intermediary objectsthatwouldalsoviolateCT.
3. While no recent thinkers have claimed that touch begins at the recep-tors (rather than thebody), that tactual information is reliably transmittedthroughinertlayersofskin,nails,andteethlendsadditionalintuitivesupporttothepositiveviewtobedefendedlater.
Driving:Youaredrivingacar.Younotice,throughyourtactual experience alone, that the road changes fromsmoothasphalttogravel.Youmayeventhinktoyourself,
“Thissectionofroadisrough.”
Thisisacaseofatactualexperience—mediatedbyvibrationandpres-sureonthesensorysurfacesoftheskin—whichrepresentsapropertyoftheroad,itsbeingrough.10Yourexperienceis of the road,itisnotanexperienceofthewheelorthecarframe,andcertainlynotof the seat.Itisanexperienceof theroaduponwhichyouaredriving; theroad istheobjectofyourexperience.Thisexperience,Iwouldargue,isnotabodily(orevenbodily-directed)experience,forinstance,ofyourbodyvibratingagainsttheseat.Itisanexperienceoftheroad.Theexternallydirectedexperienceofyourbackagainsttheseatisadifferentexperi-ence,inbothitsphenomenologyanditscontent,fromtheexperienceoftheroad.Thebodilyawarenessinsuchanexperienceislargelyimplicitandinthebackground.Thatis,weneednotassignanyintrinsicsensory
awareoftheglassbybeingawareofthepartsonetouches”(1992,200).Thisquotesuggeststhatweareawareoftheglassasawholeonlyinvirtueofawarenessofthepartsbeingtouched.Wehavenoexperienceofwhatliesbetweenthefingersoroftheglassasawhole;thepointsof contact are the only locations of which we experience (for thesearetheonlylocationsofpossiblebodilysensation).Theexperienceofbodilycontactisthatwhichrevealsormakesmanifestthepropertiesoftheimpingingobject.AsMartinsays,“Onemeasuresthepropertiesofobjectsintheworldaroundoneagainstone’sbody.Soinhavinganawarenessofone’sbody,onehasasenseof touch”(203).7Contraryto this view, I believe that we can and do have tactual experiencesofdistalobjectsevenwhenthoseobjectsarenotincontactwiththeapparentlimitsofourbodies.WhileIthinktouchdoesinvolvesomeconnectionwithexternalobjects,theobjectofourexperienceneednotbeindirectcontactwiththeapparentlimitsofourbodies.
andtrackthecatasitnavigatesaroundobstaclesandmarchesonto-wardyourface.Theexperienceofthecatanditslocationismediatedhereentirelybytouch,eventhoughthecatisclearlylocatedbeyondthe range of the body, and also beyond the apparent limits of yourbody.Suchacomplex touchexperienceundermines theplausibilityofACT,forthereisnosenseinwhichtheapparentlimitsofthebodyextendtoincludethemattressandthebed.
Despite thesecases,wecanagreewithMartinthatalterations inbodyschemadooccur.Phantom-limbpatientsclearlyseemtoexperi-encesensationsinlimbsthatonlyapparentlyexist,andaprofessionaltennisplayermayexperienceherracketasaliteralextensionofherbody.Wecanevenagreethatsuchalterationsarecommon.Itseemsreasonable,forinstance,tothinkthatevenwearingahatoraheavycoataltersourperceivedsenseofbodilyspace.However, it is incor-recttosupposefromsuchcasesthatallextendedtactualexperiencesinvolveareorderingofone’sbodysense.Inthedrivingexample,itisunlikelythatIexperiencetheseatorthecaritselfasanextensionofmybody.Similarpointscanbemadeaboutcat-tracking.Istillhaveanexperienceofthelimitsofmybody,andthisisanexperienceofmybodyassittingontheseatorthebed,notascontinuouswithorapartoftheseat,orthecarframe,axle,orwheels.Outsideofthepointsofcontactwiththeseat,therearenogood,principledcandidatesfortheapparentlimitsofmybodythatexplainmyexperienceoftheroad.Ifmybodyimageweretoexpandtothewholecar,forinstance,thenIoughttoexperienceapassengerassittinginsidethelimitsofmybody.Clearly,thisdoesnothappen,andwemustconcludethatcaseslikecat-tracking,driving,orevenusingapenciltofeeltheroughnessofpaperareavarietyofdistaltouchthatviolatesACT.
12. One might worry that this is a mischaracterization of the experience; thatratherthananexperienceof theroad,drivinginvolvesaninferenceor judg-mentabouttheroadbasedontheproximalexperience(muchaswebecomeawarethatwearerunningoutofgasbylookingatthegauge).IwilladdressthisworryindetailinSection6.
13. Iwishtobecautiousinmyuseof“causal”here.Itmaynotbecorrecttosaythatwealwaysrepresenttoourselvesacausalconnectioninsuchanexpe-rience. Indeed, when driving we may simply experience the road directly,withoutrepresentingtoourselvesthefactthatitistheroadthatiscausingourexperiencesintheseat.Thusitmayturnoutthattactualprojectionin-volves an implicit or automatic extension of experience to a distal object.Still,evenif it isnotanexplicitrepresentationofacausalconnection,theexperienceofadistalobject through touchseemsbest characterizedasaprojectionthroughourtotalproximateexperiencetothatwhichiscausallyconnectedtoit.Iwillreturntotheseissues.
Westartedwiththeobservationthattouchappearstobeacontactsense. Initially, this was understood as the claim that touch, unlikethedistalsenses,cannotrepresentobjectsorpropertiesnotindirectcontact with our bodies. This claim has now been rejected on thebasisofclearcounterexamples.Nevertheless,therestillseemstobesomethingimportantintheclaimthattouchrequirescontact:touchseemstoneedsomeconnectiontotheobjectsweexperience.Follow-ing Evans (1982), I suggest that tactual reference requires a stronginformational linkbetweenanobjectandoursensorysurfaces.Wecannothaveanexperienceofanobjectifthatobjectisnotconnectedtousintheappropriateway.Onecannotexperienceaspherethroughtouchifthesphere(oritsproperties)isnotconnectedinsomeappro-priatemannertooursensorysurfaces:
Connection Principle (CP): Tactual reference to an ob-jectrequiresanappropriatetactualconnectionwiththeobject,eitherdirectlyorthroughsomeintermediary.
Anythingthattransmits informationaboutdistalobjects,andtherebyallowsustohavegenuinetactualexperiencesoftheseobjects,countsasatangible medium.Thiswillincludevariousobjects,tools,voluminousmaterials,andevenorganicsubstancesasfingernails,epidermis,andhair.Touchisaconnectionsense,butthatdoesnotmeanthatitisn’tdistal. It can represent objects located some distance from the body,butonly if thoseobjectsareconnectedtous intheappropriateways,throughtheappropriatechannels.Connectiontoanobjectisnecessaryfortactualreference.We’lllookatthenatureoftheselinksinamoment.First,letmeemphasizethattheinformationalconnectioninvolvedhereis not sufficient but only necessary for perceptual reference in touch.Wecannotsecurereferencethroughabarecausalorinformationalcon-nectionwithoutsomeexperientialcomponent.Weneednotexplicitlyexperience theconnection inorder toproperlyconnect theproximalstimulations with the proper external object. Instead, the kinds of in-formationallinksthatconnectusthroughtouchlendthemselvestothe
experiencereferstoaparticularobjectinvirtueoftheinformationallinksconnectingtheperceptualstatetotheobject.AsEvanscorrectlynotes, such links are not sufficient to ground perceptual reference;however, I think he was correct that some such link is a necessaryconditiononperceptualreference.Thisinsightallowsustodevelopamoreplausibleaccountoftactualreference.
Toseethismoreclearly,imaginesomethingfurtherremovedfromourskinthanapencilorgloves.Itisunlikelythatwewouldexperi-ence a broomstick or a shovel as defining the limits of our bodies,thoughwecan justaseasilydrageitheralong theground todeter-mine its texture and hardness, or probe the walls of a dark roomtodetermine its shape. It ismuch thesamewithstilts,bikes, rollerskates,orotherextensionsofourtactualabilities.Thatweprojectourexperiencestodistalobjectsdoesnotshowthatweprojectourbody-sense.Itisnotthecasethatwheneverwetouchanobjectwithsomemediatingobject,weincorporatethemediatorintoourbodyimage.Itisfarmorelikelythatweexperienceonoursensorysurfacesstimulithatgiveusconsistentinformationaboutdistalobjects,informationthatismerelytransmittedthroughsomeintermediarytoolorobjectwhich is not itself the object of our experience. This initial insightleadsustomypositiveaccount.
5. The Connection Principle
We often experience objects through touch that we are not in directcontactwith,andthatarenotincontactwiththeapparentlimitsofourbodies.Tactualreferencethereforecannotbeexplainedintermsofsuch(apparent) contact. A plausible means of understanding tactual refer-enceisneeded.IbeginfirstbysuggestingaprinciplethatcanreplaceACTandthatcanaccountforthewidevarietyofdistaltouchexperienc-es.I’llthenconsiderandrejectacloselyrelatedalternativetothisview.Finally,I’llconsiderthecriticalquestionofwheredistaltouchobjectsarerepresentedasbeing.Theanswertothisfinalquestion,groundedinthedistinctionbetweendifferentlevelsofspatialrepresentation,willofferaplausiblegeneralaccountofthespatialcharacteroftouch.
evenorganicsubstancessuchasfingernail,epidermis,andteeth—re-liablytransmittangibleinformationaboutdistalobjectsandtherebyallow us to experience those objects. Slack string, for instance failsthistest:itsimplycannottransmittheappropriateinformationtoourtouchreceptors.Pencils,gloves,walkingsticks,andamyriadofothertoolsandobjectsdoreliablytransmittangibleinformationandcountas tactual media. These media transmit tangible properties, whichincluderoughness,solidity,weight,elasticity,vibration,andthermalproperties,alongwithmanyothers.Sometangiblepropertiesaremoreeasilytransmittedthroughtangiblemedia.Thesetendtoberelativelysparsepropertieslikeroughnessandsmoothnessthatdonotinvolveprecisespatialresolutions.Othertangibleproperties,likefinetexture,exactshape,contours,andpart-wholerelationships,aremoredifficulttotransmitthroughtactualmedia,thoughsomemediaexistthatcantransmitsuchinformation(thingloves,forinstance).Aconnectionisappropriate for touch, then, if it involves tactualmedia thatcanreli-ablytransmitinformationaboutdistaltangiblefeatures.
Wecansayabitmoreabout theconnection.Formanytouchex-periences,theconnectionseemstobecloselyrelatedtoexplorationandcontrol.Considerasimplecaseofdistalthermaltouch.Withyoureyesclosedorblindfolded,youcanexperiencetheheatcomingfromacandlesetbeforeyou.Theexploratoryactionsyouperformrelativetothecandle—perhapsmovingyourpalmaroundinfrontofyou,feelingfortheheattoincreaseordecrease—allowyoutoexperiencetheheatascomingfromanexternalsource,locatedinaparticularspot.Itisthewayinwhichtheexperienceoftheheatchangesrelativetoourmove-mentsthatsecuresthedistalnatureoftheexperience;weexperiencethe heat as located at a distance from our bodies because our heatexperiencesareappropriatelylinkedtoourmovements.
The same is true of distal touch involving tools. When we use apencilortongstotouchobjects,weareabletomoveandmanipulatethedevicesindifferentways,allowingforcoherentandstablerepre-sentationsofobjectslocatedawayfromthebody.Whenweusesuchatool,orexperienceanobjectthroughasoftintermediary,itisnotin
rightkindofimplicitawareness(skillfulsensorimotorconnections,forinstance). In this respect, the CP is in line with the kinds of connec-tionsEvansoriginallyenvisionedwithhisnotionofinformationallinks,supplementedbyappropriateexploratorymechanisms.
Whatkindsofconnectionswouldbeappropriate,then?I’mgoingtostartwithanideadiscussedbyEvans(1982).Accordingtohim,“demon-strativethoughtstakeplaceinthecontextofacontinuinginformationallinkbetweensubjectandobject”(1982,146).Thisinformationlinkpro-videsasubjectwithagoverningconceptionof theobject,keepsthesubject “incontact”with theobject for thepurposesof trackingandupdating,andallowsthesubjecttolocatetheobjectinegocentricandallocentricspace(173–4).Evansiscleartoemphasizethatthelinkisnotsufficientfordemonstrativethought,butthatitneedstobeappropri-atelyassociatedwithourthoughts.Therearemanypositiveaspectsofthisview.Theviewistemporallyextended,allowingthenaturalincor-porationofextendedtouchexperiences.Theviewisinherentlyactiveand exploratory. It accommodates circuitous information links. Andfinally,itoffersarelativelytouch-friendlymodelofspatialrepresenta-tion.Despitethesestrengths,italsosuffersfromsomeweaknesses.ForEvans,theinformationlinkseemstobeunidirectional,withinforma-tionfromobjectsintheworldconnectedtoandupdatingourthoughts.Buttheinformationlinksintouchseemmutuallyinteractiveandbidi-rectional.Whenwepressandpullagainstanobjectwebothchangetheobjectinvariouswaysandreceiveupdatedinformationfromthatobject.AnotherworryisthatEvansdownplaystheimportanceofsen-soryexperienceindemonstrativethought,butouraccountoftactualreferenceoughttomakesomereferencetothequalitativecharacteroftouchexperiencesinvirtueofwhichtheycanbeaboutparticularob-jects.Andfinally,Evans’accountofspatialcontentscanberevisedinlightofrecentempiricalevidencetoofferamoreplausibleaccountoftangiblespace.Withthisrevision,wecannowputforwardadetailedaccountofwhatanappropriateconnectionamountsto.
First, let me introduce the notion of tactual media. Such me-dia—which includevariousmaterialobjectsandtools,andperhaps
BeforedevelopingtheconsequencesanddetailsoftheCPaccountoftactualreference,itwillbeusefultocontrastitwithanothercloselyrelatedview.Thisalternativeremovestheimplausibleclaimthattheobjects of tactual experience must be in apparent contact with ourbody,andittoocaninvokeaconnectingelementbetweenourbodiesandthedistalobjectofexperience.Itdiffershowever,inmaintainingthatwemusthaveadirect,explicitexperienceoftheobjectthatisindirectcontactwithourbody.CallthistheMediated Contact Thesis:
Thebasicideaisthatsomeexperiencesmediateotherexperiences.Such mediation is common in the other senses. We cannot see thewinddirectly,butwecanstillbecomeawareofthewindbyseeingtheleaves rustle along the ground. Similarly, we cannot see the moon-landingdirectly,butwecanstillexperienceitbywatchingavideoofitonatelevisionscreen.MCTholdsthatdistaltouchalsohasamedi-atedstructure,thatourexperienceofthedistalobjectismediatedbysomemoreproximalexperienceofanobjectthatisindirectcontact
somerandomorchaoticmanner;rather,wefeelstableinformationthrough the intermediaries. We are, in a sense, able to feel throughthemtotheobjectontheotherside.Whenweexplorethroughtouch,weareable togroundandrepresentcertainpropertiesas located incertainplaces.Thesameis trueof theuseof tools for tactualprojec-tion,whichoccurswhenthemediumbecomes,inacertainconstrainedsense,transparent.
Wecanfurtherclarifythesepointsbysayingthattheinformationlinkoughttomeshwithourexploratory procedures (EPs).14LedermanandKlatzky(1987)introducedthisnotionafterdiscoveringthatsub-jectsalwaysusedasetofstereotypicalexploratorymovementswhentouching objects in an unconstrained setting. These EPs includemovements,likeunsupportedholding,pressing,andcontourfollow-ing, that allow a subject to engage directly with objects in order todeterminesetsoftangiblefeatures.Theuseoftactualmediamustal-lowforthesmoothincorporationandextensionoftheseexploratorymovements.Thatis,theactionsweperformwithtoolsandothertac-tualmediamustcoherewiththekindsofEPswewouldnormallyusewhentouchingobjects:weshouldbeabletopressandtapandslidetactualmediaacrossasurface,forinstance.Thisexplainswhywecanexperienceadistalsurfacewithapencilbutnotwithslackstring:wecannotperformanyexploratoryprocedureswithsuchastring.
Thattouchmakesuseofamediumshouldnotbeparticularlycon-troversial.Thedistalsensesallinvolvestimulationsthatarriveatthesurfaceofthebodythroughamedium.AsAustenClark(2000,Chap-ter1)notes,theappearanceofspaceingeneralismysterious.Touchshould be no more so. Through touch we are sensitive to pressurewavesandvibrations,aswellasothersimilarsignals,andthesestimuliarecapableoftravelthroughmediajustlikelightandsoundwaves.Itthusmakessensethatourtouchreceptorscouldbringusintocontact
experiences:onecouldnothavethemediatedexperiencewithoutthemediating one. The mediated qualitative properties we experiencedepend on those of the mediating one: on different television sets,theFenwaygrassmayappearmoreyelloworbluethanitactuallyis.Butnote: inmanyof thesecases,while themediatingexperience iscausallynecessaryforthemediatedone,itneednotbeanexplicit,at-tendedexperiencethatdoesthemediating.Themediatingexperiencecanremainimplicit,partofthebackground.Forexample,onecanbefullyengrossedinthedepictedeventsofamoviewithoutpayinganyattentiontothechangingproximalpropertiesof thescreen.Wecanseethroughthescreendirectlytotheobjectsandeventsbeyond.Suchmediatingexperiencescanthusbequitethin,sofarasexperiencesgo.
Call thefirst inferential mediation.Suchmediationoccurswhenaperceptual experience allows us to become aware of some state ofaffairs.15 Contrast this with experiential mediation, which involves aperceptual experience that depends on some other perceptual ex-perience.Amongotherways,wecandistinguishthesetwokindsofmediationbyhowtheydifferintheassignmentofqualitativesensoryfeatures.Tohavean inferentiallymediatedawarenessofxviaaper-ceptualexperienceofyinvolvesnoqualitativeawarenessofsensoryfeaturesofx.Whenweexperiencethewindbyseeingtheleaves,wedonotexperienceanysensoryfeaturesofthewind;whenweseethatthetankishalffullbylookingatthegauge,wedonotexperienceanysensoryfeaturesofthegasinthetank;whenwebecomeawareofthefirebyseeingitssmoke,wedonotexperienceanyfeaturesofthefireitself.Webecomeawareofthesethingsonthebasisofperception,butstrictlyspeaking,wedonotperceivethem.Rather,weinferx,perhapsevenquicklyandseamlessly,fromtheperceptualexperienceofy.
Cases of experiential mediation are different. In experientialmediation, we perceptually experience the sensory qualities of x byexperiencingthesensoryfeaturesofy.Watchingtelevisionisagoodexample.OnecanseethegreengrassofFenwayParkbysee-ingthegreenpixelsonone’stelevisionset.Hereaqualitativesensoryfeature—greenness—isbeingassigneddirectlytothegrass;thecolorofthefieldisnotsimplyinferredfromourexperienceofthetelevisionpixels, it is perceptually experienced (seeing something on a televi-sionisstillakindofseeing).Anotherexampleisrecordedsound.Wecanhaveauditoryexperiences that refer toaparticularvoicebyex-periencing a recording of that voice. In both cases, the experiencesaremediated;wehavetheoneexperience(ofthegreengrass,ofthevoice)onlybecausewehavesomeotherexperience(ofthetelevision,oftherecording).Thereisarelationofdependencebetweenthetwo
15. Whether to call the inferred representation an “experience” is a difficultquestion.
TheCPaccountoftactualreferenceisconsistentwithaversionofMCT inwhichdistal touchexperiences requireonlybackgroundorimplicit experience of the proximal points of contact. Consider twocases:feelingtheroughnessofpaperwithapencil,andtouchingata-blethroughgloves.Inthefirstcase,wedonotexperiencethepaperbyattendingtothepencilincontactwithourfingers(apointdiscussedearlier). The pencil is a tactual medium that is reliably transmittingtangibleinformationaboutthepapertoourhands.Sothereisgoingtobesomebodilyawarenessofourfingers(akindofbackgroundaware-nessofourfingers,say),butourfingersthemselvesneednotbecomethedirectobjectsofexperience,norneedweattendtothem,norneedwe be able to have a demonstrative thought about them (all usefultestsfordistinguishingimplicitfromexplicitawareness).Similarly,weneednotattendtotheinterioroftheglovesinordertoexperiencethetable. We can simply experience the table, without any more directproximalawareness.
Whatmustbeemphasizedabouttouchisthatitinvolvesnomediatingfieldofsensation….Intouchabodyinves-tigatesbodiesasonebodyamongstothers,forintouchwe directly appeal to the tactile properties of our ownbodiesininvestigatingtheself-sametactilepropertiesofotherbodies.[1989,38]
According to O’Shaughnessy, our experience of external objectsthroughtouchalwaysinvolvesadirectawarenessofourownbodies,sowecanexperienceobjectsonlywhensomethingimpingesuponthe body and (importantly) when we are aware of that impinging.Vision and the other distal senses involve no mediation throughbodilyawareness;wecaneasilyseeanobjectlocatedsomedistance
Theotheroptionisthattouchinvolvesexperientialmediation.Thisisimplausibleifconstruedastheviewthatdistaltouchismediatedbyanexplicit,foregroundawarenessofthemediatingexperience(asstat-edinMCT).Wecanseethisbyappealtothecloseconnectionbetweenattention and demonstrative thought (and this connection works aswell in the inferential case discussed above). If we perceptually at-tendtoanobject,thenthatexperienceshouldgrounddemonstrativethoughtsabouttheobjectofourattention.Forinstance, ifmyvisualexperienceinvolvesexplicitawarenessofaredboxonthetable,suchanexperienceshouldgroundademonstrativethoughtabout“thatredboxonthetable”(cf.Siegel2002,CampbellandMartin1997).Ifdistaltouchexperiencesoccurinvirtueoftactualreferencetotheproximalobject,thenanyexperienceofadistaltouchobjectoughttogroundreferencebothtothedistalobjectandtotheproximalobject.Soanexperience of the paper through a pencil should ground thoughtsabout“thispencil”aswellas“thispaper”.Butitseemsclearthatdistaltouchexperiencesofteninvolvenoproximalexperiencesthatcouldgrounddemonstrativethought.Icanexperiencethedistalobject(thepaper)withoutbeinginapositiontothinksomethingabouttheprox-imalobject(thepencil).Thisisbecauseeveniftheyarepresent,theproximalexperiencesareunattendedandremaininthebackground.Whilewemayhavesomeimplicitexperienceoftheproximalpointsofcontact,wealmostneverattendtosuchexperiences,leavingthemunabletogrounddemonstrativethoughts.Forthisreason,theclaimthatdistaltouchinvolvesattended,explicitawarenessoftheproximalobject(asseemsrequiredbyMCT)cannotbeanecessaryconditionondistaltactualreference.
Halliganet al.2003).Onmoststandardaccounts,thereare(atleast)threedistinctframesofspatialreference.First,thereisinternalorper-sonal space,whichisthespaceoccupiedbyourownbodies.Anitchonthearmorapangofhungerlocatedsomewhereinthebellyareexamplesofrepresentationswithinone’spersonalspace(Halliganet al.2003).Thelocationsinvolvedhereareegocentric,relatingvariousbodypartswitheachotherwithoutconcernfortheirobjectiveloca-tionsinspace.Inadditiontopersonalspace,thereisextrapersonalorexternalspace.Lookingoutontoafieldofflowersinvolvesrepresent-ingobjects inexternalspace.Theymightberepresentedrelative tootherexternalobjectsorlandmarks,buttheyaretakentohaveasta-bleandobjectivelocation“outthere”.Ithinkthatpriorviewsoftouchhaveassumed,incorrectly,thatthesearetheonlyframesofreferencerelevanttoperception.Thedistalsenseshavebeentakentooperateinexternalspace,representingobjectsandpropertiesrelativetosomeexternal frameofreference.Touch,ontheotherhand,hasbeenrel-egated topersonalspace,and itwasassumedto represent featuresonlyrelativetothebody(hencethecentralityofbodilyawarenessattheproximalpointsofcontact).SuchaviewseemstojustifyaviewlikeACT.Astrongargumentmightbemadefortheviewonthisbasis,wereitnotfortheexistenceofathirdlevelofspatialrepresentation.Thislevel,typicallycalled“peripersonalspace”orthe“spaceofaction”playsacrucialroleinperception,especiallytouchandvisionforaction.Peripersonalspaceistheareaimmediatelysurroundingasubject’sbody,usuallydefinedastheareawhereinonecaneasilyreachandactivelyengage.Thesethreelevelsofspatialrepresentationaredistinct;theycanbedissociatedfromoneanotherandthereexistpathologiesthatleaveasubjectwithouttheabilitytorepresentonlyonelevelofrep-resentationthroughformsofspatialneglect(Mennemeieret a. l1992,Pegnaet al.2001).Thereisampleevidencethatitisrepresentationsin peripersonal space that mediate many of the tactual experiences(especiallytactualreference)thatI’vediscussedinthispaper.Tactualprojectionistypicallyaprojectionintoperipersonalspace;theuseoftactualmediatypicallyoccursinperipersonalspace.Inaddition,ithas
ThesamecriticismsdiscussedaboveapplytothisbodilyversionofMCT.Distaltouchexperiencesdonotrequireanexplicit,attended,orreferentiallygroundedexperienceofthebodyattheproximalpointsof contact.When I touchpaper throughapencil, Imayhavenoex-plicitawarenessofwhatishappeningtomyfingersasIexplorethepage.Whiletheremaybesomebackgroundexperienceofthebodyinsuchexperiences,wedonotexperiencedistalobjectsinvirtueofsuchproximalawarenessandcertainlynotviasomeexplicitinferencefromourbodilyexperiences.
7. Where Are Distal Touch Objects Located?
TheConnectionPrinciple constrains the referenceofour tactualex-periences.Butpossessingtheappropriateconnectionisnotthewholestory,forthereremainsanimportantquestionaboutthespatialchar-acterofdistaltouch.Inparticular,werequireanaccountofhowthetactual experience represents the distal objects as located some dis-tancefromthebody,giventhatourtactualreceptorsarealllocatedonthebody.InthissectionIwillarguethattactualobjectsarerepresent-edaslocatedinaspecialintermediatespatialframecommonlycalledperipersonal space. This space is defined by the limits of exploratoryreachandisthusanidealcandidatefordistaltouch.
17. O’Shaughnessymayhaveinmindsomethingweaker,likethecausalmedia-tionIdescribedabove.Ifso,thentheremaybenodisagreementbetweenourviews.However,heseemstosuggestthatweexperienceobjectsin virtue of bodilyawareness,whichistheviewI’marguingagainsthere.
strong role indetermining theextentofour immediatelyaccessibleenvironment.MohanMatthen(2005)hashighlightedtheimportanceof “motion-guiding vision”, and the relation between motor actionsandtheobjectsofourvisualexperience.Matthenarguesthatobjectscloseenoughforustointeractwithhaveaspecialphenomenalchar-acter,whathecallsa“feelingofpresence”.Theobjectsthatarecloseenoughforactiveengagement,thosewiththefeelingofpresence,areby theirnatures located inperipersonal space.Thecoordinatesandlocationsofobjectswillbesubject,notjusttothestructuresandlimitsofourreach,butalsototheinfluenceofmotion-guidingvision.Thereisthusastronginteractionbetweentouch(andcloselyrelatedactionslike reaching and grasping) and motion-guiding vision. A more de-tailedconsiderationofperipersonalspacewilloffermanyinsightsintothestructureofperceptualexperienceanditsspatialcharacter.
SusannaMillar(2008)hadsubjectssitinfrontofavisual-tangiblemapwithmarkedlandmarksforkeylocationssuchasthepostofficeorbank.Theirtaskwastomemorizethelocationsofthesekeypoints,usingeithervisionortouch,andthenperformalocationtaskontheblank map. They might be asked, for instance, to locate the bankonthemap. Inpreviousstudies, ithadbeenshownthat thereweremarkeddifferencesintaskperformancebetweensubjectswhousedtouchandthosewhousedvisiononthetask.Thissuggestedthatthetwosensesuseddifferent spatial frames.Millar showed that thisas-sumptionwasincorrectbyhavingeachgroupofsubjectsmakeuseofdifferentkindsofreferencecues.Subjectsusingvisionwereaskedtolocatelandmarksrelativetoegocentricframes(e. g.,alittletotherightofthebody’scenterline),whilesubjectsusingtouchwereinstructedtouseexternalreferencecues(coordinatemarkersonthesidesofthemap).WhatMillardiscoveredwasthatthetypeofreferencecuewasresponsiblefortaskdifferencesbetweentouchandvision.Subjectsus-ingvisionandegocentricreferencecuesperformedthesameastouchsubjectsinpreviousstudies;touchsubjectsusingexternalreferencecuesperformedthesameasvisionsubjectsinpreviousstudies.Thedifferencebetweenvisionandtouch,Millarargued,isnotadifference
Itisobviousthatvisualexperiencesrepresentobjectsandfeaturesinexternalspace.Itisalsoobviousthattouchrepresentsobjectsandfeatures in personal space. The error is thinking that these are theonly options. Both touch and vision seem able to represent objectsinperipersonalspace.Ithinkacarefulconsiderationofthenatureofperipersonal space allows us to explain how touch is able to repre-sentobjectsaslocatedinthespacearoundthebody.Thecoordinatesofperipersonalspacearedefined,afterall,bysuchthingsashowfarwe can step or reach in various directions, and these things, beinggrounded inproprioceptionandkinesthetic feedback,playacrucialrole ingenuinetactualexperiences.Thismightofferanexplanationforhowtactualprojectionworks(oneprojectsintothespacewhereonecan reach,manipulate,andsoonusinga toolor intermediary).Recallthatbyusingparticularexploratory procedures (EPs;again,thisterm is introduced by Lederman and Klatzky 1987) to investigateanobject,onecomestorepresentvariouselementsoftheobjectinperipersonalspace(byhowone’sgraspneedstochangetofeelacer-tainfeature,say).Tactualawarenessofcomplexorlargeobjectsmightrequiresomeimplicitawarenessthatmyarmneedstomovesuchandsuchadistancetoexplorethe farsideof theobject,etc.Andthesespatial facts can be grounded in the features of peripersonal spaceinsteadofexternalspace,whichmeanswenolongerneedtodefaulttobodyawarenesstoexplaintactualexperience.Whenwearehapti-callyengagedwiththethingsaroundus,thesethingsarealllocatedatspecificlocationsinperipersonalspace,andthefeaturesofthisspaceareavailableto(indeed,partiallyconstructedby)touch(cf.Kappers2007;KlatzkyandLederman2003b).
Theroleofperipersonalspacealsoallowsustohaveabetterun-derstandingoftherelationbetweentouchandtheothersenses.Thisisbecauseperipersonalspaceismultimodallyinfluencedbytheothersenses,especiallyvision.Action-guidingvision, for instance,playsa
importantroleinsecuringobjectreferenceandrecognitionintouchthan in vision. Touch is continually contrasted with vision, and thefocusislargelyonthefactthatbothsensesinvolvespatialrepresenta-tion(considerable focushasbeenontherepresentationofshape inbothsenses,forinstance).Itiseasytoassumethattouchandvisionmakesimilaruseofspatialinformationinsecuringreferenceandes-peciallyrecognition.Thisisnotthecase.Spatialinformationplaysasmallerroleintactualobject-recognitionthanitdoesinvision.Mostimportant in touch are so-called intensive features —things like mate-rialcomposition,texture,weight,temperature,andsoon.18Thismaytranslateovertoobjectreferenceaswell.Weseemtosecurereferencetothekeysinourpocketthroughintensivefeatureslikemetallicandcoldandsmall thanwedofromthespecificshapesoftheindividualkeys.Thisisactuallyasurprisingfact,butonewhichwasdiscoveredbycarefulempiricalinvestigation(Klatzkyet al.1993,LedermanandKlatzky 1997). Restricting the availability of so-called intensive cuescausesourotherwiseexcellenthapticrecognitionalcapacitiestosuffergreatly. For instance, Lederman and Klatzky (2003) found that sub-jectsgivenarangeoftangiblestimulishapedlikeordinaryobjects,butmadeoutofthesameuniformmaterial,findobject-identificationtasksmoredifficultthanwhentheyhaveaccesstothematerialcompositionand heft of the object but not its overall shape. Other studies haveshownthatnon-spatialsurfacepropertiesareavailablefasterinhap-ticprocessingthanarespatialfeatures(LedermanandKlatzky1997).This means that in a typical tactual experience we can be aware ofwhatsomethingis—wecanidentifytheobjectorarangeofitsmostsalientfeatures—withoutknowingwhereexactlythethingislocatedor its spatialcharacteristics.This facthelpsexplainhowonecanse-curetangiblereferencetoanobjectthroughaprobeorintermediaryevenwhenthatintermediarysuppliesonlylimitedspatialinformationabouttheobject(thatis,withoutspecifyingitsexactshapeandloca-tion).Thereferencecanbesecuredviasparsespatialinformationso
Ifthisiscorrect,thenthemainspatialdifferencebetweentouchandsight is a relative difference in the types of reference cues that eachtypically uses. Vision typically makes use of external reference cues,likeexternalobjectsor landmarksusedasanchors forassessingspa-tialrelationsbetweenobjects.Touch,ontheotherhand,typicallyusesbody-based reference cues, such as locations relative to the midlineof thetorsoorasmallmovementof thehandtothe left.Thediffer-entemphasisonthesetwotypesofcuesislargelyresponsiblefortheexperimental differences found between the senses. That is, repre-sentationsofexternalspacetypicallyinvolveexternalreferencecues,whereaspersonalspaceistypicallycenteredonbody-basedreferencecues.Becauseitmakesmoreconsistentuseofexternalreferencecues,visionseemstorepresentobjectsonlyinexternalspace(andviceversafortouchandbodilyspace).ButMillarshowedthatbyforcingsubjectstousebody-basedreferencecuesinvision(andexternalcuesintouch)subjects no longer displayed this striking differential data. Whenprompted,Millar found,subjectswereperfectlyabletouseexternalreferencecues intactualperceptionorbody-basedcues invision. Itturnsoutthatbothtypesofreferencecuecanbeinvokeddependingontaskdemandsandcontext.Thisdiscussionrevealsthattouchmostoftenattains spatial information relative tobody-basedcues,where-asvisiondoesnot.Thisaccounts for theassumptionthat thespatialcontent of touch involves only bodily coordinates. In the intermedi-aterange,however,bothkindsofcuescanbeinvoked,inbothvisionandtouch,toattainspatialinformationabouttheworld.Inotherwords,touchandvisionshareacommonspaceintheexternalenvironment.Thisspaceinvolvesexplicitrepresentationsofspatiallocationsintouchviareferencecuesthatarenotlocatedonthesurfaceofthebody.ThislevellinesuppreciselywithwhatI’vebeencallingperipersonalspace,wherebothtypesofcues—externalandbody-based—arepresent.
Anotheraspectoftouchthathasgonelargelyunnoticed(at leastamongphilosophers) isthefactthatspatial informationplaysa less
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anexcellentsetofcommentsthatimprovedthepaperincountlessways.Iam also thankful for useful questions received from audiences at the Uni-versityofToronto,theUniversityofBritishColumbia,andtheUniversityofMassachusetts,Boston.Finally,IwouldliketothankCaseyO’Callaghanforsuggestingthetitle.
longasthereisenoughadditionalinformationaboutanobject’sothersalientfeatures(solidity,roughness,weight,etc).Thecoordinatesofperipersonalspacearesparseinexactlythissense:theydonotspecifyexactlocationsorprecisegeometricrelations.Insteadtheylabelone’ssurroundingswithlimitedinformationabouttheimmediateenviron-mentinaction-guidingterms.Theseinturnallowasubjecttoengagewith a distal object via some appropriate intermediary and therebydiscoveritsdiagnostic,intensivefeatures.19
8. Conclusion
Iftheproceedingiscorrect,thenwecananddoexperienceobjectsthroughtouch,evenwhenthoseobjectsarenotincontactwiththeapparent limits of our bodies. And we can do so without explicitawareness of the proximal points of contact. Such experiences in-volveanappropriate informationalconnectionbetweenourbodiesand thedistal target.The linkage involves the reliable transmissionof tangible information, appropriate coordination with our explor-atory capacities, and the representation of coordinates supplied byour active engagement with the intermediate frame of peripersonalspace.Wepossessdistaltouch,notbybuildingupacomplexspatialrepresentationwithalltheobject’sfeatures,butbygroundingourrep-resentationsinsparse,easilyaccessiblefeatures,suchastextureandmaterial composition. This makes the referential character of touchimportantlydifferentfromthatofvisionandtheothersenses.Inaddi-tion,thisaccountofdistaltouchoughttobeofconsiderableinteresttothoseworkingonhapticinterfacesandvirtualrealitytechnologies. 20
20.Iamgrateful to the followingpeople forhelpfuldiscussionandquestionswhileworkingonthispaper:MohanMatthen,DianaRaffman,EvanThomp-son, Susanna Siegel, Kevin Connolly, Eric Margolis, Susan Lederman, JunLuo, Lana Kuhle, Adrienne Prettyman, Ranpal Dosanjh, Chris Mole, andMurat Aydede. Two anonymous referees for Philosopher’s Imprint provided
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