Holding on to childhood language memory

Phonetic perceptual reorganization across the first year of life: Looking back

This paper provides a selective overview of some of the research that has followed from the publication of Werker and Tees (1984a) "Cross-language speech perception: Evidence for Perceptual Reorganization During the First Year of Life." Specifically, I briefly present the original finding, our interpretation of its meaning, and some key replications and extensions. I then review some of the work that has followed, including work with different kinds of populations, different kinds of speech sound contrasts, as well as attunement (perceptual reorganization) to additional properties of language beyond phonetic contrasts. Included is the body of work that queries whether perceptual attunement is a critical period phenomenon. Potential learning mechanisms for how experience functions to guide phonetic perceptual development are also presented, as is work on the relation between speech perception and word learning.

Phonetic and Lexical Encoding of Tone in Cantonese Heritage Speakers

Heritage speakers contend with at least two languages: the less dominant first language (L1), that is, the heritage language, and the more dominant second language (L2). In some cases, their L1 and L2 bear striking phonological differences. In the current study, we investigate Toronto-born Cantonese heritage speakers and their maintenance of Cantonese lexical tone, a linguistic feature that is absent from English, the more dominant L2. Across two experiments, Cantonese heritage speakers were tested on their phonetic/phonological and lexical encoding of tone in Cantonese. Experiment 1 was an AX discrimination task with varying inter-stimulus intervals (ISIs), which revealed that heritage speakers discriminated tone pairs with disparate pitch contours better than those with shared pitch contours. Experiment 2 was a medium-term repetition priming experiment, designed to extend the findings of Experiment 1 by examining tone representations at the lexical level. We observed a positive correlation between English dominance and priming in tone minimal pairs that shared contours. Thus, while increased English dominance does not affect heritage speakers' phonological-level representations, tasks that require lexical access suggest that heritage Cantonese speakers may not robustly and fully distinctively encode Cantonese tone in lexical memory.

Perceptual Categorization of Hñäñho-Specific Vowel Contrasts by Hñäñho Heritage Speakers in Mexico

For a large proportion of Mexican Indigenous speakers, it is common for the use of their native languages to shift across generations towards Spanish, the majority language in Mexico. This specific population can be defined as heritage speakers (HS) of their indigenous language, since many of them are Spanish-dominant bilinguals with a strong connection to their minority native language and culture, both of which they might only maintain in their family home where they were raised. The present study investigates the perceptual sensitivity of HS of Santiago Mexquititlán Otomi (Hñäñho) towards sounds of their native language to examine if these HS can accurately categorize Hñäñho vowels or whether their categorization is influenced by their dominant Spanish vowel system. Twelve Hñäñho HS (HHS) and twelve Mexican Spanish monolinguals (MSM) listened to the Hñäñho-specific vowel contrasts /a – ɔ/ and /ɔ – o/ and categorized them among the vowels of their respective mother tongue. Our results indicate that HHS correctly categorize vowels /a/ and /o/, which exist in both Hñäñho and Spanish, but do not accurately categorize the Hñäñho-specific vowel /ɔ/. Moreover, HHS and MSM showed similar patterns in terms of the proportion of /ɔ/ categorized as either /a/ and /o/. These results have implications for the maintenance of language-specific vowel contrasts and the vowel system of a minority language, such as Hñäñho, in the context of language shift towards Spanish in Mexico.

Crosslinguistic Influence in the Discrimination of Korean Stop Contrast by Heritage Speakers and Second Language Learners

The present study examines the extent of crosslinguistic influence from English as a dominant language in the perception of the Korean lenis–aspirated contrast among Korean heritage speakers in the United States (N = 20) and English-speaking learners of Korean as a second language (N = 20), as compared to native speakers of Korean immersed in the first language environment (N = 20), by using an AX discrimination task. In addition, we sought to determine whether significant dependencies could be observed between participants’ linguistic background and experiences and their perceptual accuracy in the discrimination task. Results of a mixed-effects logistic regression model demonstrated that heritage speakers outperformed second language learners with 85% vs. 63% accurate discrimination, while no significant difference was detected between heritage speakers and first language-immersed native speakers (85% vs. 88% correct). Furthermore, higher verbal fluency was significantly predictive of greater perceptual accuracy for the heritage speakers. The results are compatible with the interpretation that the influence of English on the discrimination of the Korean laryngeal contrast was stronger for second language learners of Korean than for heritage speakers, while heritage speakers were not apparently affected by dominance in English in their discrimination of Korean lenis and aspirated stops.

Preliminary Results on the Development of the Perception of Spanish /e/ and /ei/ by Heritage Learners vs. L2 Learners of Spanish in the Classroom

This exploratory study gives a first glance at the development of the perception of the Spanish /e/-/ei/ contrast by heritage learners in comparison to that of L2 learners in the classroom. To this end, two types of semester-long, explicit phonetic instruction training are compared: High Phonetic Variability Training (HPVT) with exposure to multiple sources of speech, and regular standalone phonetics courses with low variability of speech input (LPVT). Data from two identical pre-test and post-test ABX perceptual discrimination tasks were obtained from 27 students, as well as 7 control speakers whose primary language is Spanish. Results show that heritage learners perceive the contrast better than L2 learners, and that HPVT significantly improves the perception of the /e/-/ei/ contrast. Although heritage learners perform close to a native ceiling and do not significantly differ from native controls, the improvement from pre-test to post-test is larger in heritage learners enrolled in HPVT than LPVT training. These results suggest that, although the discrimination accuracy of Spanish /e/ and /ei/ is already high for heritage learners at the pre-test stage, High Phonetic Variability Training can be beneficial in the perceptual development of their heritage language, even matching their accuracy to that of native speakers.

Modeling Heritage Language Phonetics and Phonology: Toward an Integrated Multilingual Sound System

Although heritage language phonology is often argued to be fairly stable, heritage language speakers often sound noticeably different from both monolinguals and second-language learners. In order to model these types of asymmetries, I propose a theoretical framework—an integrated multilingual sound system—based on modular representations of an integrated set of phonological contrasts. An examination of general findings in laryngeal (voicing, aspiration, etc.) phonetics and phonology for heritage languages shows that procedures for pronouncing phonemes are variable and plastic, even if abstract may representations remain stable. Furthermore, an integrated multilingual sound system predicts that use of one language may require a subset of the available representations, which illuminates the mechanisms that underlie phonological transfer, attrition, and acquisition.

Heritage Tagalog Phonology and a Variationist Framework of Language Contact

Heritage language variation and change provides an opportunity to examine the interplay of contact-induced and language-internal effects while extending the variationist framework beyond monolingual speakers and majority languages. Using data from the Heritage Language Variation and Change in Toronto Project, we illustrate this with a case study of Tagalog (r), which varies between tap, trill, and approximant variants. Nearly 3000 tokens of (r)-containing words were extracted from a corpus of spontaneous speech of 23 heritage speakers in Toronto and 9 homeland speakers in Manila. Intergenerational and intergroup analyses were conducted using mixed-effects modeling. Results showed greater use of the approximant among second-generation (GEN2) heritage speakers and those that self-report using English more. In addition, the distributional patterns remain robust and the approximant appears in more contexts. We argue that these patterns reflect an interplay between internal and external processes of change. We situate these findings within a framework for distinguishing sources of variation in heritage languages: internal change, identity marking and transfer from the dominant language.

Bilingual phonological development across generations: Segmental accuracy and error patterns in second- and third-generation British Bengali children

INTRODUCTION

While developmental norms for speech sound development have been widely reported for monolingual children, and increasingly for bilingual children, little is known about speech sound development across different generations of children growing up in heritage language settings. The purpose of the present study was to gain a better understanding of inter-generational differences in the phonological development of British Bengali children.

METHODS

Typically-developing second-generation and third-generation Bengali heritage children living in Wales (n=19), aged between 4 and 5 years, participated in a picture-naming task in Sylheti and English. The single-word speech samples were transcribed phonetically and analyzed in terms of consonant and vowel accuracy measures, and error patterns. Subsequently, logistic mixed-effects regression models were fitted to identify the factors that predict accurate speech patterns in the children's productions.

RESULTS

The results revealed high levels of accuracy in consonant and vowel production by both sets of children, particularly in English. On Sylheti consonants, second-generation children significantly outperformed third-generation children, however only on language-specific sounds. In contrast, generation was not a significant predictor for accuracy on English consonants, but all children performed better on shared sounds than on English-specific categories, and on stops than affricates. The third-generation children exhibited a greater number of error types in Sylheti than the second-generation children, and more common replacement of Sylheti dental stops with alveolars.

CONCLUSION

The results suggest that third-generation children have less developed pronunciation patterns in the heritage language, but not the majority language, than their age-matched second-generation peers, however only on language-specific sounds. These findings indicate that differentiating between the phonological norms of monolingual and bilingual children may not be clinically sufficiently sensitive, at least in the minority language, and that more fine-grained language use variables, such as the generation to which a bilingual child belongs, need to be considered.

Phonological Production in Young Speakers of Cantonese as a Heritage Language

This study investigates the phonological production of 50 heritage speakers of Cantonese aged 5-11 in the USA. They were compared to 12 majority language speaker peers in Hong Kong via ratings from first language adult speakers. Overall, the heritage speakers were rated as less native-like and less comprehensible than the children in Hong Kong, although they received higher scores from raters speaking the same variety of Cantonese (i.e., Guangzhou Cantonese, vs. Hong Kong Cantonese). None of the tested language background factors, including age of testing, had a predictive effect on the heritage speakers' scores. The results illustrate the divergence and heterogeneity of heritage phonology compared to homeland varieties.

Intelligibility of first-language (L1) and second-language (L2) speech by switched-dominance Spanish-English bilinguals

Recordings of Spanish and English sentences by switched-dominance bilingual (SDB) Spanish (i.e., L2-dominant Spanish-English bilinguals) and by L1-dominant Spanish and English controls were presented to L1-dominant Spanish and English listeners, respectively. At -4 dB signal-to-noise ratio (SNR), Spanish and English productions by SDBs were equally intelligible with both reaching L1-dominant control levels. At -8 dB SNR, SDB English intelligibility matched that of L1-dominant English controls, yet SDB Spanish intelligibility was significantly lower than that of L1-dominant Spanish controls. These results emphasize that extended (but not early) exposure is both necessary and sufficient for robust speech learning.

Exposure to a second language in infancy alters speech production

We evaluated the impact of exposure to a second language on infants' emerging speech production skills. We compared speech produced by three groups of 12-month-old infants while they interacted with interlocutors who spoke to them in Spanish and English: monolingual English-learning infants who had previously received 5 hours of exposure to a second language (Spanish), English- and Spanish-learning simultaneous bilinguals, and monolingual English-learning infants without any exposure to Spanish. Our results showed that the monolingual English-learning infants with short-term exposure to Spanish and the bilingual infants, but not the monolingual English-learning infants without exposure to Spanish, flexibly matched the prosody of their babbling to that of a Spanish- or English-speaking interlocutor. Our findings demonstrate the nature and extent of benefits for language learning from early exposure to two languages. We discuss the implications of these findings for language organization in infants learning two languages.

English only? Monolinguals in linguistically diverse contexts have an edge in language learning

Accumulating evidence shows how language context shapes bilingual language use and its cognitive consequences. However, few studies have considered the impact of language context for monolinguals. Although monolinguals' language processing is assumed to be relatively stable and homogeneous, some research has shown novel learning through exposure alone. Monolinguals living in linguistically diverse contexts regularly overhear languages they do not understand, and may absorb information about those languages in ways that shape their language networks. The current study used behavioral and ERP measures to compare monolinguals living in a linguistically diverse environment and a unilingual environment in their ability to learn vowel harmony in Finnish. Monolinguals in both contexts demonstrated similar learning of studied words; however, their ERPs differed for generalization. Monolinguals in the diverse context revealed an anterior late positivity, whereas monolinguals in the unilingual context showed no effect. The results suggest that linguistic diversity promotes new language learning.

The Effects of Code-Switching and Lexical Stress on Vowel Quality and Duration of Heritage Speakers of Spanish

The quantity of research on Heritage Speakers (HS) of Spanish phonetics has increased over the last decade, including studies on the possible effect of code-switching on Spanish phonetics. Following this line of research, the present study investigates the role of code-switching and lexical stress on Spanish HS vowel production, specifically if the introduction of English reduces the vowel quality and duration of Spanish vowels after a code-switch. Eleven Spanish HSs participated in a controlled narration task in which they were asked to read aloud texts that code-switched between English and Spanish and one text that only contained Spanish. PRAAT was used to segment the vowels and the F1 and F2 values, along with duration, were extracted. The results show that both code-switching and lexical stress significantly affect Spanish HS vowels. Code-switching and vowels in unstressed position were more centralized than the vowels in the monolingual Spanish session and vowels in stressed position, respectively; unstressed vowels were also shorter in duration than stressed vowels. These results show that the introduction of English—a language in which vowel quality and duration change between unstressed and stressed syllables—via code-switching significantly affects Spanish HS vowels, subsequently providing evidence for transient interference.

How Does L1 and L2 Exposure Impact L1 Performance in Bilingual Children? Evidence from Polish-English Migrants to the United Kingdom

Most studies on bilingual language development focus on children's second language (L2). Here, we investigated first language (L1) development of Polish-English early migrant bilinguals in four domains: vocabulary, grammar, phonological processing, and discourse. We first compared Polish language skills between bilinguals and their Polish non-migrant monolingual peers, and then investigated the influence of the cumulative exposure to L1 and L2 on bilinguals' performance. We then examined whether high exposure to L1 could possibly minimize the gap between monolinguals and bilinguals. We analyzed data from 233 typically developing children (88 bilingual and 145 monolingual) aged 4;0 to 7;5 (years;months) on six language measures in Polish: receptive vocabulary, productive vocabulary, receptive grammar, productive grammar (sentence repetition), phonological processing (non-word repetition), and discourse abilities (narration). Information about language exposure was obtained via parental questionnaires. For each language task, we analyzed the data from the subsample of bilinguals who had completed all the tasks in question and from monolinguals matched one-on-one to the bilingual group on age, SES (measured by years of mother's education), gender, non-verbal IQ, and short-term memory. The bilingual children scored lower than monolinguals in all language domains, except discourse. The group differences were more pronounced on the productive tasks (vocabulary, grammar, and phonological processing) and moderate on the receptive tasks (vocabulary and grammar). L1 exposure correlated positively with the vocabulary size and phonological processing. Grammar scores were not related to the levels of L1 exposure, but were predicted by general cognitive abilities. L2 exposure negatively influenced productive grammar in L1, suggesting possible L2 transfer effects on L1 grammatical performance. Children's narrative skills benefitted from exposure to two languages: both L1 and L2 exposure influenced story structure scores in L1. Importantly, we did not find any evidence (in any of the tasks in which the gap was present) that the performance gap between monolinguals and bilinguals could be fully closed with high amounts of L1 input.

Early phonology revealed by international adoptees' birth language retention

Until at least 6 mo of age, infants show good discrimination for familiar phonetic contrasts (i.e., those heard in the environmental language) and contrasts that are unfamiliar. Adult-like discrimination (significantly worse for nonnative than for native contrasts) appears only later, by 9-10 mo. This has been interpreted as indicating that infants have no knowledge of phonology until vocabulary development begins, after 6 mo of age. Recently, however, word recognition has been observed before age 6 mo, apparently decoupling the vocabulary and phonology acquisition processes. Here we show that phonological acquisition is also in progress before 6 mo of age. The evidence comes from retention of birth-language knowledge in international adoptees. In the largest ever such study, we recruited 29 adult Dutch speakers who had been adopted from Korea when young and had no conscious knowledge of Korean language at all. Half were adopted at age 3-5 mo (before native-specific discrimination develops) and half at 17 mo or older (after word learning has begun). In a short intensive training program, we observe that adoptees (compared with 29 matched controls) more rapidly learn tripartite Korean consonant distinctions without counterparts in their later-acquired Dutch, suggesting that the adoptees retained phonological knowledge about the Korean distinction. The advantage is equivalent for the younger-adopted and the older-adopted groups, and both groups not only acquire the tripartite distinction for the trained consonants but also generalize it to untrained consonants. Although infants younger than 6 mo can still discriminate unfamiliar phonetic distinctions, this finding indicates that native-language phonological knowledge is nonetheless being acquired at that age.

Early development of abstract language knowledge: evidence from perception-production transfer of birth-language memory

Children adopted early in life into another linguistic community typically forget their birth language but retain, unaware, relevant linguistic knowledge that may facilitate (re)learning of birth-language patterns. Understanding the nature of this knowledge can shed light on how language is acquired. Here, international adoptees from Korea with Dutch as their current language, and matched Dutch-native controls, provided speech production data on a Korean consonantal distinction unlike any Dutch distinctions, at the outset and end of an intensive perceptual training. The productions, elicited in a repetition task, were identified and rated by Korean listeners. Adoptees' production scores improved significantly more across the training period than control participants' scores, and, for adoptees only, relative production success correlated significantly with the rate of learning in perception (which had, as predicted, also surpassed that of the controls). Of the adoptee group, half had been adopted at 17 months or older (when talking would have begun), while half had been prelinguistic (under six months). The former group, with production experience, showed no advantage over the group without. Thus the adoptees' retained knowledge of Korean transferred from perception to production and appears to be abstract in nature rather than dependent on the amount of experience.

Production and Perception of the /i/-/I/ Vowel Contrast: The Case of L2-Dominant Early Learners of English

The present study explored the production and perception of the /i/-/I/ vowel contrast in second language (L2)-dominant early learners of American English who no longer fluently speak their first language (L1, Spanish). The production task analyzed the extent to which the early learner group differed from controls (native English speakers and L1-Spanish late-onset learners of English) with regard to duration and spectral centroids. The perception experiment examined how these early learners classified resynthesized stimuli drawn from the /i/-/I/ contrast using distinct acoustic cues - spectral and temporal - in a 2-alternative forced choice identification task. The first experiment revealed that the early learners produced the contrast in a native-like manner in terms of the spectral envelope and duration use. The second experiment found that early learners differed from both control groups in how they categorized the /i/-/I/ continua based on spectrum and duration, and the extent to which they rely on these two cues. The effects of linguistic experience on L2 phonetic behavior are discussed.

The irreversibility of sensitive period effects in language development: evidence from second language acquisition in international adoptees

The question of a sensitive period in language acquisition has been subject to extensive research and debate for more than half a century. While it has been well established that the ability to learn new languages declines in early years, the extent to which this outcome depends on biological maturation in contrast to previously acquired knowledge remains disputed. In the present study, we addressed this question by examining phonetic discriminatory abilities in early second language (L2) speakers of Swedish, who had either maintained their first language (L1) (immigrants) or had lost it (international adoptees), using native speaker controls. Through this design, we sought to disentangle the effects of the maturational state of the learner on L2 development from the effects of L1 interference: if additional language development is indeed constrained by an interfering L1, then adoptees should outperform immigrant speakers. The results of an auditory lexical decision task, in which fine vowel distinctions in Swedish had been modified, showed, however, no difference between the L2 groups. Instead, both L2 groups scored significantly lower than the native speaker group. The three groups did not differ in their ability to discriminate non-modified words. These findings demonstrate that L1 loss is not a crucial condition for successfully acquiring an L2, which in turn is taken as support for a maturational constraints view on L2 acquisition. A video abstract of this article can be viewed at: https://youtu.be/1J9X50aePeU.

Can non-interactive language input benefit young second-language learners?

To fully acquire a language, especially its phonology, children need linguistic input from native speakers early on. When interaction with native speakers is not always possible - e.g. for children learning a second language that is not the societal language - audios are commonly used as an affordable substitute. But does such non-interactive input work? Two experiments evaluated the usefulness of audio storybooks in acquiring a more native-like second-language accent. Young children, first- and second-graders in Hong Kong whose native language was Cantonese Chinese, were given take-home listening assignments in a second language, either English or Putonghua Chinese. Accent ratings of the children's story reading revealed measurable benefits of non-interactive input from native speakers. The benefits were far more robust for Putonghua than English. Implications for second-language accent acquisition are discussed.

Critical periods in speech perception: new directions

A continuing debate in language acquisition research is whether there are critical periods (CPs) in development during which the system is most responsive to environmental input. Recent advances in neurobiology provide a mechanistic explanation of CPs, with the balance between excitatory and inhibitory processes establishing the onset and molecular brakes establishing the offset of windows of plasticity. In this article, we review the literature on human speech perception development within the context of this CP model, highlighting research that reveals the interplay of maturational and experiential influences at key junctures in development and presenting paradigmatic examples testing CP models in human subjects. We conclude with a discussion of how a mechanistic understanding of CP processes changes the nature of the debate: The question no longer is, "Are there CPs?" but rather what processes open them, keep them open, close them, and allow them to be reopened.

Raspberry, not a car: context predictability and a phonological advantage in early and late learners' processing of speech in noise

Second language learners perform worse than native speakers under adverse listening conditions, such as speech in noise (SPIN). No data are available on heritage language speakers’ (early naturalistic interrupted learners’) ability to perceive SPIN. The current study fills this gap and investigates the perception of Russian speech in multi-talker babble noise by the matched groups of high- and low-proficiency heritage speakers (HSs) and late second language learners of Russian who were native speakers of English. The study includes a control group of Russian native speakers. It manipulates the noise level (high and low), and context cloze probability (high and low). The results of the SPIN task are compared to the tasks testing the control of phonology, AXB discrimination and picture-word discrimination, and lexical knowledge, a word translation task, in the same participants. The increased phonological sensitivity of HSs interacted with their ability to rely on top–down processing in sentence integration, use contextual cues, and build expectancies in the high-noise/high-context condition in a bootstrapping fashion. HSs outperformed oral proficiency-matched late second language learners on SPIN task and two tests of phonological sensitivity. The outcomes of the SPIN experiment support both the early naturalistic advantage and the role of proficiency in HSs. HSs’ ability to take advantage of the high-predictability context in the high-noise condition was mitigated by their level of proficiency. Only high-proficiency HSs, but not any other non-native group, took advantage of the high-predictability context that became available with better phonological processing skills in high-noise. The study thus confirms high-proficiency (but not low-proficiency) HSs’ nativelike ability to combine bottom–up and top–down cues in processing SPIN.

Mapping the unconscious maintenance of a lost first language

Optimal periods during early development facilitate the formation of perceptual representations, laying the framework for future learning. A crucial question is whether such early representations are maintained in the brain over time without continued input. Using functional MRI, we show that internationally adopted (IA) children from China, exposed exclusively to French since adoption (mean age of adoption, 12.8 mo), maintained neural representations of their birth language despite functionally losing that language and having no conscious recollection of it. Their neural patterns during a Chinese lexical tone discrimination task matched those observed in Chinese/French bilinguals who have had continual exposure to Chinese since birth and differed from monolingual French speakers who had never been exposed to Chinese. They processed lexical tone as linguistically relevant, despite having no Chinese exposure for 12.6 y, on average, and no conscious recollection of that language. More specifically, IA participants recruited left superior temporal gyrus/planum temporale, matching the pattern observed in Chinese/French bilinguals. In contrast, French speakers who had never been exposed to Chinese did not recruit this region and instead activated right superior temporal gyrus. We show that neural representations are not overwritten and suggest a special status for language input obtained during the first year of development.

The effects of age on second language grammar and speech production

The current study examined the age of learning effect on second language (L2) acquisition. The research goals of the study were twofold: to test whether there is an independent age effect controlling for other potentially confounding variables, and to clarify the age effect across L2 grammar and speech production domains. The study included 118 Mandarin-speaking immigrants and 24 native English speakers. Grammar knowledge was assessed by a grammaticality judgment task, and speech production was measured by native English speaking raters' ratings of participants' foreign accents. Results from the study revealed that the age of learning effect was robust for both L2 domains even after controlling for the influences of other variables, such as length of residence and years of education in the United States. However, the age of learning variable had a stronger impact on speech production than on grammar. The current results support the framework of multiple critical/sensitive periods (Long in Int Rev Appl Linguist 43(4):287-317, 2005; Newport et al. in Language, brain and cognitive development: Essays in honor of Jacques Mehler. MIT Press, Cambridge, MA, 2001; Werker and Tees in Dev Psychobiol 46(3):233-251, 2005).

Perceptual narrowing: retrospect and prospect

Research is reviewed demonstrating perceptual narrowing across a variety of domains. Research is also reviewed showing that the temporal window of perceptual narrowing can be extended and, in some cases, perceptual narrowing can be reversed. Research is also reviewed highlighting the neurophysiological correlates of perceptual narrowing as well as some of the individual neurophysiological differences associated with perceptual narrowing. Various methodological issues associated with perceptual narrowing are also discussed. The broader purpose of this paper, however, is to argue that the term perceptual narrowing fails to capture the dynamic nature of this perceptual process. Finally, it is argued that just as other concepts associated with experience and development are refined and modified as new evidence emerges, likewise we need to evaluate and refine how we conceptualize perceptual narrowing.

Age-related sensitive periods influence visual language discrimination in adults

Adults as well as infants have the capacity to discriminate languages based on visual speech alone. Here, we investigated whether adults' ability to discriminate languages based on visual speech cues is influenced by the age of language acquisition. Adult participants who had all learned English (as a first or second language) but did not speak French were shown faces of bilingual (French/English) speakers silently reciting sentences in either language. Using only visual speech information, adults who had learned English from birth or as a second language before the age of 6 could discriminate between French and English significantly better than chance. However, adults who had learned English as a second language after age 6 failed to discriminate these two languages, suggesting that early childhood exposure is crucial for using relevant visual speech information to separate languages visually. These findings raise the possibility that lowered sensitivity to non-native visual speech cues may contribute to the difficulties encountered when learning a new language in adulthood.

Narrowing perceptual sensitivity to the native language in infancy: exogenous influences on developmental timing

The infancy literature situates the perceptual narrowing of speech sounds at around 10 months of age, but little is known about the mechanisms that influence individual differences in this developmental milestone. We hypothesized that such differences might in part be explained by characteristics of mother-child interaction. Infant sensitivity to syllables from their native tongue was compared longitudinally to sensitivity to non-native phonemes, at 6 months and again at 10 months. We replicated previous findings that at the group level, both 6- and 10- month-olds were able to discriminate contrasts in their native language, but only 6-month-olds succeeded in discriminating contrasts in the non-native language. However, when discrimination was assessed for separate groups on the basis of mother-child interaction-a 'high contingency group' and a 'moderate contingency' group-the vast majority of infants in both groups showed the expected developmental pattern by 10 months, but only infants in the 'high contingency' group showed early specialization for their native phonemes by failing to discriminate non-native contrasts at 6-months. The findings suggest that the quality of mother-child interaction is one of the exogenous factors influencing the timing of infant specialization for speech processing.

Transactional associations between supportive family climate and young children’s heritage language proficiency in immigrant families

Heritage language (HL) proficiency confers developmental benefits; however, the onset of HL loss is observed among many young children from immigrant families. In this longitudinal study, transactional associations between children’s HL proficiency and supportive family climate were examined in Chinese immigrant families with pre-school-aged children. Parental warmth, cultural maintenance values, and use of HL support were investigated as aspects of family climate. Measures included observable parent–child interactions and performance-based language proficiency assessments. While parental cultural maintenance values appeared influential, parental behavioral support of HL showed more robust prospective associations with children’s HL development. Concurrently, children’s earlier HL proficiency predicted subsequent parental behavior; parents whose children had limited HL proficiency decreased their use of HL support 1 later. Implications of the findings are discussed for immigrant parents with young children.

Production of phonetic and phonological contrast by heritage speakers of Mandarin

This study tested the hypothesis that heritage speakers of a minority language, due to their childhood experience with two languages, would outperform late learners in producing contrast: language-internal phonological contrast, as well as cross-linguistic phonetic contrast between similar, yet acoustically distinct, categories of different languages. To this end, production of Mandarin and English by heritage speakers of Mandarin was compared to that of native Mandarin speakers and native American English-speaking late learners of Mandarin in three experiments. In experiment 1, back vowels in Mandarin and English were produced distinctly by all groups, but the greatest separation between similar vowels was achieved by heritage speakers. In experiment 2, Mandarin aspirated and English voiceless plosives were produced distinctly by native Mandarin speakers and heritage speakers, who both put more distance between them than late learners. In experiment 3, the Mandarin retroflex and English palato-alveolar fricatives were distinguished by more heritage speakers and late learners than native Mandarin speakers. Thus, overall the hypothesis was supported: across experiments, heritage speakers were found to be the most successful at simultaneously maintaining language-internal and cross-linguistic contrasts, a result that may stem from a close approximation of phonetic norms that occurs during early exposure to both languages.

Evidence for a Sensitive Period for Acculturation

Though recent adult immigrants often seem less acculturated to their new society than people who immigrated as children, it is not clear whether this difference is driven by duration of exposure or exposure during a sensitive developmental period. In a study aimed at disambiguating these influences, community and student samples of Hong Kong immigrants to Vancouver, Canada, completed the Vancouver Index of Acculturation, a measure that assesses respondents’ identification with their mainstream and heritage cultures. A longer duration of exposure was found to be associated with greater identification with Canadian culture only at younger ages of immigration, but not at later ages of immigration. Conversely, identification with Chinese culture was unaffected by either age of immigration or length of exposure to Canadian culture. These findings provide evidence for a sensitive period for acculturation: People are better able to identify with a host culture the longer their exposure to it, but only if this exposure occurs when they are relatively young.

Early childhood language memory in the speech perception of international adoptees

It is as yet unclear whether the benefits of early linguistic experiences can be maintained without at least some minimal continued exposure to the language. This study compared 12 adults adopted from Korea to the US as young children (all but one prior to age one year) to 13 participants who had no prior exposure to Korean to examine whether relearning can aid in accessing early childhood language memory. All 25 participants were recruited and tested during the second week of first-semester college Korean language classes. They completed a language background questionnaire and interview, a childhood slang task and a Korean phoneme identification task. Results revealed an advantage for adoptee participants in identifying some Korean phonemes, suggesting that some components of early childhood language memory can remain intact despite many years of disuse, and that relearning a language can help in accessing such a memory.

Plasticity of illusory vowel perception in Brazilian-Japanese bilinguals

Previous research shows that monolingual Japanese and Brazilian Portuguese listeners perceive illusory vowels (/u/ and /i/, respectively) within illegal sequences of consonants. Here, several populations of Japanese-Brazilian bilinguals are tested, using an explicit vowel identification task (experiment 1), and an implicit categorization and sequence recall task (experiment 2). Overall, second-generation immigrants, who first acquired Japanese at home and Brazilian during childhood (after age 4) showed a typical Brazilian pattern of result (and so did simultaneous bilinguals, who were exposed to both languages from birth on). In contrast, late bilinguals, who acquired their second language in adulthood, exhibited a pattern corresponding to their native language. In addition, an influence of the second language was observed in the explicit task of Exp. 1, but not in the implicit task used in Exp. 2, suggesting that second language experience affects mostly explicit or metalinguistic skills. These results are compared to other studies of phonological representations in adopted children or immigrants, and discussed in relation to the role of age of acquisition and sociolinguistic factors.

Does reading in shallow L1 orthography slow attrition of language-specific morphological structures?

This study looks at the relationship between L1 (Russian) attrition and L1 reading ability in Russian-English-speaking bilingual children. Ten Russian-English bilingual children and 10 adults participated in this study. Nine out of 10 children participants were born in the US and used L1 as their primary language of interaction within the family, but the intensity and the length of uninterrupted L1 exposure differed for each child. All participants were tested on perception (grammaticality judgement) and production (narrative) tasks to assess their sensitivity to and retention of the morphosyntactic structure of L1. All children showed some attrition of grammatical morphemes, specifically in the Russian systems of declension and conjugation; however, the degree of attrition correlated with reading ability in L1, i.e. children with L1 reading skills showed a lesser degree of attrition for some language-specific morphosyntactic structures. This finding shows interdependence of oral and reading skills and points to the role reading in language with shallow orthography may play in preservation of L1 grammatical structures in oral language. The implications for the clinical applications are also discussed.

Preserved Implicit Knowledge of a Forgotten Childhood Language

Previous research suggests that a language learned during early childhood is completely forgotten when contact to that language is severed. In contrast with these findings, we report leftover traces of early language exposure in individuals in their adult years, despite a complete absence of explicit memory for the language. Specifically, native English individuals under age 40 selectively relearned subtle Hindi or Zulu sound contrasts that they once knew. However, individuals over 40 failed to show any relearning, and young control participants with no previous exposure to Hindi or Zulu showed no learning. This research highlights the lasting impact of early language experience in shaping speech perception, and the value of exposing children to foreign languages even if such exposure does not continue into adulthood.

Early Experience Predicts Later Plasticity for Face Processing

Research has shown that experience acquired in infancy dramatically affects face-discrimination abilities. Yet much less is known about whether face processing retains any flexibility after the 1st year of life. Here, we show that early experience with an individual infant face can modulate the recognition performance of 3-year-old children and the perceptual processes they use to recognize infant faces ( Experiment 1 ). Similar experience acquired in adulthood does not produce measurable effects ( Experiment 2 ). We also show that the effects of early-acquired experience with an infant face become dormant during development in the absence of continued experience ( Experiment 3 ) and can be reactivated in adulthood by reexposure to the original experience ( Experiment 2 ). Overall, the results indicate that early experience can preserve the face-processing system from the loss of plasticity that would otherwise take place between childhood and adulthood.

Salvaging a Childhood Language

Childhood experience with a language seems to help adult learners speak it with a more native-like accent. Can analogous benefits be found beyond phonology? This study focused on adult learners of Spanish who had spoken Spanish as their native language before age 7 and only minimally, if at all, thereafter until they began to re-learn Spanish around age 14 years. They were compared with native speakers, childhood overhearers, and typical late-second-language (L2)-learners of Spanish. Both childhood speakers and overhearers spoke Spanish with a more native-like accent than typical late-L2-learners. On grammar measures, childhood speakers-although far from native-like-reliably outperformed childhood overhearers as well as typical late-L2-learners. These results suggest that while simply overhearing a language during childhood could help adult learners speak it with a more native-like phonology, speaking a language regularly during childhood could help re-learners use it with more native-like grammar as well as phonology.

Cultural and linguistic influence on brain organization for language and possible consequences for dyslexia: a review

Current neuroimaging and neurophysiologic techniques have substantially increased our possibilities to study processes related to various language functions in the intact human brain. Learning to read and write influences the functional organization of the brain. What is universal and what is specific in the languages of the world are important issues. Most studies on healthy bilinguals indicate that essentially the same neural mechanisms are used for first and second languages, albeit with some linguistic and cultural influences related to speech and writing systems, particularly between alphabetical and nonalphabetical languages. Proficiency, age of acquisition, and amount of exposure can affect the cerebral representations of the languages. Accumulating data support the important role of working memory for acquiring high proficiency in the reading of native and second languages. It is proposed that longitudinal studies on second language acquisition are essential and that the specific problems related to second language learning in dyslexic children should have high priority.

Infant speech perception bootstraps word learning

By their first birthday, infants can understand many spoken words. Research in cognitive development has long focused on the conceptual changes that accompany word learning, but learning new words also entails perceptual sophistication. Several developmental steps are required as infants learn to segment, identify and represent the phonetic forms of spoken words, and map those word forms to different concepts. We review recent research on how infants' perceptual systems unfold in the service of word learning, from initial sensitivity for speech to the learning of language-specific sound patterns. Building on a recent theoretical framework and emerging new methodologies, we show how speech perception is crucial for word learning, and suggest that it bootstraps the development of a separate but parallel phonological system that links sound to meaning.

Speech perception as a window for understanding plasticity and commitment in language systems of the brain

In this article, we provide a critical review of the literature on speech perception and phonological processing in infancy, and in populations with different experiential histories as a window to understanding how the notion of critical periods might apply to the acquisition of one part of language: the sound system. We begin by suggesting the use of the term "optimal period" because (a) both the onset (opening) and offset (closing) of openness to experience is variable rather than absolute and (b) phonological acquisition involves the emergence of a series of nested capabilities, each with its own sensitive period and each best explained at one of several different levels of specificity. In support, we cite evidence suggesting that to fully understand plasticity and commitment in phonological acquisition, it is necessary to consider not only the biological and experiential factors which may contribute to the onset and the offset of openness to experience but also how the sequentially developing parts of phonology constrain and direct development. In summary, we propose a nested, cascading model wherein biology, experience, and functional use each contribute.

Early language acquisition: cracking the speech code

Infants learn language with remarkable speed, but how they do it remains a mystery. New data show that infants use computational strategies to detect the statistical and prosodic patterns in language input, and that this leads to the discovery of phonemes and words. Social interaction with another human being affects speech learning in a way that resembles communicative learning in songbirds. The brain's commitment to the statistical and prosodic patterns that are experienced early in life might help to explain the long-standing puzzle of why infants are better language learners than adults. Successful learning by infants, as well as constraints on that learning, are changing theories of language acquisition.

Production benefits of childhood overhearing

The current study assessed whether overhearing Spanish during childhood helps later Spanish pronunciation in adulthood. Our preliminary report based on a subset of the data [Au et al., Psychol. Sci. 13, 238-243 (2002)] revealed that adults who overheard Spanish during childhood had better Spanish pronunciation, but not better morphosyntax, than adult learners of Spanish who had no childhood experience with Spanish. We now present data from the full sample with additional morphosyntax and pronunciation assessments, as well as measures to help rule out possible confounding prosodic factors such as speech rate, phrasing, and stress placement. Three groups of undergraduates were compared: 15 Spanish-English bilinguals (native Spanish speakers), 15 late learners of Spanish who overheard Spanish during childhood (childhood overhearers), 15 late learners of Spanish who had no regular experience with Spanish until middle or high school (typical late L2 learners). Results confirmed a pronunciation advantage for the childhood overhearers over the typical late L2 learners on all measures: phonetic analyses (VOT and degree of lenition), accent ratings (phoneme and story production), but no benefit in morphosyntax. Importantly, the pronunciation advantage did not seem attributable to prosodic factors. These findings illustrate the specificity of overhearers' advantage to phonological production.