Karousou & López Ornat (2013). Prespeech Vocalizations and the Emergence of Speech

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Spanish Journal of Psychology(2013), 16, e32, 121. Universidad Complutense de Madrid and Colegio Ofcial de Psiclogos de Madriddoi:10.1017/sjp.2013.27

The nature and unction o in ants communicativeattempts prior to the emergence o language haverecently been in the spotlight o research or purposesranging rom support or theories o language devel-opment to the establishment o early indexes o devel-opmental disorders. Recent empirical results confrmthat in ants early vocal activity is not unrelated totheir subsequent linguistic development, as it wasonce thought (e.g., Jakobson, 1941/1968). Abundantevidence on the development o both ormal and

pragmatic properties o prespeech vocalizations 1 suggests their precursory character and central unctionin the emergence and development o language.Accordingly, transition into language seems rathergradual while early words seem to be built on the basiso knowledge and abilities progressively constructedduring the prespeech period o communicative devel-opment ( or reviews see McCune, 2008; Oller, 2000;Stoel-Gammon, 2011; Vihman, 1996; Vihman, DePaolis, &Keren-Portnoy, 2009).

More specifcally, recent research has identifedseveral early vocal precursors o speech, which aretaken to re ect in ants: (a) phonological development, both segmental and prosodic; (b) communicative devel-opment; and (c) early symbolic development. They allare thought to constitute prerequisite developments

or the emergence o language.

Prespeech Vocalizations and the Emergenceof Speech: A Study of 1005 Spanish Children

Alexandra Karousou 1 , and Susana Lpez-Ornat 2

1 Democritus University of Thrace (Greece)2 Universidad Complutense de Madrid (Spain)

Abstract. This study investigates 12 prespeech vocal behaviors which are taken to re ect childrens phonological, com-municative and early symbolic development. It explores their development (onset, duration and extinction) and theirrelation to early lexical development. A structured parental questionnaire on prespeech vocalizations was developed,validated and used or the evaluation o 1005 Spanish childrens early vocal development (830 months). In parallel, thesame childrens productive vocabulary was assessed using the vocabulary section o the European-Spanish MacArthur-Bates Communicative Development Inventories. Results highlight a global inverted U-shaped developmental patternwhich emerges rom the asynchronous development o the vocal behaviors examined, relating both their emergence andextinction to advances in linguistic development. Moreover, the protracted coexistence o prespeech vocalizations withearly speech and their signifcant correlations with vocabulary size reveal a gradual transition into language. Overall

results rein orce and extend previous fndings on the development o prespeech vocalizations and establish their rele-vance as early indexes o linguistic development. Finally, positive evidence on the use o an assisted parental reportmethod or reliably evaluating these developments is provided. Results are discussed within theoretical rameworksthat conceive language as the emergent product o complex developmental processes.

Received 20 May 2011; Revised 12 January 2012; Accepted 20 March 2012

Keywords: Prelinguistic/preverbal communication, early language development, emergence o speech, in ants andtoddlers, standardized assessment.

Correspondence concerning this article should be addressed toAlexandra Karousou, Democritus University o Thrace, Departmento Preschool Education Sciences, Nea Chili, 68100 Alexandroupoli,Greece.

Email: [email protected] or [email protected] work was supported by the Ministerio de Ciencia y Tecnologa,

Spain [grant number CICYT-PETRI: PTR1995-0412-OP], the UniversidadComplutense de Madrid [grant number GR58/08] and the SpanishMinisterio de Ciencia e Innovacin [grant number SEJ2007-67810]. We aregrate ul to all the Spanish amilies and to various pro essionals o earlydevelopment who collaborated in this study. Special thanks to PamelaSmith, an English riend, or her valuable help in avoiding linguistic andother errors. We also thank the anonymous reviewers o this paper ortheir use ul comments and substantial suggestions.

1We pre er the terms early or prespeech vocalizations, over thecommonly used prelinguistic vocalizations, assuming that transitioninto language is gradual and, thus, the distinction between linguisticand prelinguistic behaviors very problematic. In the same vein, ouruse o the term language (e.g., the emergence o language, transitioninto language, etc.) in its common acceptation o conventionallanguage must also be interpreted rom the standpoint o thisdevelopmental continuum, where prespeech vocalizations alreadyre ect many dimensions o linguistic knowledge and early languageis built upon many o the properties o prespeech vocalizations.


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2 A. Karousou and S. Lpez-Ornat

Early vocalizations as indexes of phonologicaldevelopment

The relation and continuity between prespeechvocalizations and early speech has been empiricallydocumented by numerous studies ocusing on the

ormal properties o early vocal activity. Recent

research has identifed phonological similarities between babbling and early words (e.g., McCune &Vihman, 2001; Vihman, Macken, Miller, Simmons, &Miller, 1985) and has highlighted the gradual adapta-tion o early vocalizations to the properties o words ina variety o languages (e.g., Boysson-Bardies & Vihman,1991). Cross-linguistic studies point to an in uence o the ambient language already in the prelinguistic period(e.g., Boysson-Bardies, Hall, Sagart, & Durand, 1989;Levitt & Wang, 1991), as opposed to purely innatepredispositions or language acquisition (e.g., Locke,1988). Moreover, both prespeech vocalizations and

early words are consistently reported to coexist in thevocal repertoire o in ants or several months, confrminga rather gradual transition into language (e.g., Elbers &Ton, 1985; Vihman et al., 1985). Finally, certain types o early vocal behaviors are ound to be prerequisites or anormative linguistic development, while qualitativeor quantitative aws are requently associated withsubsequent language disorders. For instance, theproduction o well- ormed, canonical syllables, o tenorganized in syllabic sequences -so called canonical babbling- is ound to precede normal lexical develop-ment (McCune & Vihman, 2001; Oller, 2000; Stoel-Gammon, 1992; Vihman, 1986).

Canonical babbling is argued to emerge at sometime between 4 and 10 months providing the childwith the necessary representations and resources orthe identifcation and shaping o early word orms(Stoel-Gammon, 2011; Vihman et al., 2009). At the beginning, childrens babbling typically consists o therepetition o a single syllable ( reduplicative babbling2), but gradually in ants manage to combine varyingarticulatory movements / syllables within the samevocalization ( variegated babbling). Moreover, the ageo onset o canonical babbling and the number o consonants produced consistently during childrens babble seem to be valid predictors o the onset o speech, the accuracy o speech production and lexicaldevelopment (e.g., McCathren, Yoder, & Warren, 1999;Menyuk, Liebergott, & Schultz, 1986; Vihman et al.,2009; Vihman & Greenlee, 1987). Finally, childrenwho present a delayed onset o canonical babbling(a ter the age o 10 months) are o ten reported to have

auditory problems and/or later linguistic delays oranomalies (e.g., Eilers & Oller, 1994; Lynch et al., 1995;Oller, Eilers, Neal, & Cobo-Lewis, 1998; Stark & Tallal,1988; Stoel-Gammon, 1989).

Regarding the suprasegmental properties o earlyvocalizations, it is widely acknowledged that prosodic

eatures such as intonation, duration and rhythm-also re ect a gradual in uence o the ambient language.More specifcally, there seems to be a consensus thatprosodic properties o the speech signal are bothperceived and produced be ore the production o speech-like segments (e.g., Boysson-Bardies, 1999;Crystal, 1986; Jusczyk, Cutler, & Redanz, 1993; Kent &Murray, 1982; Mehler et al., 1988; Nazzi, Bertoncini, &Mehler, 1988). For instance, traces o prosodic modula-tion were recently detected even in the spontaneouscry-vocalizations o newborn in ants, which seem to beshaped by the language they are exposed to prenatally(Mampe, Friederici, Christophe, & Wermke, 2009). Aswill be discussed in the next paragraph, various studiessuggest that these melodic or musical properties o thespeech signal are closely linked to the a ective unctionso early communication and to the subsequent abilityo in ants to express di erent communicative intentions.Thus, in the last quarter o the frst year, it looks as i di erent prosodic patterns become associated with theexpression o di erent communicative unctions or withdi erent communicative contexts, even though in somecases such association may be child-specifc (e.g.,Delack & Fowlow, 1978; DOdorico & Franco, 1991;Halliday, 1975; Papaeliou, Minadakis, & Cavouras, 2002).

Early vocalizations as indexes of communicativedevelopment

From the very frst months o li e, early vocalizationsare used by in ants as means o expressing their a ectivestates and needs (e.g., Malatesta, Culver, Tesman, &Shepard, 1989; Nadel & Muir, 2005; Papousek, 1992).In this early period, mother-in ant communication isheld by means other than lexical meaning, grammarand syntax (Malloch, Sharp, Campbell, Campbell, &Trevarthen, 1997, p. 495). Across cultures, the highlymelodious characteristics o in ant-directed speechand in ant-directed music (i.e., nursery songs andlullabies) provide power ul means or emotional trans-mission (e.g., Trainor, Austin, & Desjardins, 2000; vanPuyvelde et al., 2010) and communication o intentions(e.g., Fernald, 1989) or, in the words o Trevarthen(19992000), or the mother-in ant synrhythmic inter-action or attunement. In ants, rom very early, engage incommunications, characterized by rhythmic, melodicand bodily synchronization (communicative musi-cality; Malloch, 1999/2000; Malloch & Trevarthen,2008). According to this line o research, these early

2Vocal behaviors typed in italics in the Introduction, correspondto the vocal behaviors included in the Early Vocalizations Scale, theparental questionnaires used in the present study.


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Prespeech Vocalizations and the Emergence of Speech 3

communicative behaviors establish a setting o mutualunderstanding within which more advanced orms o communication are built. Around 2 months, in ants areknown to already engage actively in similar structuredcommunicative interchanges with their caregivers,characterized by rhythmic cycles o turn-taking, whichare o ten called proto-conversations (e.g., Bateson,1975; Ja e, Beebe, Feldstein, Crown, & Jasnow, 2001;Trevarthen & Aitken, 2001).

Imitation also seems to play a special part in theseearly emotional dialogues. It was recently documentedthat in ants not only imitate but also seek out andenjoy being imitated by adults (Kugiumutzakis,Kokkinaki, Markodimitraki, & Vitalaki, 2005; Nagy &Molnar, 2004). Thus, in ant imitation, involving bodymovements, vocalizations and acial expressions,appears to serve a communicative or social unction,through which in ants acquire in ormation aboutpeoples emotions, actions and intentions, but also a

cognitive/learning unction, through which in antsacquire new skills and knowledge about the world(e.g., Kugiumutzakis, 1999; Uzgiris, 1981). As ar asvocal imitation is concerned, babies as young as 2 to6 months old are ound capable o imitating mostlyvocalic, but also consonantal sounds (e.g., Kokkinaki &Kugiumutzakis, 2000; Kuhl & Meltzo , 1996). Moreover,in ants at 3 months regularly match their mothersvocalization pitch and requency intervals either inabsolute, or in relative terms (i.e., by repeating aninterval starting rom a di erent tone) (van Puyveldeet al., 2010) and also imitate its prosodic contour

(Gratier & Devouche, 2011; Papouek & Papouek, 1989).This early imitative activity is reported to accelerateduring the second year (Masur, 1993) and to includeimitation o words (e.g., Masur, 1995) and imitation o the prosodic patterns o larger units, such as entirephrases (Karousou, 2004). The importance o vocalimitative activity is highlighted by fndings showing,

or instance, a signifcant positive correlation betweenearly vocal or verbal imitation and later lexicaldevelopment (Masur & Eichorst, 2002; Masur, 1995;Rodgon & Kurdek, 1977; Snow, 1989). Additionally,de ects in vocal imitation have been reported to belinked with problems or delays in language devel-opment (Bishop, North, & Donlan, 1996; Sigman &Ungerer, 1984).

Although proto-conversations and early imitationsdo not seem to initially have an apparent goal or amaterial intentionality other than engaging a ectively,caregivers rom very early consistently interpret themand systematically produce contingent behaviors inresponse to particular types o in ant vocalizations(Goldstein & West, 1999; Gros-Louis, West, Goldstein, &King, 2006; Halliday, 1975; Hsu & Fogel, 2003). Thus,they gradually lead in ants to realize, around 5 months,

that their vocalizations can elicit reactions rom othersand, there ore, their vocalizing activity begins to acquirean instrumental value (Goldstein, Schwade, & Bornstein,2009). Well be ore the emergence o their frst words,in ants progressively use vocalizations in triadic com-municative settings (in ant-adult-object) as a meanso intentionally regulating the actions o their inter-locutor towards a concrete goal they wish to achieve.This is the case or the proto-imperativeor instrumentalvocalizations (e.g., Franco & Butterworth, 1996;Karousou, 2004), which appear around the age o 89 months and usually accompany relevant gestures,such as reaching towards an object that in ants wantto be given to them (e.g., Bates, Benigni, Bretherton,Camaioni, & Volterra, 1979; Bates, Camaioni, & Volterra,1975). Shortly a ter, another critical intentional behavioremerges: the frst proto-re erential use o vocalizations(e.g., Franco & Butterworth, 1996; Karousou, 2004), inthe sense o directing the attention o the communicative

partner to a specifc phenomenon, an interesting experi-ence that in ants want to share with him. Such vocal behaviors are o ten re erred to as deictic or proto-declarative vocalizations in analogy with the pointinggestures that usually accompany them (e.g., Bateset al., 1975, 1979; Capirci, Iverson, Pizzuto, & Volterra,1996; Caselli, 1983; Caselli & Volterra, 1990). Bates et al.(1979) described as proto- orms these early vocal andgestural means to express declarative and imperative

unctions and established a relationship between theiremergence and the development o language.

Apart rom their communicative use, early vocali-

zations have long been reported to also occur outsideo a social, communicative context, when in ants donot appear to have an intention to communicate withan interlocutor. The nature o this private use o prespeech vocalizations has recently begun to beexplored. For instance, signifcant di erences have been detected between the pitch patterns o vocalizationsuttered apparently with the intention to communicateand those related to solitary activities, in childrenaged 10 months (Papaeliou & Trevarthen, 2006) and1624 months (Fernndez Flecha, 2009). Moreover,it has been proposed that these private or solitaryprespeech vocalizations may share the cognitive unc-tions which are suggested or private speech (Diaz &Berk, 1992; Halliday, 1975; Vygotsky, 1934/1962) or, inother words, that they could be taken as an expressiono in ants internal mental activity, o cognitive orperceptual processing, planning or sel -regulation(see Winsler, Fernyhough, & Montero, 2009, or a recentreview). However, despite the growing consensusconcerning the cognitive unctions o private speech,the unctions and the exact developmental patternso private prespeech vocalizations have not yet beensystematically explored.


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( or urther details, see Method). Additionally, theexpressive vocabulary o the participant children wasassessed using the Vocabulary section o the European-Spanish MacArthur Communicative DevelopmentInventories (ES-CDIs) (Lpez Ornat et al., 2005).

Our decision to use a parental report method orevaluating the prespeech vocal development is sup-ported by previous fndings that suggest parentssensitivity in recognizing, consistently interpretingand validly reporting on various prespeech vocal behaviors (e.g., Harding, 1983; Meadows, Elias, &Bain, 2000; Oller, Eilers, & Basinger, 2001; Oller et al.,1998). Moreover, in recent years, various parentalreport assessment instruments have also includedsections on prespeech vocalizations and report posi-tively on the reliability o parents as in ormants o their childrens early vocal development (e.g., Grimm& Doil, 2000; Kishon-Rabin, Taitelbaum-Swead, Ezrati-Vinacour, Kronnenberg, & Hildesheimer, 2004; Lyytinen,

Poikkeus, Leiwo, Ahonen, & Lyytinen, 1996; Wetherby,Allen, Cleary, Kublin, & Goldstein, 2002). As or theactual scale used in this study, all possible precau-tions were taken during its construction, validationand administration in order to maximize its validityas a new measure on early vocalizations (see Method-Instrument & Procedure-). Finally, the MacArthur-Bates Communicative Development Inventories,whose European Spanish adaptation was used orthe evaluation o the participant childrens lexicaldevelopment, are repeatedly reported to constitutevalid measures or the assessment o productive

vocabulary (e.g., Dale, 1991; Dale, Bates, Reznick, &Morriset, 1989; Fenson et al., 2000; Jackson-Maldonado,Thal, Marchman, Bates, & Gutierrez-Clellen, 1993;Law & Roy, 2008; Ring & Fenson, 2000; Thal , Jackson-Maldonado, & Acosta, 2000).

Method

Participants

The sample consists o 1005 children (see Table 1) agedrom 8 to 30 months 3 (approx. 44 children per month

o age, 48.4% boys and 51.6% girls). An analysis o variance showed no e ect o gender on the score o the Early Vocalizations Scale, F(1, 1003) = .52, p > .05.All children were healthy, with no diagnosed sensory,physical or mental impairment. Furthermore, childrenat risk or language delay (i.e., children with prenatalor perinatal complications or premature low birth-weight< 2.200 kg) were also excluded rom the sample.

Many o the questionnaires were completed byamilies living in Madrid (44%) and the rest came romamilies all over Spain. Most questionnaires (88%)

were completed by the childrens mothers. The impacto parental education on the scores o the EarlyVocalizations Scale was ound non-signifcant (seeLpez Ornat et al., 2005).

For all 1005 children, Spanish (Castilian) was the mainlanguage spoken in their homes. Nonetheless, 21.95%o those children were reported to also have contactwith some other language. For 8.3% this exposure wasless than 5 hours per week (e.g., watching a DVD inEnglish, or occasionally visiting a Catalan speakingaunt, etc.). The remaining 13.6% o the sample ( N = 137)had a more regular contact with some other languageeither at home or outside. These data were not excluded

rom the analyses, as no signifcant e ect o the exposureto a second language was detected, neither on the totalscore o the Early Vocalizations Scale, t (1003) = .35

p > .05, nor on the scores o the individual vocal behav-iors studied, 2(2, N = 1005) 2.91, p > .05, in all cases.This result is consistent with previous research whichhas identifed only some qualitative di erences in thevocalizations o bilingual children (e.g., Maneva &Genesee 2002; but not in Poulin-Dubois & Goodz,2001), but no signifcant di erences in the age o onset,nor in quantitative measures o vocal per ormance(e.g., Oller, Eilers, Urbano, & Cobo-Lewis, 1997). Itis important to note that our data only re ect theoccurrence o broad vocal behaviors (we ask whetherthe children have produced these behaviors) and the

questions do not take account o any kind o qualitative/language-specifc properties o vocalizing activity(e.g., particular phonetic content, manner or place o articulation, concrete intonation contours, etc.). For allthose reasons, data o children exposed to a secondlanguage have not been excluded rom the presentanalyses.

Instruments

The Early Vocalizations Scale, a structured parentalquestionnaire on prespeech vocal behaviors, wasdeveloped, validated, standardized and used or theevaluation o the participant childrens early vocaldevelopment. Since it is a new measure, all possibleprecautions were taken in order to ensure the validityo the data collected. In a preliminary study ( N = 50)including both observational data (video-recordings)and interviews with caregivers, 16 candidate vocal behaviors were selected and their exact wording wasdecided according to parents ability to understandand retrieve rom memory the corresponding in orma-tion (Lpez Ornat et al., 2003). Subsequently, a rigorousconcurrent validity study empirically established the

3This age period is the one addressed by the original MacArthur-BatesCommunicative Development Inventories (Fenson et al., 1993) -theEuropean Spanish adaptation too-, spanning the period rom prespeechto speech production or most children.


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reliability o parents as in ormants o their childrensearly vocal development (Lpez Ornat et al., 2005).Direct measures o the spontaneous vocalizing activityo 60 children (830 months), video-recorded or 45minutes in three di erent everyday settings (play &personal care moments with parents and also whenalone) were compared to the scores o the parentalreports provided on the same day. An agreement between these measures (parental vs. observational)was calculated or each question. Results led to theelimination o two questions (on silent babblingand invented early words) which ailed to reach asatis actory parent-observer agreement. Furthermore,two additional questions (on rhythmic hand bangingand vocal expression o emotion) were excludedas, in a subsequent pilot study ( N = 96), they wereproven to have no discriminative value. Concordantly,the 12 questions fnally included in the standardizedversion o the Early Vocalizations Scale are the ones

or which parents were most reliable: parent-observeragreement > 85%, ( M = 89.8%, SD = 2.70). The parent-observer agreement rate or each vocal behavior isreported in Table 2. Moreover, this measure has a highdegree o internal consistency (Cronbachs alpha com-puted with each o the 12 items treated as an individualitem, = .874) and is highly reliable (Test-retest corre-lation: r(65) = .93).

A description o each o the 12 early vocal behaviorsincluded in the standardized Early Vocalizations Scalecan be ound in the second section o the Results. Asmentioned earlier, the wording o those questions wascare ully adapted to the parents ability to recognizethe corresponding vocal behaviors and included, wherepossible, an example o the vocalization or a description

o the everyday settings in which similar behaviors can be observed. For instance, the question on reduplicative babbling asks parents about syllables they can hearwell and which they could repeat, like pa-pa-pa orma-ma-ma, or the question on private vocalizationsspecifes the context in which similar vocalizationsare usually emitted (when children are alone in theircot / bed or on their playing mat).

Three possible answers/options were o ered toparents or each vocal behavior (a) Not yet answer:the vocal behavior has never been observed so ar,(b) Yes answer: the child is producing this vocal

Table 1. Distribution of the sample

(a) per age in months (b) per vocabulary size

Frequency Percent Frequency Percent

89 97 9.7 0 133 13.2

1011 85 8.5 001050 393 39.11213 110 10.9 051100 93 9.31415 120 11.9 101150 54 5.41617 78 7.8 151200 42 4.21819 77 7.7 201250 46 4.62021 77 7.7 251300 36 3.62223 68 6.8 301350 50 5.02425 90 9.0 351400 35 3.52627 83 8.3 401450 30 3.02829 79 7.9 451500 42 4.230 41 4.1 >500 51 5.1Total 1005 100 Total 1005 100

Table 2. Concurrent validity study results: Parent Observer rate of agreement for each vocal behavior included in the Early VocalizationsScale

Vocal behaviors Rate o Agreement

Reduplicative babbling 98.0%Variegated babbling 95.7%Proto-conversations 87.8%Proto-imperative

vocalizations90.2%

Proto-declarativevocalizations

89.5%

Word imitation 90.8%Prosody imitation 85.3%Private vocalizations

(Talking alone)85.2%

Private vocalizations(Talking to toys)

88.0%

Communicative intonation 85.4%Musical intonation 90.2%Early words 91.3%


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activity at this moment, and (c) No longer answer:the behavior has been observed in the past, but thechild no longer produces it. A ter its conclusion andgiven the results obtained, the Early VocalizationsScale was published as an optional Appendix sectionto the European Spanish version o the MacArthurCDIs [ES-CDIs] (Lpez Ornat et al., 2005) and includedin both its In ant Form (815 months) and its ToddlerForm (1630 months).

In parallel, or the assessment o the same childrensproductive vocabulary, the Vocabulary sections o theIn ant (815 months) and Toddler (1630 months)

orms o the ES-CDIs were used. As in all versions o the MacArthur-Bates CDIs, they are lengthy checklistso words, where parents are asked to mark the wordsthat their child uses. The In ant orm includes 303 wordsand the Toddler orm 588 words, organized in 20semantic-syntactic categories (e.g., social words, animals,

urniture, people, locations, actions, pronouns, prep-

ositions, quantifers, etc.). The score o productive vocab-ulary is calculated by adding-up the total number o words marked by parents. The ES-CDI Vocabularyscales have been ound to have a high degree o internalconsistency ( = .990) and be highly reliable (Test-retestcorrelation; In ant orm: r(25) = .987; Toddler orm:r(38) = .986). Finally, we should mention that thevocabulary section o the ES-CDI is ully adapted tothe particular linguistic, social and cultural charac-teristics o amilies living in Spain. At the same time,it is ully equivalent to all other versions o theMacArthur-CDIs, including the original US-English

CDI (Fenson et al., 1993) and the Mexican-Spanish CDI(Jackson-Maldonado et al., 2003).

Design

A cross-sectional design was used with two groupactors: (a) Age in Months with twelve equally

spaced intervals rom level 1 (89 months) to level 12(30 months), and (b) Productive Vocabulary Size withtwelve equally spaced intervals o 50 words, rom level1 (0 words) to level 12 (more than 500 words). Twelvevocal behaviors were measured using a structuredparental questionnaire.

Procedure

All questionnaires were handed out personally tocaregivers who were recruited through personalcontacts o the research group members, or throughpediatricians and local nursery schools. Once care-givers gave their in ormed consent to participate inthe study, they were o ered explicit instructions as tohow they should fll in the orm that corresponded totheir childs age. During the whole administration o both the Early Vocalizations Scale and the Vocabulary

checklists o the ES-CDIs, either a researcher, or achildhood pro essional (Pediatrician or Speech Therapist)or a trained Psychology student was present withthem, discussing any doubts or di fculties. We shouldnote that this procedure o assisted administration , di ers signifcantly rom the one requently used in thestandardization o other versions o the MacArthur-Bates CDIs (i.e., sending the Inventories by mail, with apaid mail response; e.g., Bates et al., 1994). This additionalmeasure was taken in order to minimize the possibilityo parents not understanding the questions in thequestionnaires and, thus, to enhance the validity o theparental reports. A ter the conclusion o the research,parents that wished to receive eedback on their childsper ormance received a personalized debriefng letter.

Results and Discussion

First section: General overview of early vocal

activityIn this section, we present the mean distribution o answers (Not yet, Yes, No longer) per age and pervocabulary size or the total 12 questions. In Figure 1,we observe that children produce prespeech vocal behaviors (Yes answers) during the entire develop-mental period studied. The Yes answer appears to be the prevailing answer or more than 60% o thequestions at all ages. Its characteristic inverted-Ushaped development is apparently due to certain vocal behaviors that are absent at the beginning o the study(Not yet answers), then appear during the middle agerange, and then gradually start disappearing a ter theage o 16 months (No longer answers). Moreover,in Figure 1 we observe that vocal behaviors keepemerging until the vocabulary size reaches 51100words where the Yes answers mark their highestrate (a mean o approx. 11 over 12 vocalizations arepresent). From that point on, as expressive lexicon

Figure 1. Mean distribution o Not yet, Yes, Nolonger answers (i) per age in months and (ii) per productivevocabulary size.


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increases, they gradually diminish to be replaced bythe No longer answers.

There ore, it seems that the development o someearly vocal behaviors ollows an inverted-U curve:they gradually emerge and are mostly produced be ore word production becomes established; thenthey gradually become marginal as, we assume, they become replaced by more advanced linguistic behav-iors. This fnding is empirically illustrated by a sig-nifcant positive correlation o the number o Nolonger answers with vocabulary size, rs(1003) = .74, p < .001 and also a negative correlation between thenumber o Not yet answers and vocabulary size,rs(1003) = .73, p < .001.

We should note, however, that even when vocabu-lary is quite developed, with more than 500 words inthe expressive lexicon o children, a mean o 6 (over 12)early vocal behaviors still remain present. We suspectthat, at this point, the rate o production o these vocal-

izations in the childrens vocal repertoires may be quitereduced and they may constitute rather occasionalor marginal behaviors. However, due to the act thatthe Early Vocalizations Scale does not provide anyquantitative in ormation on the production o those behaviors (they are rather all or nothing questions),this assumption cannot be empirically tested withthe present data. In any case, this result suggests that,even when word production is well established, earlyvocal behaviors do not disappear abruptly; instead,they coexist (marginally or not) with lexical productions

or quite a long time. We interpret this general result

as empirical support or the hypothesis o a gradual tran-sition into language held by non-nativist, emergentistapproaches on language development (e.g., Vihmanet al., 2009).

Second section: Development of individual vocalbehaviors

This section o Results and Discussion ocuses on thedevelopment o the 12 individual vocal behaviors thatcompose the Early Vocalizations Scale in order to obtaina more detailed account o early vocal development and be able to attribute the exact course o the above generaldevelopmental pattern. Descriptive requency analyseswere carried out to trace the development o each vocal behavior per age in months, as well as per vocabularysize. Moreover, McNemar tests or assessing the di er-ence between proportions o dependent/paired samples(herea ter Di erence Between Proportions or DBP)were per ormed in order to detect signifcant di erences between di erent developments. We should point outthat, due to the multiple comparisons per ormed, themost conservative signifcance level ( < .001) has beenadopted in the ollowing analyses.

We should note again, that the Vocalizations scaleo the ES-CDIs does not record the requency/rateo production o each vocal behavior within a childsvocal repertoire, but just its presence (or absence). Thus,the ollowing percentages re ect the proportion of chil-dren that do (or do not) produce these vocal behaviorsat each given developmental moment, independentlyo whether they do so regularly or just marginally.In other words, these results in orm us on the degree o generalization o each vocal behavior among (a) childreno the same age and (b) children with the same vocab-ulary size.

Finally, we should draw attention to the act thatthese results, by not presenting statistical means o thescores, but percentages o children that produce (or donot produce) each particular vocal behavior, directlyre ect the individual di erences registered in eachdevelopmental point: every percentage other than 0%or 100% implies an inter-participant variability o a

major (closer to 50%) or minor (closer to 0% or 100%)degree. Obviously, the exploration o the underlyingcauses o these individual di erences is a very complexempirical problem, which exceeds the scope o thiswork. In words o Bates et al. (1994), individual di er-ences in early language development o ten re ect acomplex interplay o developmental and stylisticvariation (p.119). Their disentanglement, thus, willnot be addressed in this paper.

Babbling

wo questions on babbling are included in theEarly Vocalizations Scale, which both capture a seg-mental dimension o early vocalizing activity: one onreduplicative babbling in which parents report onwhether their children repeat a well- ormed syllableseveral or many times, and one on variegated babbling,in which parents are asked whether their childrencombine syllables which are not all the same. Figure 2represents the developmental patterns or these twotypes o babbling.

Almost all parents (> 90%) report that reduplicativebabbling is already present at 89 months or when theirchildren have not yet produced any words. In thesubsequent months (1015 months) reduplicative babbling urther increases, reaching approximatelya 100% o the sample. In contrast, variegated babbling is produced by a signifcantly lower percentage o children (7090%) in the earlier stages (DBP signifcant[ p < .001] rom 8 to 17 months or rom 0 to 50 words).In line with previous studies on babbling, this resultprobably re ects childrens di fculty in combiningvarying articulatory movements within the samevocalization, or, in words o Vihman et al. (2009:119),to gain control over the content within each syllable.


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Both types o babbling, a ter 18 months or a ter theproduction o 100 words, ollow a similar developmentalpattern: as vocabulary grows, the percentage o childrenthat are reported to babble slowly diminishes. In thedevelopmental periods between 2227 months or between 100350 words, we see the highest degree o

individual di erences: while an important percentageo children are reported to have ceased their babblingactivity, some others seem to continue babbling. Finally,when productive vocabulary reaches > 500 words, thepercentage o the latter has dropped to less than 10%while approximately 90% o the children are reportedto no longer babble.

This result rein orces the gradual transition intolanguage hypothesis, by showing that earlier ormso vocal communication do not disappear abruptly,even when word production is established. It isconsistent with previous observational results report-ing that babbling production continues to coexistwith frst words or several months and, also, thatchildren vary in their use o babble a ter they have begun to produce words (Vihman et al., 1985; Vihman& Miller, 1988). Nonetheless, the exact extent o thisco-existence has never been reported until nowsince, to our knowledge, no study has explicitlylooked or babbling in older children who alreadyproduce quite a ew words. The causes o the above-mentioned individual di erences would need urtherexploration, as they could be due not only to devel-opmental, but also to stylistic di erences among

children, or even to di erences in their parents reportingon these behaviors.

Proto-functions

Childrens communicative development is captured by three questions on the unctions o early vocal

activity, namely: a question on Proto-conversations, inwhich parents report on whether, when they talk totheir children, the latter seem to reply and take-turns, a question on Proto-imperative vocalizations,in which parents are asked whether their childrenvocalize to request di erent things, and one on Proto-declarative vocalizations, in which they report on theirchildrens use o vocal means to call their attention toa particular object or event they are interested in.Figure 3 represents the developmental patterns o thesethree proto- unctions.

The three developments show a certain similarity;they are all o relatively early emergence, as > 70%o children are reported to produce them at 8 months

Figure 2. BABBLING: Percentage o children per answer(Not yet, Yes, No longer) (i) per age in months and (ii) pervocabulary size.

Figure 3. PROTO-FUNCTIONS: Percentage o children peranswer (Not yet, Yes, No longer) (i) per age in months and(ii) per vocabulary size.


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or when they have not yet produced any word, theyare all massively present (> 90% o the children) by1213 months or by the time 150 words are produced,and then they gradually all decrease. Nonetheless,there are also interesting di erences in their rates thatare worth considering. In particular, in line with researchsuggesting an early emergence o protoconversations,it seems that the earliest or most common communica-tive use o early vocalizations at 89 months takesplace in a (proto) conversational context or 87.6% o the children. Interestingly, these turn-taking inter-changes with no lexical content are the ones that by30 months or by > 500 words show the minor reduction(DBP signifcant [ p < .001] a ter 200 words againstproto-imperative, and rom 200 to 350 words, & in> 500 words against proto-declarative vocalizations).Around 2425 months, or when children have produced400 words, there is an important drop in their rate but,even when vocabulary size grows to > 500 words, they

are still produced by hal o the sample. Given that theparticular question addressed to parents does notspeci y the orm o these early dialogues, nor as weexplained earlier, does it record their requency/rate o production, this perhaps re ects the act that non-wordvocalizations are sporadically used as a conversationaltool even later, or even through adulthood (e.g., thephatic unction o expressions like hmm, ha).

Proto-imperative and proto-declarative vocalizations,in turn, reach a rate o > 90% at 1011 months and1213 months respectively. Proto-imperatives are alsoearlier than proto-declaratives, when vocabulary size

is taken into account: the frst reach their highest ratewhen 150 words are produced, while the latter in the51100 words interval (DBP signifcant [ p < .001] in 150words and also at 1011 months). These results, byshowing an earlier development o proto-imperativesin relation to proto-declaratives, are consistent withprevious fndings on early vocal communicative devel-opment (Karousou, 2004) and on the emergence o relevant communicative gestures (e.g., Bates et al.,1979). A ter 1517 months both behaviors record animportant drop in their developmental curve and, bythe time expressive lexicon reaches > 500 words, theyhave gradually reduced their presence to only 20 or30% o the sample respectively. This fnding would be again consistent with the normal substitution-by-language process. In other words, as children developlexical means or expressing their requests and orre erring to the world, the presence o those earlycommunicative resources drops. The explanation o the protracted co-existence o both proto- unctionswith conventional speech could be related again tothe act that present data do not re ect possible quan-titative variations in the production o vocal behaviors.Thus, as a vocabulary o 200, 300 or even the maximum

o 588 words would certainly not permit a child toexpress every intended request and re erence by lexicalmeans, it is to be expected that occasionally she could

all back on more primitive ways o communication.Nonetheless, the exact causes o the important indi-vidual di erences noted again, especially a ter theproduction o the frst 200 words, should be the objecto urther exploration.

Private vocalizations

The Early Vocalizations Scale contains two questionson private or non-communicative vocalizations: onewhich is addressed to no one and nothing and could be considered as a orm o thinking aloud ( talking alone or talking to oneself ) and the other, which accompaniesexploratory activities on inanimate objects ( talking totoys). Figure 4 re ects the developmental patterns o these two vocal behaviors that apparently do not serve

any direct communicative goal.The developmental pattern o the talking alone / to

onesel vocal behavior has been the only one, amongthe 12 behaviors studied, whose presence remainsrelatively stable or approximately 9095% o the par-ticipant children throughout the entire developmentalperiod under consideration. Only when plotted againstvocabulary size can we observe a small percentage o children (approx. 20%) with a productive vocabulary o > 500 words who are reported to no longer producethese activities.

Figure 4. PRIVATE VOCALIZATIONS: Percentage o children per answer (Not yet, Yes, No longer) (i) per age inmonths and (ii) per vocabulary size.


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This contrasts slightly with the other type o non-communicative vocal behavior, which accompanies themanipulation or exploration o an object. This explor-atory type o vocal activity shows a later development.In particular, in the 89 months interval or whenchildren have not yet produced any words, it is pro-duced by 62% o the sample. At 1213 months its ratereaches 81.8% and only a ter the age o 25 months orwhen the vocabulary size grows to > 100 words, doesthe percentage o children that engage in similar activ-ities exceed 90% o the sample. Accordingly, the DBPanalysis reveals that these two measures o privatespeech ollow a signifcantly di erent development( p < .001) throughout the 8 to 19 months interval or theinterval between 050 words, and only during thesubsequent stages do their paths converge. Sincevocalizing during the manipulation o an inanimateobject could be, at times, re ecting a more symbolicactivity (e.g., pretend play), we speculate that this

developmental lag might be partially a ected by thedevelopment o similar early representational abilities(McCune, 1995).

The constant and robust percentage o solitaryvocalizations does not address orm stability acrossdevelopment, as the questions included in the ES-CDIsdo not speci y the orm o these vocal behaviors. Wesuppose that their orms change and develop acrossthe 8 to 30 month span in interesting ways which, as

ar as we know, are unknown in our feld. The act thatthese early vocal behaviors remain so requent even at30 months tempts to relate them to a stable mechanism,

possibly re ecting internal perceptual and cognitiveprocessing. In that sense, private prespeechvocalizationscould constitute the precursors o private speech,

ulflling a learning or sel -regulatory unction (e.g.,Diaz & Berk, 1992; Goldstein, Schwade, Briesch, &Syal, 2010; Papouek & Papouek, 1981; Vygotsky,1934/1962; Winsler, 2009).

Melodic vocalizations.

The development o childrens ability to manipulatemelodic contours (musical or linguistic) is captured bytwo questions: one in which parents report on whethertheir children sing, perhaps a ter having heard anadult or some doll singing, and one in which they areasked whether their children engage speaking with-out words and it seems as i they asked a question, theyhave been surprised, etc. Figure 5 represents the inter-esting development o these two vocal behaviors.

The two curves show a remarkable initial paralleland simultaneous development, starting at a rate o 5055% o the sample and growing to 8590% by theages o 2021 months or by the time vocabulary reaches150200 words (DBP non-signifcant). Interestingly,

this development bi urcates at 2223 months or at 200words, separating singing rom using prosody inorder to communicate (DBP signifcant [ p < .001] rom24 to 30 months and rom 251300 to > 500 words).At that point, the proportion o children that use prosody(without lexical content) in order to communicate

diminishes. We assume these vocalizations gradually become replaced by ull linguistic productions, wherecommunication is accomplished not only throughprosodic modulations, but also through words. Theuse o singing however does not decline; it remainspresent in more than 90% o the children at the endo the developmental period studied.

These fndings are consistent with results suggestingthat childrens frst singing attempts are produced ataround 12 months and, at 18 months, children startgenerating recognizable songs (e.g., Ostwald, 1973;

or reviews, see Dowling, 1999). Moreover, and perhapsmore interestingly, the remarkable initial simultaneousdevelopment o the two behaviors is consistent withthe view o an early ontogenetic relation betweenmusic and language. As explained in more detail inthe Introduction, music is considered by variousresearchers as one o the earliest means o mother-in ant communication. Across cultures, parents attractand maintain the attention o in ants through theexaggerated melody o the in ant-directed speechand through the melody o in ant-directed music(e.g., Nakata & Trehub, 2004; Shenfeld, Trehub, &Nakata, 2003). In ants actively reply by synchronizing

Figure 5. MELODIC VOCALIZATIONS: Percentage o children per answer (Not yet, Yes, No longer) (i) per age inmonths and (ii) per vocabulary size.


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to their parents vocalizations rhythm, melody, har-mony and movements (e.g., Malloch & Trevarthen,2008). According to this line o research, these commu-nications constitute a musical proto-language that setsup the emotional and communicative oundations

or uture orms o communication. In a recent research,van Puyvelde et al. (2010) by conducting a detailedtonal analysis o both in ant directed speech and in antvocalizations ound that they all share with music thesame universal tonal basic aspects (harmonics). In thesame vein, many scientists suggest that precursorso early speech are initially indiscriminable romprecursors o spontaneous singing, and that earlyvocalizations can be regarded both as prespeech andas premusical behaviors (e.g., Chen-Ha teck, 1997;Papouek, 1996). In words o Papouek (1996, p. 104):Preverbal communication may represent a commonontogenetic avenue along which two highly structuredand exclusively human capacities develop: speech and

singing. It is suggested that, only later, when childrenstart to develop specialized language processing(Elman et al., 1996) and to fne-tune to culture-specifcaspects o music (25 years; see Hannon & Trainor,2007, or a review), these two behaviors become moredi erentiated. Present results point to the end o thesecond year, or when children have produced 250di erent words, as possible candidate moments orthis divergence.

Vocal imitation

Two questions on spontaneous vocal imitation areincluded in the Early Vocalizations Scale, namely: oneon imitation o the suprasegmental properties o speech, where parents report on whether their childrentry to reproduce the intonation / melody o a sentencethey just heard (e.g., a question) and one, mostly pointingat imitation o the segmental content o speech, inwhich parents report on whether their children tryto repeat a word they just heard. Figure 6 representsthe developmental patterns o those two types o vocal imitation.

On the whole, word imitation appears to developearlier and reach a higher rate than imitation o sentencecontours. More specifcally, word imitation is produced by approximately 30% o the sample at 89 months orwhen no word is yet produced and develops to reacha rate o > 90% at 2021 months or when 51100 wordsare produced. Imitation o intonation, in turn, startsonly marginally (1112%) and develops gradually toreach its highest percentage (approx. 90% o children)at the 2627 months or 251300 words interval.

This result suggests that, although the ability toimitate prosodic contours appears to emerge early in thefrst year o li e, during mother-in ant communication

o emotions (e.g., Gratier & Devouche, 2011; Papouek &Papouek, 1989), prosodic imitation o large linguisticunits (i.e., entire phrases) ulflling a more concretepragmatic unction (e.g., a question) seems to appearlater. This relative delay is also in line with previousstudies showing a di fculty in accurately imitatingprosodic contours o linguistic phrases at 12 months

(Schaerlaekens, Forrez , & Van Bael, 1990; Siegel, Cooper,Morgan, & Brenneise-Sarshad, 1990) while around 3or 4 years this ability seems already quite developed(Loeb & Allen, 1993; Snow, 2001). Furthermore, thedi erence between these two developments (DBPsignifcant, p < .001 rom 8 to 24 months, and rom 0 to151200 words) could re ect the existence o di erentunderlying processing mechanisms: mostly segmental analytic, in the case o word imitation, and mostlyprosodic holistic, in the case o imitation o wholesentence contours. These two processing types have been previously suggested by other researchers asdi erent but complementary strategies o languagelearning (Peters, 1977; 1983).

Nonetheless, there are also interesting similaritiesin the two developments. When vocabulary size istaken into consideration, both imitative behaviorsproduce a most remarkable rise o approximately 80%in the period between the production o the very frstword and the production o 100 words. It appears as i an imitative mechanism is tied to the production o the frst 100 words or 80% o those children. Then bothimitative behaviors remain quite requent indicating ahigh unctionality o imitative behavior throughout

Figure 6. VOCAL IMITATION: Percentage o children peranswer (Not yet, Yes, No longer) (i) per age in months and(ii) per vocabulary size.


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the entire period studied and rein orcing previousfndings on the relation between imitation o wordsand vocabulary size in the early phases o lexicaldevelopment (e.g., Masur & Eichorst, 2002). Only atthe end o this period do we detect a very moderatedecline, which is due to a relatively small percentage

o children (12.2% and 19.5% respectively) who arereported to no longer exhibit these imitative behaviors.

Early words

The ability o children to produce their early and stillimmature representational vocalizations is captured by a quest ion on early words. It asks whether thechildren produce words which sound a bit like realones, but only the parents can understand immediately.Figure 7 represents the developmental pattern o thesevocalizations.

The development o early words is characterized by a curve o an inverted-U shape re ecting the tempo-rary character o those immature early words. Morespecifcally, early words during the 89 month intervalare scarce and produced by a small percentage o children (16.5%). This rate grows quite rapidly to reach80% at 1415 months, and exceeds 90% during the1823 months interval. Then, during the last months o the period studied, early words decline to be producedat 30 months by a 61% o the sample. Moreover, whenthe number o words produced is taken into account,some parents (11.28%) report that their children

already produce early words when no real wordsare yet reported in the Vocabulary section. This pro-portion, then, rises very quickly to reach a ull 100%in the 51100 words interval, and remains practicallystable until children have produced 250 di erentwords. Then the production o early words graduallydeclines to be produced by only 40% o the samplewhen vocabulary grows to > 500 words.

Overall, results suggest that, a ter 23 months or a ter250 words, early words are gradually being replaced by words with a tighter match to the sound re erentpair o the model language, as suggested by previousresearch (e.g., Vihman et al., 2009). As mentioned be ore, Vihman and McCune (1994) described as theragged beginnings o word use the developmentalperiod where children produce vocalizations o varyingdegrees o wordiness. According to the results wepresent, this period seems to be o considerable length,since it covers the age span rom 14 to 23 months ormore than 80% o the children studied and extends beyond 29 months or 60% o them.

Third Section: Continuity of the Early VocalizationsScale and correlations with Vocabulary

As discussed in the previous section o Results &Discussion, some o the vocal behaviors studied are

abundant only temporarily. A ter a certain point o development, and especially as word productionadvances, their use gradually becomes less requentamong children. Moreover, in the frst section o theresults, it has been shown that this inverted-U shapeddevelopmental pattern o early vocalizations is relatedto vocabulary growth process.

Accordingly, in this third section o Results andDiscussion, in order to calculate the total score or theEarly Vocalizations Scale, we assigned the ollowingvalues to the three possible options o ered to parents:

Not yet answer = 0, Yes answer = 1, No longer answer = 2

Note that, although both Not yet and No longeroptions imply an absence o each behavior, this scoringhas been adopted in the ollowing group o analysesso as to re ect the developmental value o the threeoptions.

In Figure 8 we examine the development o themean total scores (and their respective standard devi-ations) in the Early Vocalizations Section (a) per agein months and (b) per vocabulary size.

These results illustrate a remarkable continuity o the Early Vocalizations Scale in measuring childrensvocal development or all ages covered by both In ant(815 months) and Toddler (1630 months) orms o the ES-CDIs. An analysis o variance urther demon-strates the highly signifcant e ect that age has onthe total scores in the Vocalizations scale, F(22, 982) =59.100, p < .001. A Bon erroni post-hoc test (signifcancelevel = .001) showed that all ages produce a signifcantvariation to the total score, when compared to ages4 to 7 months younger or older. Additionally, aTukey Honestly Signifcant Di erence post-hoc test

Figure 7. EARLY WORDS: Percentage o children peranswer (Not yet, Yes, No longer) (i) per age in months and(ii) per vocabulary size.


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(signifcance level = .001) grouped ages (in months)to the ollowing homogeneous subsets: 812, 1015,1117, 1319, 1421, 1924, 2126, 2430 months. Theseresults confrm the continuity o this new scale andpoint to a gradual, slow and overlapping development.

Furthermore, and most interestingly, results revealan important relation between the total scores in theEarly Vocalizations Scale and the size o ProductiveVocabulary. This relation is statistically illustrated bya high correlation between these two measures o communicative development, rs (1003) = .845, p < .001.Moreover, table 3 presents the correlations between

each individual vocal behavior and the participantsvocabulary size, arranged in descending order.

In general, all vocal behaviors, as measured by theEarly Vocalizations Scale, were signifcantly correlated( p < .001) with the total scores in Productive Vocabulary(i.e., the number o words children produce), confrmingthe relevance o those early behaviors in evaluatingin ants and toddlers linguistic development. Takinginto account the previous results, this signifcance isquite high or vocal behaviors that present the invertedU-shaped development not yet yes no longer(scored as 012, in this group o analyses) such as

early words, variegated and canonical babbling. Bothtypes o imitation, as well as proto-imperative andproto-declarative vocalizations, also predict a con-siderable amount o the variation in vocabulary size.Nonetheless, as expected, the vocal behaviors whichdo not tend to reduce their presence over time andrather have a stable development during the last months,or even throughout the whole developmental period,such as singing, proto-conversations, talking aloneand talking to toys, only predict a very low amount o variation in vocabulary.

We should, however, point out that when all theseindividual behaviors, with a higher or lower individualcorrelation to vocabulary, are combined in a scale witha high degree o internal consistency, as the EarlyVocalizations Scale, the resulting amount o predictionis defnitely enhanced (in this case, rs(1003) = .845, p < .001, see above).

On the whole, the present results extend previousfndings on the relation between babbling and lexicaldevelopment (see Stoel-Gammon, 2011; Vihman et al.,2009) and between word imitation and lexical develop-ment (e.g., Masur & Eichorst 2002) by adding inter-esting results about the signifcant relation o all vocal behaviors studied with the growth in the size o vocab-ulary produced by in ants and toddlers. The practicalimportance o these fndings lies in the possibility thatthe Early Vocalizations Scale o ers or an early andconcise screening o communicative development o children aged 8 to 30 months. On the theoretical side,they constitute additional evidence on the relationship between prespeech vocalizat ions and lexical devel-opment, as well as on the interpretation o prespeechvocalizations as precursors o speech.

General Discussion

The present study investigated the development o 12 di erent prespeech vocal behaviors in a quite largesample o Spanish children ( N = 1005) covering all ages

rom 8 to 30 months. Our main aim was to analyze in

Figure 8. Mean scores (with standard deviations) in EarlyVocalizations Scale (i) per age in months and (ii) pervocabulary size. Note: Scoring o the scale: sum o the 12vocal behaviors scores. For every Not yet answer 0 points,

or every Yes answer +1 point, or every No longer answer+2 points.

Table 3. Correlatons (Spearmans rho): Individual early vocalbehaviors * Vocabulary size

Vocal behaviors Productive Vocabulary

Early words .725**Variegated babbling .645**

Reduplicative babbling .634**Imitation o intonation .622**Word imitation .582**Proto-imperative

vocalizations.579**

Proto-declarativevocalizations

.521**

Communicativeintonation

.502**

Musical intonation(singing)

.400**

Proto-conversations .396**Private vocalizations

(talking to toys)

.338**

Private vocalizations(talking alone)

.231**

Note: **Correlation is signi cant at level .001 (2tailed).


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detail their developmental patterns and their relationwith the same childrens early lexical development.Our expectation was that, by collecting data rom aconsiderable number o children selected to representquite an extended developmental period, we couldprovide an integrative view o early vocal and lexicaldevelopment and, thus, fll in some o the existing gapsin the currently ragmented landscape o prespeechvocal communication.

Due to the overwhelming methodological complexitythat an observational study or such an extensivenumber o participants would entail (e.g., exceptionallytime-consuming data collection, transcription, codingand analysis o many dimensions o the relevant data),we opted or an assisted parental report methodology.In particular, a ter having ensured that parents couldprovide reliable data on a variety o dimensions o prespeech vocal development, we adopted the use o anew structured questionnaire, the Early Vocalizations

Scale. Given the results presented in this paper, thisscale has been published as an optional Appendixsection in the European-Spanish version o the MacArthurCDIs.

Naturally, this methodological option is not reeo disadvantages. The in ormation one can obtainthrough parental reports is necessarily limited to thedimensions o vocal activity that the particular scalesmeasure and always depends on the wording o theparticular questions which, in turn, are constrained bythe in ormation parents can provide in a reliable way.We assume this limitation is an unavoidable trade-o

between the number o participants and the ormaldetail o a study. As explained in detail in the Methodsection, the vocal behaviors included in the ques-tionnaire, as well as their wording, are the result o various studies and analyses (observational study,parent interviews, concurrent validity study, pilotstudy, etc.) which empirically established the reliabilityand the validity o the scale.

Another constraint is that the data collected usingthe Early Vocalizations Scale do not provide anyquantitative in ormation on the production o eachvocal behavior. They just record the presence orabsence o each vocalizing type in a childs vocalrepertoire, independently o its rate or requency o production. Consequently, as pointed out earlier, theresults we presented are not sensitive to possiblechanges in the proportions among di erent vocal behav-iors along developmental change (e.g., rom producingabundant variegated babbling and scarce early words,to the opposite).

However, we believe the results we obtained areinteresting in several ways. Currently, all vocal behav-iors studied are considered precursors o speech, andmany o them, i not all, have been established as

prerequisites or normative linguistic development.This parental report study included, there ore, itemson the best known phonological (segmental and pro-sodic), communicative, and early symbolic develop-ments. But it also provided questions on behaviorswhich are taken to express important learning mecha-nisms or language, such as the imitative and privatevocalizations. Several though not all- o these behav-iors have already been the object o extensive observa-tional research, but still, the span, timing, and patterno their development has not been ully defned. Forinstance, one o the most extensively studied prespeechvocal behavior is canonical babbling. In the literature,one may fnd many results on its nature and orm (e.g.,Oller, 2000; Vihman, 1986), on its relation to frst words(e.g., McCune & Vihman, 2001), on its age o onset(e.g., Oller at al., 1999) and on its coexistence with frstwords (e.g., Elbers & Ton, 1985; Vihman et al., 1985).However, the present study has both rein orced pre-

vious fndings with results on a large sample o children,and expanded them with in ormation on the subse-quent course o these vocal activities. For instance, itis ound that some ( ew) children continue babblingeven when they have produced quite a ew words,that variegated babbling appears to coexist with earlywords or approximately 12 months or more than 70%o the population studied, and that early immaturewords are produced or a whole year or more than80% o the sample. We believe that these fndingsconstitute interesting expansions o previous resultswhich reported, but never detailed, the coexistence o

prespeech vocalizations with early language and theimportant individual di erences that characterize thoseearly, transitory phases o vocal development.

Furthermore, the results on the developmentalpatterns o less studied vocal behaviors provide newevidence o the complexity o early vocal and commu-nicative development, and shed light on the emergenceo language out o various preceding abilities o varying nature. Thus, although the development o early communicative unctions has been widely studiedthrough the analysis o in ant gestures (e.g., Bates et al.,1975, 1979; Capirci et al., 1996), to our knowledge,these results have not been corroborated with exten-sive data on early vocal communication. Accordingto present results, children appear to use non-wordvocalizations as a means or communicating since veryearly. In line with research on early protoconversa-tions (e.g., Trevarthen & Aitken, 2001), during theearliest months o the study prespeech vocalizationsare massively produced in turn-taking settings, duringparent-in ant communicative interchanges. Aroundthe age o 1011 months, the majority o children alsostart producing vocalizations with an instrumentalvalue and two months later they start producing them


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in a proto-re erential context, in an attempt to sharetheir experiences and states with their communicativepartners. The emergence o these early communicative

unctions has long been considered an importantprecursor o the emergence o lexical re erence (e.g.,Bates et al., 1979). Concordantly, these non-wordvocalizations appear to gradually reduce their pres-ence, as children manage to produce vocalizationswith a tighter match to the conventional sound-re erentpair o the ambient language or, in other words, as theydevelop lexical means to re er to the world.

However, in parallel with the communicative use o vocalizations, the vast major ity o children also seemto vocalize when they are alone, when they appear tohave no intention to communicate with an interlocutor.This private use o vocalizations, interestingly, appearsto be a robust and consistent behavior throughout theentire developmental period studied. In line withresearch on subsequent private speech (e.g., Winsler

et al., 2009), this result points to the interpretation o private vocalizations as related to a stable learningmechanism or even as a sel -regulating tool or cogni-tive or perceptual processing.

Imitation, also, seems to play an important role inlexical development, since the emergence o childrensfrst words appears to be linked to their ability to imitate both the segmental content o speech and its melodiccontour. The subsequent high unctionality o theseimitative vocalizations rein orces the assumption thatvocal imitation constitutes an important mechanismwhich acilitates lexical development (e.g., Masur, 1995).

Finally, the analysis o data on the melodic propertieso early vocalizations showed that the vast majority o children, by their frst birthday, appear to have devel-oped the ability to modulate melodic contours in orderto convey specifc meanings (e.g., ask a question, showsurprise or scold someone) but also in order to sing a

amiliar song. The development o these two melodicvocal behaviors shows a remarkable initial paralleldevelopment, and only at 24 months or when 250 wordsare produced do their developmental paths signifcantlydiverge: the vast majority o children keep singing,while communicative use o intonation (without lexicalcontent) diminishes to be, presumably, integrated toproductions with lexical content. These results rein-

orce the view o an early ontogenetic relation betweenmusic and language (e.g., Malloch & Trevarthen, 2008;Papouek, 1996) and support the role o communicativemusicality in childrens early linguistic development.

The relevance o all the prespeech vocal behaviorsstudied to the development o language is urtherenhanced by the high correlation o the overall scorein Early Vocalizations with lexical development, butalso by strong correlations o the individual vocal behaviors studied with vocabulary size.

In summary, the general picture o early vocal devel-opment appears to be the result o various asynchro-nous and overlapping developments which re ect theunderlying expansion and fne-tuning o a variety o

acets o linguistic knowledge (segmental, prosodic,communicative, symbolic/representational). We inter-pret all these parallel developments as di erent, thoughinteracting, pathways through which the learningsystem gets in shape or language learning. Prespeechvocal activity seems to provide the toddler with a kito elementary but e fcient tools or its language devel-opment process: tools or identi ying, segmenting andarticulating linguistic structures, whether holistic ordiscrete; or e fciently hypothesizing linguistic unctionsand mapping them onto distinct orms; or imitatingany sort o input ragment, whether segmental orsuprasegmental; or engaging in linguistic interactionwith others, and also or using language as a tool orthinking and exploring the world.

Overall, we suggest that the tracing o these devel-opmental patterns, as well as their signifcant rela-tion with childrens early lexical development,constitute new evidence on the developmental con-tinuity o the language learning process. We wouldargue that these results do support theoretical ap-proaches that conceive language as the emergentproduct o various interacting developments pro-gressively constructed during the prespeech periodo communicative development (e.g., Elman et al.,1996; Thelen & Smith, 1994; Vihman et al., 2009). Onthe practical side, the present results establish the

relevance o all prespeech vocal behaviors studiedor an early evaluation o communicative develop-ment, but also the potential or using assisted paren-tal report methods to obtain valid and reliable dataon these developments in in ants and toddlers.Finally, we believe, these fndings provide a solid base or planning specifc observational or experi-mental studies aimed at refning, extending, vali-dating and contrasting results on any particularearly vocal behavior reported in this study.

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