Impact of second-language experience in infancy: brain measures of first- and second-language speech perception.

Language experience 'narrows' speech perception by the end of infants' first year, reducing discrimination of non-native phoneme contrasts while improving native-contrast discrimination. Previous research showed that declines in non-native discrimination were reversed by second-language experience provided at 9-10 months, but it is not known whether second-language experience affects first-language speech sound processing. Using event-related potentials (ERPs), we examined learning-related changes in brain activity to Spanish and English phoneme contrasts in monolingual English-learning infants pre- and post-exposure to Spanish from 9.5-10.5 months of age. Infants showed a significant discriminatory ERP response to the Spanish contrast at 11 months (post-exposure), but not at 9 months (pre-exposure). The English contrast elicited an earlier discriminatory response at 11 months than at 9 months, suggesting improvement in native-language processing. The results show that infants rapidly encode new phonetic information, and that improvement in native speech processing can occur during second-language learning in infancy.

Cognitive control factors in speech perception at 11 months.

The development of speech perception during the 1st year reflects increasing attunement to native language features, but the mechanisms underlying this development are not completely understood. One previous study linked reductions in nonnative speech discrimination to performance on nonlinguistic tasks, whereas other studies have shown associations between speech perception and vocabulary growth. The present study examined relationships among these abilities in 11-month-old infants using a conditioned head-turn test of native and nonnative speech sound discrimination, nonlinguistic object-retrieval tasks requiring attention and inhibitory control, and the MacArthur-Bates Communicative Development Inventory (L. Fenson et al., 1993). Native speech discrimination was positively linked to receptive vocabulary size but not to the cognitive control tasks, whereas nonnative speech discrimination was negatively linked to cognitive control scores but not to vocabulary size. Speech discrimination, vocabulary size, and cognitive control scores were not associated with more general cognitive measures. These results suggest specific relationships between domain-general inhibitory control processes and the ability to ignore variation in speech that is irrelevant to the native language and between the development of native language speech perception and vocabulary.

Social Interaction in Infants' Learning of Second-Language Phonetics: An Exploration of Brain-Behavior Relations.

Infants learn phonetic information from a second language with live-person presentations, but not television or audio-only recordings. To understand the role of social interaction in learning a second language, we examined infants' joint attention with live, Spanish-speaking tutors and used a neural measure of phonetic learning. Infants' eye-gaze behaviors during Spanish sessions at 9.5-10.5 months of age predicted second-language phonetic learning, assessed by an event-related potential measure of Spanish phoneme discrimination at 11 months. These data suggest a powerful role for social interaction at the earliest stages of learning a new language.

Lexical and grammatical associations in sequential bilingual preschoolers.

PURPOSE: The authors investigated potential relationships between traditional linguistic domains (words, grammar) in the first (L1) and second (L2) languages of young sequential bilingual preschool children. METHOD: Participants were 19 children, ages 2;11 (years;months) to 5;2 (M = 4;3) who began learning Hmong as the L1 from birth and English as the L2 during early childhood. Measures were the number of different words (NDW) and mean length of utterance (MLU) produced during a story retell task and scores on picture identification, an independent measure of receptive vocabulary. Correlations were conducted to determine relationships among measures. RESULTS: In English, there were robust positive relationships between MLU and lexical measures (NDW, Picture Identification). In Hmong, more modest cross-domain associations were evident between lexical measures and MLU. There were positive cross-language links for NDW but more limited cross-domain correspondences between the L1 and the L2. CONCLUSIONS: In English, relationships between words and grammar were similar to those found in previous studies with monolingual and simultaneous bilingual toddlers. Weaker cross-domain associations in the L1 may reflect participants' greater development in Hmong or typological differences between the L1 and the L2.

Phonetic learning as a pathway to language: new data and native language magnet theory expanded (NLM-e).

Infants' speech perception skills show a dual change towards the end of the first year of life. Not only does non-native speech perception decline, as often shown, but native language speech perception skills show improvement, reflecting a facilitative effect of experience with native language. The mechanism underlying change at this point in development, and the relationship between the change in native and non-native speech perception, is of theoretical interest. As shown in new data presented here, at the cusp of this developmental change, infants' native and non-native phonetic perception skills predict later language ability, but in opposite directions. Better native language skill at 7.5 months of age predicts faster language advancement, whereas better non-native language skill predicts slower advancement. We suggest that native language phonetic performance is indicative of neural commitment to the native language, while non-native phonetic performance reveals uncommitted neural circuitry. This paper has three goals: (i) to review existing models of phonetic perception development, (ii) to present new event-related potential data showing that native and non-native phonetic perception at 7.5 months of age predicts language growth over the next 2 years, and (iii) to describe a revised version of our previous model, the native language magnet model, expanded (NLM-e). NLM-e incorporates five new principles. Specific testable predictions for future research programmes are described.

Grammatical processing without semantics? An event-related brain potential study of preschoolers using jabberwocky sentences.

Behavioral studies have demonstrated that children develop a nearly adult-like grammar between 36 and 42 months, but few studies have addressed how the child's brain processes semantic versus syntactic information. In previous research, Silva-Pereyra and colleagues showed that distinct event-related potentials (ERPs) are elicited by semantic and syntactic violations in sentences in children as young as 30, 36, and 48 months, following the patterns displayed by adults. In the current study, we examined ERPs to syntactic phrase structure violations in real and jabberwocky sentences in 36-month-old children. Jabberwocky sentences are sentences in which content (open-class) words are replaced by pseudowords while function (closed-class) words are retained. Results showed that syntactically anomalous real sentences elicited two positive ERP effects: left-distributed effects from 500 to 750 msec and 1050 to 1300 msec, whereas syntactically anomalous jabberwocky sentences elicited two negative ERP effects: a left-distributed effect from 750 to 900 msec and a later broadly distributed effect from 950 to 1150 msec. The results indicate that when preschoolers process real English sentences, ERPs resembling the positive effects previously reported for adults are noted, although at longer latencies and with broader scalp distributions. However, when preschoolers process jabberwocky sentences with altered lexical-semantic content, a negative-going ERP component similar to one typically associated with the extraction of meaning is noted.

Ties between the lexicon and grammar: cross-sectional and longitudinal studies of bilingual toddlers.

Studies using the English and Spanish MacArthur Communicative Development Inventories demonstrated that the grammatical abilities of 20-30-month-old bilingual children were related more strongly to same-language vocabulary development than to broader lexical-conceptual development or maturation. First, proportions of different word types in each language varied with same-language vocabulary size. Second, individual changes in predicate and closed class word proportion scores were linked to growth in same-language vocabulary but not to total conceptual vocabulary. Third, increases in English utterance length and English and Spanish sentence complexity were related to growth in same-language vocabulary but not to growth in conceptual vocabulary. Increases in Spanish utterance length were linked to growth in both Spanish vocabulary and conceptual vocabulary. Possible mechanisms underlying these patterns are considered.

Two languages, one developing brain: event-related potentials to words in bilingual toddlers.

Infant bilingualism offers a unique opportunity to study the relative effects of language experience and maturation on brain development, with each child serving as his or her own control. Event-related potentials (ERPs) to words were examined in 19- to 22-month-old English-Spanish bilingual toddlers. The children's dominant vs. nondominant languages elicited different patterns of neural activity in the lateral asymmetry of an early positive component (P100), and the latencies and distributions of ERP differences to known vs. unknown words from 200-400 and 400-600 ms. ERP effects also differed for 'high' and 'low' vocabulary groups based on total conceptual vocabulary scores. The results indicate that the organization of language-relevant brain activity is linked to experience with language rather than brain maturation.