The Development of Language Constancy: Attention to Native Versus

Nonnative Accents

Christine KitamuraUniversity of Western Sydney and University of Western

Sydney

Robin PannetonVirginia Tech

Catherine T. BestUniversity of Western Sydney and ??????1

The time frame for infants’ acquisition of language constancy was probed, using the phonetic variation in ararely heard accent (South African English) or a frequently heard accent (American English). A total of 156Australian infants were tested. Six-month-olds looked longer to Australian English than less commonly heardSouth African accent, but at 9 months, showed similar looking times. With the more frequently heard Ameri-can accent, 3-month-olds looked longer to Australian and American English, whereas 6-month-olds lookedequally. Together these results imply that in the first year, differential attention to native versus nonnativeaccents decreases as infants develop a sense of language constancy for the common native language. How-ever, experience with the nonnative accent can expedite this process.

Adults have little difficulty understanding mostpeople who speak in another accent of their lan-guage. Being language novices, infants and youngtoddlers must first discover that accented nativespeech is not a foreign language—yet virtuallynothing is known about how young infants handlethe pronunciation variants of regional accents. Atsome point in development, other regional accentsmust become acceptable as variants of that lan-guage. All speech contains phonetic variability dueto a range of talker characteristics, for example,gender, speech rate, emotional state, and speechstyle. However, unfamiliar accents present a specialperceptual challenge given that such speech con-tains both talker variability as well as variationmanifested in systematic differences in pronuncia-tion patterns. Although infants learn quite early inlife to accommodate the talker variability in theirown accent (Jusczyk, Pisoni, & Mullenix, 1992; Kuhl& Miller, 1982), little is known about how they

meet the challenge of identifying native languagestructure when it is spoken in an unfamiliar accent.

In the first year of life, infants cultivate a detailedknowledge of the sound patterning of their nativelanguage. Such knowledge requires that infantsmaintain or improve discrimination of native lan-guage phonemes, and at the same time show theability to ignore the differences in most nonnativecontrasts (Best, McRoberts, & Sithole, 1988; Werker& Lalonde, 1988; Werker & Tees, 1984). However,this is only one side of the story of attunement tothe native language, which also requires thatinfants perceive variation within the native lan-guage, including both talker-related variation andnative versus nonnative accents, as belonging to thesame language, despite pronunciation differences.As Best and colleagues have argued, word learningtoddlers need to grasp the complementary princi-ples of phonological distinctiveness and phonologicalconstancy (Best, Tyler, Gooding, Orlando, & Quann,2009). They must come to understand the function-ally crucial difference that occurs when a phonemicchange, for example, between two contrasting vow-els, signals two distinctive words, for example,“bears” and “beers”; versus ignoring the differences

This research was supported by funding from AustralianResearch Council Discovery Grant DP0772441 and a Universityof Western Sydney International Research Initiatives Scheme(80314). We thank Denis Burnham for encouraging the collabora-tion, and the mothers and babies and research assistants whohelped with the studies.

Correspondence concerning this article should be addressed toChristine Kitamura, Marcs Institute, University of Western Syd-ney, NSW, Australia. Electronic mail may be sent to c.kitamura@uws.edu.au2 .

© 2012 The Authors

Child Development © 2012 Society for Research in Child Development, Inc.

All rights reserved. 0009-3920/2012/xxxx-xxxx

DOI: 10.1111/cdev.12068

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Child Development, xxxx 2012, Volume 00, Number 0, Pages 1–15

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in pronunciation when a nonphonemic change inpronunciation still signals the same word, for exam-ple, “bears,” pronounced by Australian, BEHZ [bɛ:z], American, BEHRZ [bɛ z], or South African,BAIZ [be:z] talkers.

Toddlers’ grasp of the phonological constancy ofwords was assessed by Best et al. (2009) in twotests of listening preferences for high-frequency tod-dler versus low-frequency adult words. One testused the toddlers’ native accent, whereas the othertest used nonnative Jamaican English, an accentthat differs extensively from American English(AmE) (Patrick, 1999; Wassink, 2006); and that hadnot previously been experienced by the children.While 15- and 19-month-olds preferred toddlerwords over adult words in the native accent, onlythe 19-month-olds also preferred toddler words inthe nonnative Jamaican accent—an indication theyrecognize the words’ phonological constancydespite the unfamiliar accent (Best et al., 2009). Theauthors argue that earlier perceptual attunement tophonetic variability in native speech (e.g., Best,1994) underpins the ability of 19-month-olds toabstract a word’s constant phonological form acrossaccent variation, despite the distinctly different andunfamiliar pronunciations found in Jamaican Eng-lish.

The Best et al. results indicate a qualitative shiftin perception that cannot be entirely explained bymere exposure to linguistic input, such as has beenposited in statistical learning accounts (Best et al.,2009). That 19-month-olds recognize a word’s con-stant form despite unfamiliar accent differencessuggests the foundations of phonological constancyrest on perceptual attunement in the latter part ofthe first year. This attunement includes not only theability to ignore nonnative phonemic differencesbut also the ability to ignore unfamiliar pronuncia-tion differences in other regional accents. Recogni-tion that an unfamiliar accent has propertiesconsistent with common native language wouldindicate that young children have the capacity toabstract language common properties. In this view,abstraction may initially depend on episodic or sta-tistical learning involving memory of talker-idiosyn-cratic phonetic detail; however, it then goes wellbeyond these accumulated traces of surface details.That is, abstraction involves the discovery of higherlevel structure among lower level elements whosepatterns cannot predict such structure, particularlyif those patterns have not been previously experi-enced.

Two preliminary reports have assessed infants’adaptation to other accents (Diehl, Panneton,

Kitamura, & Burnham, 2006; Phan & Houston,2006). The first study tested regional accent prefer-ences of 6- and 8-month-old American infantsusing spontaneously produced sentences fromAmerican and Australian mothers. At 6 months ofage, American infants showed differential attentionto Australian- versus AmE, but at 8 months, theyshowed less consistent preferences (Diehl et al.,2006). The second study reported a decline in theability to distinguish regional accents using avisual habituation procedure (Phan & Houston,2006). It tested discrimination by infants at 7, 11,14, and 24 months using repetitions of a singleword “pine” where the differences in vowel pro-nunciation were typical of North Midland, PIE-N[p n] versus Southern AmE, PAHN [pa:n]. Notably,only the youngest group of 7-month-olds reliablydiscriminated the difference in vowel pronuncia-tions; older infants did not. Of importance is that,notwithstanding the different approaches (prefer-ence and habituation methods), both of these preli-minary findings revealed a similar pattern ofdevelopmental decline by 8+ months in responseto pronunciation differences between accents of thecommon native language.

The above results challenge current theories oflanguage acquisition that rest on infants’ exposureto the distributional properties of speech soundsheard in their home environment (i.e., statisticallearning). In statistical learning accounts, infants’exposure to the distributional properties of linguis-tic input guides their acquisition of the structuralproperties of the native language, such that by 8–9 months, infants are sensitive to native languagephonotactics (Jusczyk, Luce, & Charles-Luce, 1994)and transitional probabilities (Saffran, Aslin, &Newport, 1996). Infants are also sensitive to the dis-tributional regularities of native vowel input.Around 6 months, native vowel prototypes act as“perceptual magnets” for less prototypical vowelexemplars (Kuhl, 1991; Kuhl, Williams, Lacerda,Stevens, & Lindblom, 1992), but by 12 months,infants come to recognize that native languagevowel categories have perceptually flexible bound-aries and that “poorly formed” nonprototype pho-netic exemplars that lie at its outer edge still belongto the category (Polka & Werker, 1994). Indeed,infants show extraordinary sensitivity to the sto-chastic properties of speech input, such that 2 minof auditory-only exposure to a unimodal or bimo-dal distribution of phonetic units predicts discrimi-nation performance consistent with the exposeddistribution (Maye, Werker, & Gerken, 2002); asdoes exposure to a bimodal distribution enhance

2 Kitamura, Panneton, and Best

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infants’ ability to discriminate difficult nonnativecontrasts (Maye, Weiss, & Aslin, 2008).

Infants’ sensitivity to the distributional propertiesof language input provides a viable account of howinfants acquire the building blocks of native speech,but cannot account for children’s adaptations tounfamiliar regional accents. Certainly, infants canperceptually adapt to types of speech variabilitythey have experienced from an early age. Two-month-olds infants perceive vowels as equivalentacross variations in pitch (Kuhl & Miller, 1982);gender (Kuhl, 1983) and talkers (Jusczyk et al.,1992). In more demanding word segmentationtasks, 10-month-olds have the capacity to generalizeacross linguistic forms when the type of variationdiffers between familiarization and test conditionsalong dimensions of variation the infants have hadexperience with, for example, from a male to femalevoice (Houston & Jusczyk, 2000) or from happy toneutral vocal affect (Singh, Morgan, & White, 2004).Accumulated experience with such types of vari-ability is, thus, a reasonable explanation of why 10-,but not 7-month-old infants can generalize acrossspeakers and emotions (Houston & Jusczyk, 2000;Singh et al., 2004). As for accent variation, at 12–13 months infants successfully generalize acrossaccents that differ minimally (American vs. Cana-dian English) or maximally (American vs. Spanish-accented English) in word segmentation tasks,whereas 9-month-olds do not do so (Schmale, Cris-tia, Seidl, & Johnson, 2010; Schmale & Seidl, 2009).However, it remains unclear whether exposure toSpanish English or Canadian was a factor in thesestudies, given America’s large population ofHispanics, and closeness to Canada.

Infants’ ability to accommodate perceptually dif-ferent regional accents can provide unique insightsinto a language learning mechanism that eventuallycopes with abstracting across linguistic variationthat falls outside of the infant’s experience. More-over, by probing the constancy principle (asopposed to the distinctiveness principle), cross-accentstudies get to the core of an important debate onthe contributions of statistical learning versusabstraction processes in early language develop-ment. Statistical learning models posit that infants’linguistic knowledge derives from exposure to thedistribution of phonetic properties in speech inputin their native environment (Jusczyk, 1997; Saffranet al., 1996). Thus, if infants are exposed to Austra-lian English (AusE) only, then their vowel catego-ries should be restricted to the acoustic phoneticproperties of vowels in that accent, and not includephonetic variants from unfamiliar regional accents.

Behaviorally, this should result in infants payingmore attention to the properties of native speechwith their own familiar accent (high exposure) thannative speech with an unfamiliar accent (no expo-sure; see Nazzi, Jusczyk, & Johnson, 2000). In con-trast, an abstractionist account predicts that olderinfants’ linguistic knowledge is more than the accu-mulated traces of specific perceptual experience,and this enables infants to abstract the unifyingproperties of the common language (e.g., English)underlying the wide range of both familiar andunfamiliar accent variants. If infants are to achievelanguage constancy, they should be able to identifyspeech with a nonnative accent as consistent withtheir native language, even if the accent is unfamil-iar to them (analogous to Best et al., 2009; see alsoMetsala & Walley, 1998). Behaviorally, this shouldresult in infants paying equal attention to the prop-erties of native speech with either their own famil-iar accent or less familiar accent. We expect thatthis lack of differential attention should be evidentaround 9 months of age, consistent with priorresearch showing the emergence of perceptual reor-ganization in nonnative speech perception (e.g.,Werker & Tees, 1984), which indicates a burgeoningcapacity to ignore linguistic information in nonna-tive phonemes that is irrelevant to the native lan-guage (e.g., Conboy, Sommerville, & Kuhl, 2008).

We used a serial preference procedure to testAustralian infants’ attention to a standard set ofinfant-directed sentences spoken in familiar (i.e.,AusE), semifamiliar (i.e., AmE) and unfamiliar (i.e.,South African English [SAE]) English accents. Thefirst set of studies compared AusE and SAE accents.SAE is unfamiliar to most Australians, as it is rarelyencountered in the media or on the street, espe-cially in the areas of Sydney where our participantsare being raised. Our second set of studies com-pared AusE and AmE accents. AmE is a morefamiliar accent to Australians (even infants), giventhe AmE accent pervades all types of media (e.g.,movies, music, television, and radio). In the averageAustralian home, there is unavoidable and rathersubstantial exposure to the AmE accent through thepopularity of American programming on the living-room television set. Currently, of the programsbroadcast on free to air television in Australia, morethan half are American (Screen Australia, 2011,p. 46). Parents often watch television holding theirinfant or have it on in the background even whenthey are not watching it. To document Australianmothers’ television viewing habits, we surveyed 50mothers from our database. There were three mainfindings. Firstly, 64% of mothers reported having

The Development of Language Constancy 3

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the television turned on even when the family isnot watching it; secondly, 88% reported watchingtelevision while holding, feeding or playing withtheir infant when she was under 6 months of age;and thirdly, mothers’ favorite programs wereequally divided between Australian (47%) andAmerican programs (47%). British programs madeup only 6% of the total favorite programs. Giventhat Maye and others have shown that 2 min ofpurely auditory exposure to phonetic distributionsenhances or even changes perception at test (Mayeet al., 2002, 2008; Teinonen, Aslin, Alku, & Csibra,2008), the ambient background presence of AmE inthe majority of Australian homes is thus quite likelyto make it passively familiar to Australian infants.

Method

Regional accents can differ in terms of their vowels,consonants, and prosody, but the consensus fromanalyses of English accents is that the differencesmostly occur at the vowel level (Wells, 1982). How-ever, there are regional accents containing othertypes of variation. For example, when comparedwith AusE, the Welsh English accent differs mainlyin its prosodic realization (Wells, 1982); South EastLondon English is typified by consonantal differ-ences (Wells, 1982); and Jamaican Mesolect Englishdiffers from AusE at the vowel, consonant, and pro-sodic levels (Patrick, 1999; Wassink, 2006). Differ-ences between AusE, AmE, and SAE occur mainlyat the vowel level, which overshadow any smallvariations that might be found at the levels of con-sonants and prosody (Cox & Palthorpe, 2001; Lass,2007). Nonetheless, because infants find prosodyattractive, we controlled for any small prosodicdifferences among these three accents using infant-directed speech and matching our stimulus sen-tences across the accents, for mean fundamental fre-quency (pitch), pitch range, duration, and vocalaffect.

In terms of vowel differences, AmE and AusEdiffer in the distribution of vowels in formant (F1,F2) space (Agung, Purdy, & Kitamura, 2005; Labov,Ash, & Boberg, 2006; Lass, 2007; Wells, 1982). Forexample, the corner vowels/i/and/u/are morefronted in AusE than AmE, with the differencealong the F2 axis for/u/(AusE ~ 1750 Hz;AmE ~ 500 Hz) being much greater than for/i/(AusE ~ 2400 Hz; AmE ~ 2000 Hz; see Agunget al., 2005). There are also differences betweenAusE and SAE in the pronunciation of vowels. Forexample, to Australian listeners SAE six sounds like

sucks, and today like to die, and car like caw. AusEand AmE, however, can be further differentiatedbecause AmE is rhotic, but AusE and SAE are not.Rhotic speakers pronounce/r/in all positions, forexample, in words such as butter, nurse, and startwhereas nonrhotic speakers pronounce/r/in theword-initial position but generally not in word- orsyllable-final position, unless/r/is followed by avowel sound. For example, nonrhotic speakers pro-nounce/r/in red, and most pronounce it when/r/isfollowed by a vowel such as in horrid and watery,but not in hard, car or water. Thus, nonrhotic AusEand SAE can be classified as more phonetically sim-ilar than AusE and AmE because AmE has theadded feature of rhoticization (Lass, 2007).

Vowel space of AusE, SAE, and AmE. The utter-ances used in this study were as follows: “We camein our car, didn’t we?,” “Where’s your toy?,” “Let’slook for a game,” “Look at the orange bears,” and“Today is going to be so nice.” Vowel space wascalculated for our target materials in each of thethree accents using measures of the first and secondformant frequencies in the focus words of the sen-tences, that is, WE ? LOOK ? TOY ? NICE ?

CAR ? [CAME, GAME, TODAY] ? BEARS (?WE). The word WE was the final WE in the sen-tence, “We came in our car, didn’t we?” and wasreasonably stressed (unlike the initial WE), andused to ensure that the corner vowel/i/was plot-ted. Figure 1 provides a clear picture of the similar-ities and differences in the shape, size, and positionof the vowel space among the three accents for ourstimuli. Specifically, we can see, firstly, that AusEtruncates the entire vowel space along F2 (front-backtongue position) relative to AmE and SAE. Thismeans that the back vowels are more fronted inAusE than in AmE and SAE, and also that the frontvowels are less fronted (more centralized, orbacked). The front vowels are articulated fartherback in AmE, and less so in SAE. Secondly, AmEtruncates the front portion of vowel space along F1(jaw, vowel height) relative to AusE and SAE. WEand BEARS are lowered and [CAME, GAME,TODAY] is raised, and both BEARS and [CAME,GAME, TODAY] are fronted, which are thereforenearly identical in both F1 (height) and F2 (front-ness) in AmE. In both AusE and SAE, by contrast,BEARS and CAME are less fronted (lower F2), andBEARS is raised (lower F1) while CAME is lowered(higher F1)—there is a clear height differencebetween these two vowels in AusE and SAE.Thirdly, SAE expands the high back portion of vowelspace along F2 (front-back), relative to AusE andAmE. LOOK is backed in SAE relative to AusE,

4 Kitamura, Panneton, and Best

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and TOY is backed relative to both AusE and AmE.SAE also truncates the low back portion of vowelspace along F1 (height), relative to AusE andAmE. NICE and CAR are raised in SAE relative toAusE, and CAR is both raised and fronted relativeto AmE. Overall, SAE appears to raise the vowelspace by comparison to AusE and especially bycomparison to AmE.

Accent recordings. To create the accent record-ings, multiple utterance exemplars were producedby four Australian, four South African, and fourAmerican females in an infant-directed speech reg-ister. The Australian females were from the Sydneyregion of Australian, and spoke with a general Aus-tralian accent (Cox & Palthorpe, 2001). The SouthAfrican females originated from the Cape Townregion of South Africa, had been resident in Sydneyfor less than 5 years, and spoke respectable SAE(Lass, 2007). The American females were all nativeto the midregion of the Eastern U.S. (i.e., Pennsyl-vania, Maryland, Delaware, and Virginia) and allspoke with a midland American accent (Labov et al.,2006). For each regional accent, the recordings con-sisted of three different strings of the five utteranceslisted above, and included the four speakers in eachstring. The three strings were counterbalancedacross infant participants so that one-third of theinfants heard string order 1, 2, 3; one-third heardstring order 2, 3, 1; and one-third heard string order3, 1, 2. Utterances in each string were concatenatedand looped with a 500 ms interstimulus interval,and presented at 60–65 dB SPL (A).

Accent matching procedure. The acoustic andaffective characteristics that have been found to be

attentionally salient for young infants werematched across the sets of accent recordings: meanfundamental frequency (F0), range F0, duration andpositive affect (Fernald & Kuhl, 1987; Kitamura &Burnham, 1998; Panneton, Kitamura, Mattock, &Burnham, 2006; Singh, Morgan, & Best, 2002).Equating these features in the infant-directed regis-ter controlled not only for age-related responses toone regional accent set over the other set based onprosodic variation but also any idiosyncratic pro-sodic differences that might exist among the regio-nal accents. The acoustic dimensions of mean F0, F0range, and the duration were measured using Praat(Boersma & Weenink, 2005), and the level of posi-tive affect rated by 10 AusE adults on a scale of 1(none) to 10 (extreme) using utterances that werelow-pass filtered at 400 Hz to remove lexical con-tent. Means and standard deviations for each thethree strings of five utterances are shown inTable 1. T-tests showed there were no statisticaldifferences between AusE and SAE for mean F0(p > .4), F0 range (p > .3), duration (p > .4), or posi-tive affect (p > .7); nor for the differences betweenAusE and AmE for mean F0 (p > .6), F0 range(p > .9) or duration (p > .4), or positive affect(p > .4).

Study 1: Preferences for Australian VersusSAE at 6 months

In Study 1, we examined 6-month-old Australianinfants’ sensitivity to an unfamiliar regional accent,SAE. Previously examined American infants alsohad little or no exposure to the nonnative accent,British English (Nazzi et al., 2000) or AusE (Diehlet al., 2006). We expect Australian 6-month-oldswill follow the trend of American infants aroundthis age with an unfamiliar regional accent (Diehlet al., 2006; Nazzi et al., 2000) and show differentialattention to these regional accents, that is, prefertheir native AusE accent.

Participants. The sample consisted of 24 infants(12 females) aged 6 months (M = 26.2 weeks,range = 24.4–27.4 weeks). Infants were selected onlyif both parents reported coming from monolingualAusE-speaking families. In addition, parentalreports indicated that all infants were born at fullterm, were healthy at the time of testing, had nohistory of chronic or acute ear infections, and nohearing impairment. An additional four infantswere excluded due to fussiness or crying.

Accent recordings. The accent recordings usedwere the AusE and SAE strings.

A u s ES A EA m E

Figure 1.3 Vowel space for the primary stressed vowels in targetutterances for the regional accents used in this report: AustralianEnglish, South African English, and American English.

LOW

RESOLUTIO

NFIG

The Development of Language Constancy 5

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Procedure. An infant fixation-controlled serialpreference procedure was used to test differentialattention to the native versus the nonnative accent.In the preference procedure, infants sat on theirparent’s lap in a sound-attenuated test room facinga video monitor placed slightly to the right of theinfant’s midline. A camera placed directly in frontof the infant was connected to a video monitor inthe adjacent room. The experimenter in the controlroom judged the infant’s head and eye movementsonline from the image on a second video monitorin the control room. At the beginning of each trial,the infant’s attention was drawn to the monitorwith a set of silent flashing multicolored circles.Once the infant fixated the monitor for 2 s, a bulls-eye appeared on the screen and testing began. Oneach trial, presentation of utterances of the speci-fied regional accent for that trial was controlled bythe infants’ fixation on the colored bulls-eye, andcontinued until the infant looked away for morethan 2 consecutive seconds or until a total of 40 sof looking had elapsed. Then, the infant’s monitorflashed the multicolored circles until the infantlooked back, at which time the bulls-eye reap-peared and the next trial began. There were six tri-als of each accent, with each accent presented onalternating trials for a total of 12 trials. The orderof presentation in trials was counterbalanced acrossparticipants, so that half the infants heard thenative accent first, and the other half heard thenonnative accent first. The experimenter was blindto the order of trials. To diminish parental influ-ence, the same utterances but mixed across regionalaccents and with all the silences removed wereplayed to parents using a portable CD player andstudio headphones.

Results and Discussion

The dependent variable was mean fixation dura-tion averaged across the six test trials for eachaccent type. Mean fixation durations to AusE andSAE by 6-month-old Australian infants are shownin the left-side panel of Figure 2. The data were ana-lyzed in a (2) 9 2 analysis of variance (ANOVA)with accent (AusE–SAE) within participants, andorder of accent presentation (AusE first–SAE first)between participants. The results revealed a signifi-cant main effect for accent: Australian 6-month-oldslooked longer to hear AusE (M = 19.6, SE = 1.6)than SAE (M = 16.5, SE = 1.5), F(1, 22) = 8.2,p = .009, gp

2= .28. The main effect for order and

the Accent 9 Order interaction were both nonsignif-icant (both ps > .5). The results show that 6-month-olds listen longer to hear AusE than SAE, that is,they are capable of distinguishing the systematicdifferences in SAE versus AusE, and prefer thenative accent. This finding accords with other accentperception studies using infants around this age andunfamiliar regional accents (Diehl et al., 2006; Nazziet al., 2000; Phan & Houston, 2006).

Study 2: Preferences for Australian VersusSAE at 9 months

Study 2 assessed 9-month-olds’ preferences forAusE versus the unfamiliar accent, SAE to examinethe developmental trajectory whereby infantsachieve language constancy for an unfamiliar non-native accent. We tested 9-month-olds becauseother studies have shown a decline in differentialattention to accents at 8+ months (Diehl et al., 2006;

Table 1

Average Acoustic Featuresa and Affective Ratingsb for South African English (SAE), Australian English (AusE), and American English (AmE)

Utterance Strings

Utterance strings

Mean F0 (Hz) Range (Hz) Duration (s) Positive affect

SAE AusE AmE SAE AusE AmE SAE AusE AmE SAE AusE AmE

String 1 mean 278.3 275.0 279.8 352.7 312.4 310.0 2.3 2.1 1.9 7.4 7.3 6.8

SD 61.2 35.2 41.4 71.0 60.0 60.1 0.5 0.8 0.5 0.5 0.8 0.6

String 2 mean 263.5 222.4 251.0 271.2 236.2 232.4 2.4 2.1 1.9 6.5 6.1 7.1

SD 30.8 13.2 29.4 91.1 58.2 61.8 0.4 0.6 0.5 0.7 0.9 1.1

String 3 mean 286.3 266.8 276.2 316.7 296.4 285.2 2.3 2.0 1.9 7.1 7.6 6.3

SD 48.8 41.8 40.3 59.1 64.6 60.9 0.6 0.8 0.4 0.9 1.0 0.6

Grand mean 276.0 254.7 269.0 313.5 281.7 275.9 2.3 2.1 1.9 7.0 7.0 6.7

SD 47.0 30.0 37.0 73.7 60.9 60.9 0.5 0.7 0.5 0.7 0.9 0.8

aMean F0 (Hz), F0 range (Hz), duration (s). bPositive affect: 1 = low to 10 = high.

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Phan & Houston, 2006), and this is an age whichoverlaps with the emergence of perceptual reorgani-zation in nonnative language phonemic perception.Study 1 showed a fine-tuned sensitivity in 6-month-olds to the differences between their own accentand a similar nonnative regional accent. Nonethe-less, at some later developmental point infantsshould come to recognize that the two accentsreflect the same language, and therefore show adecline in attention to the differences among regio-nal accents of their native language.

Participants. The sample consisted of 24 infants(12 females) aged 9 months (M = 38.6 weeks,range = 36.7–40.3 weeks). The selection criteria wereidentical to Study 1. An additional 3 infants wereexcluded due to fussiness or crying.

Accent recordings. The accent recordings wereidentical to those used in Experiment 1, that is, theAusE and SAE strings.

Procedure. The same procedure was used asdescribed in Study 1.

Results and Discussion

The dependent variable was mean fixation dura-tion averaged across the six test trials for each ofthe AusE and SAE accents. The left-side panel ofFigure 2 shows mean fixation durations to AusEand SAE by 9-month-old Australian infants. Thedata were analyzed in a (2) 9 2, Accent (AusE–SAE) 9 Presentation order (AusE first–SAE first)ANOVA. The ANOVA revealed no significant maineffect for accent (p > .2) or order (p > .3), Noraccent 9 Order interaction (p > .3). The overall fixa-tion times of infants aged 9 months was similar forAusE (M = 13.1, SE = 1.2) and SAE (M = 11.7,

SE = 1.4). Notably, 9-month-old Australian infantsdo not show a preference for AusE or SAE. Takentogether, the results of Studies 1 and 2 indicate thatbetween the ages of 6 and 9 months, infants accom-modate to pronunciation differences between theirown and a previously unheard accent, and do notprefer AusE over SAE as 6 month-olds do. The crit-ical point is that infants come to recognize the pho-netic commonalties of the English language acrossregional accents, even without exposure to thenovel SAE pronunciations.

In this study, the preference procedure testedinfants’ attentional biases. However, it is unclearwhether the 9-month-olds expressed no selectiveattention to these two accents in spite of their abil-ity to discriminate their differences, or that theirlack of preference reflects a more active normaliza-tion across accents such that infants at this age donot discriminate AusE and SAE as distinct. The lat-ter interpretation is supported by the results ofPhan and Houston (2006) who did not find discrim-ination of words differing in regional accents in asample of similarly aged infants. The recognition oflanguage constancy might indicate a decline in theability to discriminate between the accents (e.g.,Phan & Houston, 2006), or on the other hand,infants may recognize language constancy despiteretaining the ability to distinguish two accents. Forexample, adults show fine-tuned sensitivity toregional accent differences even though they easilyrecognize other accents as belonging to their nativelanguage (Campbell-Kibler, 2010) and can recognizewords and phrases across accents. To better under-stand the lack of preference in Study 2, we used thesame sentence strings to test a new group of 9-month-old infants using a discrimination proce-dure.

Study 3: Discrimination of Australian VersusSAE at 9 months

The current study tested 9-month-old Australianinfants’ ability to discriminate AusE and SAE usingan infant-controlled visual habituation procedure.This allowed us to test the possibility that Austra-lian 9-month-olds find AusE and SAE equally inter-esting, but still discriminate between them. It alsoprovides a deeper understanding of the perceptualbasis for the development of language constancy,and how it relates to adults’ ability to simulta-neously recognize that other regional accentsbelong to the same language and yet that twoaccents are different.

* *051 01 52 02 5

M eanFi xati on( secs)6 M o n t h s 9 M o n t h s 6 M o n t h s 3 M o n t h sU n f a m i l i a r S A E A c c e n t F a m i l i a r A m E A c c e n t

A u s E S A E A m EFigure 2. Developmental changes in Australian infants’ attentionto the differences between native Australian English (AusE)versus two nonnative accents of English: unfamiliar South Afri-can English and familiar AmE accent. Asterisks indicate signifi-cant looking differences between AusE and the opposing accent.Error bars = 1 SE of the mean.

The Development of Language Constancy 7

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Participants. The sample consisted of 24 infants(12 females) aged 9 months (M = 38.6 weeks,range = 35.7–42.3 weeks). The selection criteria wereidentical to Study 1. An additional 12 infants wereexcluded due to fussiness (3) or failure to habituate(9; see Procedure).

Accent recordings. The accent recordings wereidentical to those used in Experiment 1, that is, theAusE and SAE strings.

Procedure. All procedural details except for thesequencing of the trials were identical to the serialpreference procedure described in Study 1.Sequencing of trials was as follows: One accent waspresented on repeated trials until there was anaverage 50% decrement in fixation durations overtwo consecutive trials compared to the average ofthe first two trials. Best et al. used a two-trial crite-rion with a visual-fixation habituation procedure,and both studies found significant dishabituationfor native speech contrasts as well as for nonnativeclick consonant contrasts (Best, McRoberts, Lafleur,& Silverstadt, 1995; Best et al., 1988). In addition,we included two no-change control trials (of thehabituation stimulus) which were presented imme-diately after the habituation criterion was met, toensure infants had indeed habituated, and notshown regression to the mean (Cohen, 2004). Thisallowed us to remove infants (from the analysis)who showed spontaneous recovery in fixation dura-tion during no-change control trials (see Bertenthal,Haith, & Campos, 1983). Spontaneous recovery wasdefined as an average 100% increase in fixationdurations in the two no-change control trials com-pared to average of the final two habituation trials.The use of no-change control trials directly follow-ing habituation trials more carefully controls failureto habituate than having the control trials at theend of or interspersed with test trials. The no-change control trials were followed by two test tri-als, which comprised the other accent. Half of theinfants were habituated to AusE and heard AmE inthe test trials, and the other half of the infants werehabituated with AmE and heard AusE in the testtrials. Infants are said to discriminate the two setsof stimuli if they show a significant recoveryresponse (longer fixation durations) in the test trialscompared to the no-change trials.

Results and Discussion

The dependent variable was mean fixation dura-tion, which was averaged across the final twohabituation trials, across the two no-change controltrials, and across the two test trials. Data were

entered in a (3; trial type) 9 2 (accent order) ANO-VA, with trial type (habituation vs. control vs. test)within participants, and accent order (AusE–SAE)between participants. For trial types, two plannedcontrasts tested (a) recovery in control trials com-pared to habituation trials to ensure no recoveryoccurred between habituation and control trials,and (b) recovery of fixation in test trials comparedto control trials. There were no main effects for thecontrast testing habituation versus control (p > .26),or control versus test (p > .21), or for presentationorder (p > .44) nor the effects of Trial type 9 Orderinteractions (ps > .45). On average infants lookedfor statistically similar times in the last two habitua-tion trials (M = 4.9, SE = 0.5), the two control trials(M = 5.2, SE = 0.5), and the two test trials (M = 6.0,SE = 0.7). Of the 24 infants, 18 infants looked lessin the test trials than no-change control trials.

Taken together, the first three studies reveal aloss of sensitivity to unfamiliar English accent pro-nunciations between 6 and 9 months of age, usingeither visual habituation or preference procedures.Phan and Houston (2006) also report a failure todiscriminate North Midland versus Southern Ameri-can accents at 11, 14, and 24 months, but showedsuccessful discrimination at 7 months, using visualhabituation. These findings are contrary to what wemight expect of adults who are quite sensitive toaccent differences, yet recognize that accents belongto the same language. Adults have learned thataccents allow them to identify an individual’s socialorigin yet at the same time treat other accents asfunctionally equivalent to their own. A first step forinfants, therefore, might be to treat accents equiva-lently, to eventually understand what the talker ofanother accent is saying. Indeed, by 19 monthsinfants recognize familiar words spoken in Jamai-can English, despite their very different pronuncia-tions and having no experience of Jamaican English(Best et al., 2009).

Important to an abstractionist view is that thereis a loss of sensitivity to nonnative accent pronunci-ations even without exposure to the novel pronun-ciation, SAE. However, this reasoning implies thatthe developmental trajectory should differ for afamiliar nonnative accent. But, infants have neverbeen tested with a familiar nonnative accent. Otherstudies used accents unfamiliar to American infants:Australian (Diehl et al., 2006) and British English(Nazzi et al., 2000), and found that 5- to 7-month-olds detect differences between their own and theunfamiliar regional accents (see also Butler, Floccia,Goslin, & Panneton, 2010). In the next study, there-fore, we tested Australian infants with the regional

8 Kitamura, Panneton, and Best

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accent AmE, which is familiar to Australian infantsdue exposure via media. If Australian infants treatAusE and AmE as equivalent at an earlier age thanthe unfamiliar SAE accent, this would suggest thatstatistical learning plays a role through exposure tothe AmE accent.

Study 4: Preferences for Australian VersusAmE at 6 months

In Study 4, the serial preference procedure (same asthat used in Study 1 and 2) was used to test6-month-olds’ attention to AusE versus the familiarrhotic AmE accent. There were two possible out-comes. The first possibility was that Australian6-month-olds would behave like American infantsaround this age (Diehl et al., 2006; Nazzi et al.,2000; Phan & Houston, 2006) and the 6-month-oldsin Study 1, and show differential attention to AusEand AmE. The second possibility was that Austra-lian 6-month-olds would be equally responsive toAusE and AmE accents, unlike American infants.That outcome would suggest that exposure to pop-ular American media influences accent perception,such that Australian 6-month-olds come to includeAmE within the common structure of the Englishlanguage sooner than American infants include theunfamiliar AusE accent, or AusE infants include theunfamiliar SAE accent.

Participants. The sample consisted of 24 infants(11 females) aged 6 months (M = 26.1 weeks,range = 24.3–27.7 weeks). The selection criteria wereidentical to Study 1. An additional three infantswere excluded due to failure to habituate.

Accent recordings. The accent recordings usedwere the AusE and AmE strings.

Procedure. The same procedure was used asdescribed in Study 1.

Results and Discussion

The dependent variable was mean fixation dura-tion averaged across the six test trials for AusEversus the six trials for AmE. The right panelof Figure 2 shows mean fixation durations of6-month-olds to AusE and AmE. The data wereanalyzed in a (2) 9 2 ANOVA with accent (AusE–AmE) within participants, and order of presentation(AusE first–AmE first) between participants. Theresults revealed no significant main effects foraccent or order. The 6-month-old Australian infantsshowed similar fixation times to AusE (M = 17.0,SE = 1.1) and AmE (M = 16.0, SE = 1.3). There was

only a marginally Significant accent 9 Order inter-action, F(1, 22) = 3.1, p = .09, weakly suggesting thepossibility that Australian infants looked longer tohear AusE (M = 16.7, SE = 1.8) than AmE(M = 13.4, SE = 1.7) when AusE was heard in thefirst trial, but that when AmE was presented firstinfants looked slightly longer to AmE (M = 18.4,SE = 1.8) than AusE (M = 17.3, SE = 1.3). Tworesults are worthy of note, firstly, that overall Aus-tralian 6-month-olds failed to look longer to AusEor AmE, but secondly, there was a marginal ten-dency for infants to look longer to the first accentthey heard.

To explore the Marginal accent 9 Order interac-tion further for insights about the infants’ failure toshow an overall accent preference, we conducted ablock analysis to determine how infants behavedin the first block of three trials versus the secondblock of three trials. The (2; accent) 9 2 (order) 9(2; block) ANOVA revealed a significant main effectfor block, F(1, 22) = 15.5, p = .001, gp

2= .41, and

a Significant accent 9 Order 9 Block interaction,F(1, 22) = 8.8, p = .007, gp

2= .29. As expected,

infants looked longer in the first than the secondhalf of the trials, but more critically, as shown inFigure 3, the three-way interaction indicates thatthe order effect was stronger in the first than thesecond block of the trials. In the first block of thetrials, with AusE heard first, infants listened longerto AusE (M = 20.2) than AmE (M = 14.0), withAmE heard first, infants listened longer to AmE(M = 24.0) than AusE (M = 19.6). That is, they pre-fer the accent they heard in the first test trial.

Block 1 Block 1Block 2 Block 20

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AusE First AmE First

AusE AmE

Figure 3. Mean fixation durations (s) to Australian English(AusE) and American English (AmE) by 6-month-old Australianinfants as a function of whether infants heard AusE first or AmEfirst and the first and second block of three trials. Errorbars = 1 SE of the mean. There were no differences betweenAusE or AmE in either block; there was an order effect indicat-ing a reliable preference for the first accent heard for bothaccents in the first but not the second block of test trials.

The Development of Language Constancy 9

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However, in the second half of the trials the differ-ences in attention were much smaller (for AmE 1st:AusE M = 14.9; AmE M = 12.8; for AusE 1st: AusEM = 13.11; AmE M = 12.3). Simple effects wereexamined in a (2; accent) 9 2 (order) ANOVA foreach the first and second block. The results showno difference in looking time for AusE or AmE ineither block, but they do show a Significantaccent 9 Order interaction for the first block, F(1,22) = 8.6 p = .006, alone (second block: p = .35).Thus, the order effect was evident in the first halfof the trials but not the second half—infants in thefirst half of the trials looked longer to the regionalaccent heard first, and by the second half perceivedAusE and AmE as equivalent. Because the blockanalysis suggests infants accommodate to accentdifferences fairly easily, post hoc block analyseswere performed for the AusE versus SAE data inStudies 1 and 2. Neither ANOVA with AusE versusSAE for 6- or 9-month-olds showed even marginalevidence of a Dialect 9 Order 9 Block interaction.

In Study 1, Australian 6-month-olds preferredAusE over unfamiliar SAE, but in this study theyshowed no overall preference when the familiarAmE accent was used. The block analysis revealedthat 6-month-old Australian infants preferred theaccent heard first (AmE or AusE) in the first block,but not the second block of trials. Familiarity withthe AmE accent would appear to be the precursorfor this recognition of equivalence between thesetwo accents by the second half of the preferencetrials in this study. Even a small amount of every-day exposure during the first 6 months of theinfant’s life seems to have influenced accent percep-tion to the extent they treat the first accent theyhear as familiar, and may explain why 6-month-oldAustralian infants easily come to recognize thecommon features of AusE and AmE over the courseof a short study. Of course, there may be other rea-sons for this result. Nonetheless, to show evidenceof the development of language constancy, wewould need to find evidence that younger Austra-lian infants with less language experience show anAusE accent preference between AusE and AmE.This was examined in Study 5.

Study 5: Preferences for Australian VersusAmE at 3 months

The aim of Study 5 was to test a younger group ofAustralian infants with AusE and AmE on thepremise that 6-month-olds’ ability to ignore pro-nunciations differences was due to exposure to

AmE via popular media (Screen Australia, 2011, p.46). If exposure to AmE was responsible, thenyounger 3-month-olds with less exposure to AmEaccent should show a native accent preference.

Participants. The sample consisted of 24 infants(12 females) aged 3 months (M = 15.1 weeks,range = 13.2–17.7 weeks) from monolingual AusE-speaking families. The selection criteria were identi-cal to Study 1. An additional 3 infants wereexcluded due to fussiness or crying.

Accent recordings. The accent recordings wereidentical to those used in Experiment 4, that is, theAusE and AmE strings.

Procedure. The same procedure was used asdescribed in Study 1.

Results and Discussion

The dependent variable was mean fixation dura-tion averaged across the six test trials for each accenttype. The right-side panel of Figure 2 shows meanfixation durations to AusE and AmE by 3-month-oldAustralian infants. A (2; accents) 9 2 (presentationorder) ANOVA revealed a significant main effect foraccent, F(1, 22) = 8.4, p < .008, gp

2= .28, a marginal

main effect for order, F(1, 22) = 3.45, p < .08,gp

2 = .14, but no Accent 9 Order interaction(p > .27). That is, regardless of whether 3-month-oldAustralian infants heard AusE or AmE first, they lis-tened significantly longer to AusE (M = 18.8,SE = 1.5) than AmE (M = 15.6, SE = 1.3). The mar-ginal effect for presentation order suggests that Aus-tralian infants showed somewhat longer overallfixation durations when they heard AmE first(M = 19.4, SE = 1.8) than when they heard AusEfirst (M = 14.9, SE = 1.9). However, the main findingis that, unlike 6-month-olds, 3-month-old Australianinfants prefer listening to AusE over AmE. The pres-ent findings provide support for the view that olderinfants are more likely to ignore the differencesbetween their own versus another native languageaccent than younger 3-month-olds who still treat theAmE accent as different to their own Australianaccent.

Study 6: Discrimination of AusE Versus AmE &AusE Versus SAE at 6 months

In Study 6, we directly test the effects of accentfamiliarity on 6-month-old’s discrimination behaviorusing a visual habituation method, with the goal ofreplicating the results of Study 1 using SAE andStudy 4 using AmE, which used the preferential

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attention method. In Study 1, Australian 6-month-olds preferred their own accent over SAE, and inStudy 4, Australian 6-month-olds failed to showpreferential attention to AusE or AmE. Thus, Study6 compared Australian 6-month-olds’ ability to dis-criminate AusE versus familiar AmE or AusE versusunfamiliar SAE.

Participants. For the group tested with AusE andAmE, the sample consisted of 18 infants (10 females)aged 6 months (M = 26.4 weeks, range = 24.3–27.7 weeks). The selection criteria were identical toStudy 1. An additional five infants were notincluded due to failure to habituate (4) or technicalfaults (1) during testing. For the group tested withSAE, the sample consisted of 18 infants (6 females)aged 6 months (M = 25.7 weeks, range = 23.3–27.4 weeks). Using identical selection criteria anadditional three infants were not included due tofailure to habituate.

Accent recordings. The AusE, AmE, and SAEaccent recordings were identical to the strings usedin previous experiments.

Procedure. The same infant-controlled habitua-tion procedure was used to test accent discrimina-tion as in Study 3.

Results and Discussion

The dependent variable was mean fixation dura-tion averaged across the final two habituation trials,across the two no-change control trials, and acrossthe two test trials. Mean fixation durations for thetwo infant groups are shown in Figure 4. Data wereentered in a 2 (group) 9 (2) order 9 (3; trial type)ANOVA, with group (familiar AmE, unfamiliarSAE), order (AusE vs. SAE, or AusE vs. AmE)between participants, and (trial type (habituation,control, test) within participants. For trial type, twoplanned contrasts tested (a) recovery in control tri-als compared to habituation trials, and (b) recoveryof fixation in test trials compared to control trials.There were no main effects for the contrast testinghabituation versus control (p > .5), or for presenta-tion order (p > .4) nor was the 3-way Group 9

Order 9 Trial type interaction significant (ps > .3).However, the main effect testing the differencebetween control versus test trials was significant,F(1, 32) = 7.4, p = .01, gp

2 = .19, as was the inter-action for Group 9 Control versus test, F(1, 32) =6.5, p = .016, gp

2 = .17. As shown in Figure 4, the6-month-old Australian group who heard AusEversus SAE showed evidence of discrimination, asthey looked longer in the test trials (M = 9.2,SE = 1.0) than control trials (M = 5.2, SE = 0.6).

However, the group who heard AusE versus AmElooked similarly in the control trials (M = 8.0,SE = 0.8) and the test trials (M = 8.1, SE = 1.2). Ofthe 18 infants tested with AmE versus AusE, onlyfour infants had longer looking times in the testthan the no-change control trials whereas for theinfants tested with SAE versus AusE, 16 of the 18infants showed evidence that they could discrimi-nate the two accents.

Testing 6-month-olds with a visual habituationprocedure confirms our findings with the prefer-ence method. Infants at this age remain sensitive tothe differences between AusE and SAE, but show alack of sensitivity to AusE–AmE differences. Therewas no evidence of an Accent order 9 Trial typeinteraction, as it made no difference whether infantswere habituated with their own AusE accent andtested with a nonnative accent or vice versa. Habit-uation generally taps into infants’ sensitivity toacoustic and phonetic differences, thus it appearsthat 6-month-old infants’ familiarity with a nonna-tive accent determines how they respond to accentdifferences. If it is a familiar accent (AmE) they canaccommodate to the accent differences but if theaccent is unfamiliar (SAE), at 6 months of age,infants remain sensitive to the accent difference.

General Discussion

This set of studies investigated the effects of ageand accent familiarity on Australian infants’ atten-

Figure 4. 4Mean fixation (seconds) in habituation, control and testtrials for Australian infants hearing familiar American Englishversus Australian English (AusE) and unfamiliar South AfricanEnglish versus AusE. Error bars = 1 SE of the mean.

LOW

RESOLUTIO

NFIG

The Development of Language Constancy 11

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tion to native versus nonnative English regionalaccents. Previously, it has been shown that infantsaround 6 months of age display differential atten-tion to their own and another unfamiliar regionalaccent (Diehl et al., 2006; Nazzi et al., 2000; Phan &Houston, 2006). In this study, when AusE is com-pared with the rarely heard, unfamiliar SAE accent,our findings correspond to others’ findings (Diehlet al., 2006; Nazzi et al., 2000; Phan & Houston,2006): Australian 6-month-olds show an accent pref-erence. In contrast, older 9-month-olds respondequivalently to AusE and SAE whether tested witha preference or habituation method. Thus, with ararely experienced accent, our study and othersfound that older Australian infants do not exhibitdifferential attention regardless of testing procedure(serial preference; see Diehl et al., 2006 or habitua-tion; see Phan & Houston, 2006). This suggests thatby 9 months of age, infants are able to ignore thesystematic differences in accent pronunciationsdespite their lack of exposure to another regionalaccent, and abstract the base language structureshared by the accents.

Nine-month-olds’ ability to recognize their nativelanguage, despite its spoken form containing unfa-miliar accent variants, is compatible with the impor-tant ability of older toddlers to recognize wordsacross disparate accents, or phonological constancy(Best et al., 2009). The recognition of constancyappears to emerge simultaneously with infants’ abil-ity to ignore nonnative consonant and vowel con-trasts and as perceptual sensitivity to nativecontrasts increases (distinctiveness). Our findingssuggest that infants’ ability to recognize that differ-ent regional accents share common language charac-teristics is an antecedent to the ability to recognizewords despite highly variant pronunciations.

Interestingly, different aspects of our findingssupport both distributional and abstractionist learn-ing accounts. When infants are familiar with a non-native accent, AmE in this study, the developmentaltrajectory is shifted earlier: 6-month-old Australianinfants do not discriminate AusE and AmE. In somesense, this finding is consistent with a statisticallearning view, corroborating other findings that lan-guage exposure influences speech perception, evenin short experimental sessions (Maye et al., 2002).Infants appear to be tracking recurring phonetic pat-terns in the speech environment so that over time,the flexibility of their phonemic boundaries isstretched, in this case, to include phonetic variantsof AmE heard on the families’ television set. How-ever, given the SAE accent is never or rarely heard,distributional learning cannot explain older infants’

ability to assimilate this accent into their Englishprocessing. That older infants ignore accent varia-tion they have never experienced in SAE suggestsan abstraction mechanism is at work, with infantsshowing an emerging ability to abstract propertiesof language that exist beyond the perceptual tracesof their experience.

Exploiting the systematic phonetic variation thatexists in pronunciation differences between nativeand nonnative accents has the potential to uncoveran important principle essential for early languageacquisition—the recognition of language constancy.Moreover, language constancy appears to parallelother linguistically relevant developments thatemerge during the final quarter of the first year.Around the first birthday infants successfully recog-nize words in the face of accent variation in wordsegmentation tasks, but 9-month-olds do not(Schmale & Seidl, 2009; Schmale et al., 2010). Simi-larly, around 10 months, infants have the capacity toabstract linguistic forms in the face of variation dueto the talker’s gender (Houston & Jusczyk, 2000) orvocal affect (Singh et al., 2004). More important, it isat this age that infants begin to ignore many nonna-tive phonemic contrasts (Best et al., 1988; Werker &Lalonde, 1988; Werker & Tees, 1984) as they attuneto native language phonemic categories.

Coinciding with the leap forward in speech per-ception around 9–12 months are improved infantcognitive abilities. Lalonde and Werker (1995)tested the coincidental timing of changes to cogni-tion and speech perception at 10 months, usingnonnative consonant discrimination and two cogni-tive tasks. Infants who showed evidence of percep-tual reorganization for the speech task were alsosuccessful on the cognitive tasks, whereas infantswho discriminated the nonnative speech contrastfailed the cognitive tasks (Lalonde & Werker, 1995).Similarly, 10-month-olds’ capacity to ignore differ-ences in a nonnative contrast predicts both moreadvanced cognitive control (Conboy et al., 2008);and larger receptive vocabularies at later ages(Kuhl, Conboy, Padden, Nelson, & Pruitt, 2005;Tsao, Lui, & Kuhl, 2004). These studies indicate thatperceptual reorganization is a part of a larger pic-ture that involves the emergence of other higherorder cognitive competencies, including aspects oflanguage development. Moreover, central to ourfocus on the emergence of language constancy, thefindings indicate that the ability to ignore irrelevantlinguistic information is a crucial cornerstone in thefoundation for language acquisition.

For the accents used in this set of studies, the dif-ferences reside primarily at the level of vowels, not

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at the consonant or suprasegmental level (see Cox& Palthorpe, 2001; Labov et al., 2006; Lass, 2007;Wells, 1982), and these differences in pronunciationare mostly subphonemic in nature (see Figure 1). Ifsuprasegmental variation was implicated, then itcould be expected that infants would get better withage at discriminating their own and another accentbecause infants’ ability to make fine-grain prosodicdiscriminations improves rather than worsens inspeech rhythm studies (Hayashi, Tamekawa, &Kiritani, 2001; Jusczyk, Cutler, & Redanz, 1993). Butinstead, we (and two others) have found that pref-erential attention to the native dialect declines, indi-cating an improvement in the ability to ignore thesystematic segmental variation in other dialects. Thisdecline is analogous to the developmental declinereported for discrimination of nonnative segmentalcontrasts, where infants improve in their ability toignore nonnative phonemic distinctions. While ourresults do not show that infants treat individualphonemes with perceptual equivalence, or indeedthat it is vowels and not consonants that are impli-cated, they do show that in continuous speechinfants treat the subphonemic but systematic pro-nunciation differences in other English accents asfunctionally equivalent to their own native accentby the third quarter of the first year for an unfamil-iar accent, and by midway through the year for afamiliar accent.

We might ask why infants group accents into thesame language category, when we know that adultseasily distinguish one regional accent from another.For adults, regional accent functions as an impor-tant social marker enabling the listener to identifythe speaker’s geographic and ethnic origin, andsocial status (Wells, 1982). However, it is alsoimportant that adults comprehend what a speakerof another accent is saying, and therefore, adultsalso need to have an understanding that those otheraccent types belong to the same underlying nativelanguage. Thus, the recognition of language con-stancy in first year of life is an important precursorfor learning the phonological constancy of wordspronounced very differently from what the childhas previously experienced (Best et al., 2009). How-ever, at some later point in development, the childshould be able to recognize an accent as different totheir own for social purposes that they have cometo understand through broader experience. Phanand Houston (2006) found that even at 24 monthsinfants did not discriminate their own and anotherregional accent. By 5 years, however, children showpreferences for a person talking in their nativeaccent as opposed to one talking with a foreign

accent (Kinzler, Dupoux, & Spelke, 2007). Thus, theability to use accent variation as a marker of socio-linguistic differences among speakers appears toemerge sometime between 2 and 5 years. Probingchildren’s emerging abilities to recognize the dualfeatures of accent variation (language constancy vs.social origin differences) would enhance insight intothe development and organization of early speechperception abilities, within their proper social con-text. It is possible that the recovery of native accentrecognition by 5 years signals more sophisticatedspeech perception abilities that cleverly coordinatesensitivity to both linguistic regularities and socio-linguistic differences.

Infants’ perception of nonnative accent pronunci-ations of the native language provides a compellingtest of language constancy. While we know nativelanguage experience improves infants’ ability to dis-tinguish native and nonnative languages (Hayashiet al., 2001), our results suggest that language expe-rience also improves infants’ ability to ignore lin-guistically irrelevant accent variants within themother tongue by the end of the first year. Under-pinning this skill is the ability to perceive constancyin the structure of utterances despite the unfamiliarpronunciations found in other regional accents. Thetime course for this burgeoning sense of languageconstancy appears to parallel the course for attune-ment to native language phonemes, which alsoinvolves the ability to ignore differences in nonna-tive contrasts that are irrelevant to distinguishingamong words in the native language (Best & McRo-berts, 2003; Polka & Werker, 1994; Werker & Tees,1984). Moreover, within the native language (Eng-lish) evidence of higher order phonological con-stancy for deviant pronunciations of words inJamaican Mesolect English is demonstrated inAmE-learning infants at 19 but not 15 months ofage (Best et al., 2009). We argue that languageconstancy is a prerequisite for achieving that levelof phonological constancy for words, a central prin-ciple for early word learning. The experimental useof regional accents to probe the listener’s attune-ment to the native language is a promising meansof examining how young children come to abstractmeaning from a speech signal, and conversely toignore differences that are not linguistically mean-ingful in the language they are learning.

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O n c e y o u h a v e A c r o b a t R e a d e r o p e n o n y o u r c o m p u t e r , c l i c k o n t h e C o m m e n t t a b a t t h e r i g h t o f t h e t o o l b a r :

S t r i k e s a l i n e t h r o u g h t e x t a n d o p e n s u p a t e x tb o x w h e r e r e p l a c e m e n t t e x t c a n b e e n t e r e d .‚ H i g h l i g h t a w o r d o r s e n t e n c e .‚ C l i c k o n t h e R e p l a c e ( I n s ) i c o n i n t h e A n n o t a t i o n ss e c t i o n .‚ T y p e t h e r e p l a c e m e n t t e x t i n t o t h e b l u e b o x t h a ta p p e a r s .

T h i s w i l l o p e n u p a p a n e l d o w n t h e r i g h t s i d e o f t h e d o c u m e n t . T h e m a j o r i t y o ft o o l s y o u w i l l u s e f o r a n n o t a t i n g y o u r p r o o f w i l l b e i n t h e A n n o t a t i o n s s e c t i o n ,p i c t u r e d o p p o s i t e . W e ’ v e p i c k e d o u t s o m e o f t h e s e t o o l s b e l o w :S t r i k e s a r e d l i n e t h r o u g h t e x t t h a t i s t o b ed e l e t e d .

‚ H i g h l i g h t a w o r d o r s e n t e n c e .‚ C l i c k o n t h e S t r i k e t h r o u g h ( D e l ) i c o n i n t h eA n n o t a t i o n s s e c t i o n .

H i g h l i g h t s t e x t i n y e l l o w a n d o p e n s u p a t e x tb o x w h e r e c o m m e n t s c a n b e e n t e r e d .‚ H i g h l i g h t t h e r e l e v a n t s e c t i o n o f t e x t .‚ C l i c k o n t h e A d d n o t e t o t e x t i c o n i n t h eA n n o t a t i o n s s e c t i o n .‚ T y p e i n s t r u c t i o n o n w h a t s h o u l d b e c h a n g e dr e g a r d i n g t h e t e x t i n t o t h e y e l l o w b o x t h a ta p p e a r s .

M a r k s a p o i n t i n t h e p r o o f w h e r e a c o m m e n tn e e d s t o b e h i g h l i g h t e d .‚ C l i c k o n t h e A d d s t i c k y n o t e i c o n i n t h eA n n o t a t i o n s s e c t i o n .‚ C l i c k a t t h e p o i n t i n t h e p r o o f w h e r e t h e c o m m e n ts h o u l d b e i n s e r t e d .‚ T y p e t h e c o m m e n t i n t o t h e y e l l o w b o x t h a ta p p e a r s .

I n s e r t s a n i c o n l i n k i n g t o t h e a t t a c h e d f i l e i n t h ea p p r o p r i a t e p a c e i n t h e t e x t .‚ C l i c k o n t h e A t t a c h F i l e i c o n i n t h e A n n o t a t i o n ss e c t i o n .‚ C l i c k o n t h e p r o o f t o w h e r e y o u ’ d l i k e t h e a t t a c h e df i l e t o b e l i n k e d .‚ S e l e c t t h e f i l e t o b e a t t a c h e d f r o m y o u r c o m p u t e ro r n e t w o r k .‚ S e l e c t t h e c o l o u r a n d t y p e o f i c o n t h a t w i l l a p p e a ri n t h e p r o o f . C l i c k O K .

I n s e r t s a s e l e c t e d s t a m p o n t o a n a p p r o p r i a t ep l a c e i n t h e p r o o f .‚ C l i c k o n t h e A d d s t a m p i c o n i n t h e A n n o t a t i o n ss e c t i o n .‚ S e l e c t t h e s t a m p y o u w a n t t o u s e . ( T h e A p p r o v e ds t a m p i s u s u a l l y a v a i l a b l e d i r e c t l y i n t h e m e n u t h a ta p p e a r s ) .‚ C l i c k o n t h e p r o o f w h e r e y o u ’ d l i k e t h e s t a m p t oa p p e a r . ( W h e r e a p r o o f i s t o b e a p p r o v e d a s i t i s ,t h i s w o u l d n o r m a l l y b e o n t h e f i r s t p a g e ) .

A l l o w s s h a p e s , l i n e s a n d f r e e f o r m a n n o t a t i o n s t o b e d r a w n o n p r o o f s a n d f o rc o m m e n t t o b e m a d e o n t h e s e m a r k s . .‚ C l i c k o n o n e o f t h e s h a p e s i n t h e D r a w i n gM a r k u p s s e c t i o n .‚ C l i c k o n t h e p r o o f a t t h e r e l e v a n t p o i n t a n dd r a w t h e s e l e c t e d s h a p e w i t h t h e c u r s o r .‚

T o a d d a c o m m e n t t o t h e d r a w n s h a p e ,m o v e t h e c u r s o r o v e r t h e s h a p e u n t i l a na r r o w h e a d a p p e a r s .‚

D o u b l e c l i c k o n t h e s h a p e a n d t y p e a n yt e x t i n t h e r e d b o x t h a t a p p e a r s .