Monolingual, bilingual, trilingual: Infants’ language experience influences the development of a word-learning heuristic

How infants learn new words is a fundamental puzzle in language acquisition. To guide their word learning, infants exploit systematic word-learning heuristics that allow them to link new words to likely referents. By 17 months, infants show a tendency to associate a novel noun with a novel object rather than a familiar one, a heuristic known as disambiguation. Yet, the developmental origins of this heuristic remain unknown. We compared disambiguation in 17 to 18-month-old infants from different language backgrounds to determine whether language experience influences its development, or whether disambiguation instead emerges as a result of maturation or social experience. Monolinguals showed strong use of disambiguation, bilinguals showed marginal use, and trilinguals showed no disambiguation. The number of languages being learned, but not vocabulary size, predicted performance. The results point to a key role for language experience in the development of disambiguation, and help to distinguish among theoretical accounts of its emergence

Language and the Newborn Brain: Does Prenatal Language Experience Shape the Neonate Neural Response to Speech?

Previous research has shown that by the time of birth, the neonate brain responds specially to the native language when compared to acoustically similar non-language stimuli. In the current study, we use near-infrared spectroscopy to ask how prenatal language experience might shape the brain response to language in newborn infants. To do so, we examine the neural response of neonates when listening to familiar versus unfamiliar language, as well as to non language stimuli. Twenty monolingual English-exposed neonates aged 0–3 days were tested. Each infant heard low-pass filtered sentences of forward English (familiar language), forward Tagalog (unfamiliar language), and backward English and Tagalog (non-language). During exposure, neural activation was measured across 12 channels on each hemisphere. Our results indicate a bilateral effect of language familiarity on neonates’ brain response to language. Differential brain activation was seen when neonates listened to forward Tagalog (unfamiliar language) as compared to other types of language stimuli. We interpret these results as evidence that the prenatal experience with the native language gained in utero influences how the newborn brain responds to language across brain regions sensitive to speech processing

Auditory Perception of Self-Similarity in Water Sounds

Many natural signals, including environmental sounds, exhibit scale-invariant statistics: their structure is repeated at multiple scales. Such scale-invariance has been identified separately across spectral and temporal correlations of natural sounds (Clarke and Voss, 1975; Attias and Schreiner, 1997; Escabi et al., 2003; Singh and Theunissen, 2003). Yet the role of scale-invariance across overall spectro-temporal structure of the sound has not been explored directly in auditory perception. Here, we identify that the acoustic waveform from the recording of running water is a self-similar fractal, exhibiting scale-invariance not only within spectral channels, but also across the full spectral bandwidth. The auditory perception of the water sound did not change with its scale. We tested the role of scale-invariance in perception by using an artificial sound, which could be rendered scale-invariant. We generated a random chirp stimulus: an auditory signal controlled by two parameters, Q, controlling the relative, and r, controlling the absolute, temporal structure of the sound. Imposing scale-invariant statistics on the artificial sound was required for its perception as natural and water-like. Further, Q had to be restricted to a specific range for the sound to be perceived as natural. To detect self-similarity in the water sound, and identify Q, the auditory system needs to process the temporal dynamics of the waveform across spectral bands in terms of the number of cycles, rather than absolute timing. We propose a two-stage neural model implementing this computation. This computation may be carried out by circuits of neurons in the auditory cortex. The set of auditory stimuli developed in this study are particularly suitable for measurements of response properties of neurons in the auditory pathway, allowing for quantification of the effects of varying the statistics of the spectro-temporal statistical structure of the stimulus

Lexicon Structure and the Disambiguation of Novel Words: Evidence from Bilingual Infants

In ambiguous word learning situations, infants can use systematic strategies to determine the referent of a novel word. One such heuristic is disambiguation. By age 16-18 months, monolinguals infer that a novel noun refers to a novel object rather than a familiar one (Halberda, 2003), while at the same age bilinguals and trilinguals do not reliably show disambiguation (Byers-Heinlein & Werker, 2009; Houston-Price, Caloghiris, & Raviglione, 2010). It has been hypothesized that these results reflect a unique aspect of the bilingual lexicon: bilinguals often know many translation equivalents, cross-language synonyms such as English dog and Mandarin gǒu. We studied the role of vocabulary knowledge in the development of disambiguation by relating 17-18 month-old English-Chinese bilingual infants’ performance on a disambiguation task to the percentage of translation equivalents in their comprehension vocabularies. Those bilingual infants who understood translation equivalents for more than half the words in their vocabularies did not show disambiguation, while infants who knew a smaller proportion of translation equivalents showed disambiguation just as same-aged monolinguals do. These results demonstrate that the structure of the developing lexicon plays a key role in infants’ use of disambiguation

Bilingual beginnings as a lens for theory development: PRIMIR in focus

PRIMIR (Processing Rich Information from Multidimensional Interactive Representations; Werker & Curtin, 2005; Curtin & Werker, 2007) is a framework that encompasses the bidirectional relations between infant speech perception and the emergence of the lexicon. Here, we expand its mandate by considering infants growing up bilingual. We argue that, just like monolinguals, bilingual infants have access to rich information in the speech stream and by the end of their first year, they establish not only language-specific phonetic category representations, but also encode and represent both sub-phonetic and indexical detail. Perceptual biases, developmental level, and task demands work together to influence the level of detail used in any particular situation. In considering bilingual acquisition, we more fully elucidate what is meant by task demands, now understood both in terms of external demands imposed by the language situation, and internal demands imposed by the infant (e.g. different approaches to the same apparent task taken by infants from different backgrounds). In addition to the statistical learning mechanism previously described in PRIMIR, the necessity of a comparison-contrast mechanism is discussed. This refocusing of PRIMIR in the light of bilinguals more fully explicates the relationship between speech perception and word learning in all infants

Bilingual beginnings to learning words

At the macrostructure level of language milestones, language acquisition follows a nearly identical course whether children grow up with one or with two languages. However, at the microstructure level, experimental research is revealing that the same proclivities and learning mechanisms that support language acquisition unfold somewhat differently in bilingual versus monolingual environments. This paper synthesizes recent findings in the area of early bilingualism by focusing on the question of how bilingual infants come to apply their phonetic sensitivities to word learning, as they must to learn minimal pair words (e.g. ‘cat’ and ‘mat’). To this end, the paper reviews antecedent achievements by bilinguals throughout infancy and early childhood in the following areas: language discrimination and separation, speech perception, phonetic and phonotactic development, word recognition, word learning and aspects of conceptual development that underlie word learning. Special consideration is given to the role of language dominance, and to the unique challenges to language acquisition posed by a bilingual environment

The roots of bilingualism in newborns

The first steps towards bilingual language acquisition have already begun at birth. When tested on their preference for English versus Tagalog, “monolingual” newborns, whose mothers spoke only English during pregnancy, showed a robust preference for English. In contrast, “bilingual” newborns, whose mothers spoke both English and Tagalog regularly during pregnancy, showed equal preference for both languages. A group of Chinese-English bilinguals showed an intermediate pattern of preference. Preference for two languages does not suggest confusion between them, however. Study 2 showed that both English monolinguals and Tagalog-English bilinguals could discriminate English from Tagalog. The same perceptual and learning mechanisms that support acquisition in a monolingual environment thus also naturally support bilingual acquisition