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.
In this article, I present a selective review of research on speech perception development and its relation to reference, word learning, and other aspects of language acquisition, focusing on the ...empirical and theoretical contributions that have come from my laboratory over the years. Discussed are the biases infants have at birth for processing speech, the mechanisms by which universal speech perception becomes attuned to the properties of the native language, and the extent to which changing speech perception sensitivities contribute to language learning. These issues are reviewed from the perspective of both monolingual and bilingual learning infants. Two foci will distinguish this from my previous reviews: first and foremost is the extent to which contrastive meaning and referential intent are not just shaped by, but also shape, changing speech perception sensitivities, and second is the extent to which infant speech perception is multisensory and its implications for both theory and methodology.
In this article, we begin with a summary of the evidence for perceptual narrowing for various aspects of language (e.g., vowel and consonant contrasts, tone languages, visual language, sign language) ...and of faces (e.g., own species, own race). We then consider possible reasons for the apparent differences in the timing of narrowing (e.g., apparently earlier for own race than for own species). Throughout we consider whether the evidence fits a model of maintenance/loss or is better characterized as enhancement/attunement to exposed categories. Finally, we consider evidence on the malleability of the timing and its implications for the role of endogenous factors versus learning in controlling when narrowing occurs. Overall, the comparison across domains revealed many similarities but also striking differences which lead to suggestions for future research.
Critical period regulation across multiple timescales Reh, Rebecca K.; Dias, Brian G.; Nelson, Charles A. ...
Proceedings of the National Academy of Sciences - PNAS,
09/2020, Letnik:
117, Številka:
38
Journal Article
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Brain plasticity is dynamically regulated across the life span, peaking during windows of early life. Typically assessed in the physiological range of milliseconds (real time), these trajectories are ...also influenced on the longer timescales of developmental time (nurture) and evolutionary time (nature), which shape neural architectures that support plasticity. Properly sequenced critical periods of circuit refinement build up complex cognitive functions, such as language, from more primary modalities. Here, we consider recent progress in the biological basis of critical periods as a unifying rubric for understanding plasticity across multiple timescales. Notably, the maturation of parvalbumin-positive (PV) inhibitory neurons is pivotal. These fast-spiking cells generate gamma oscillations associated with critical period plasticity, are sensitive to circadian gene manipulation, emerge at different rates across brain regions, acquire perineuronal nets with age, and may be influenced by epigenetic factors over generations. These features provide further novel insight into the impact of early adversity and neurodevelopmental risk factors for mental disorders.
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.
•Reflections on Werker & Tees, 1984, and related work on perceptual reorganization.•Evidence for perceptual attunement, and other patterns of change.•Role of distributional and word-based learning mechanisms in perceptual attunement.•Evidence for critical periods in speech perception development.
The Roots of Bilingualism in Newborns Byers-Heinlein, Krista; Burns, Tracey C.; Werker, Janet F.
Psychological science,
03/2010, Letnik:
21, Številka:
3
Journal Article
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The first steps toward bilingual language acquisition have already begun at birth. When tested on their preference for English versus Tagalog, newborns whose mothers spoke only English during ...pregnancy showed a robust preference for English. In contrast, newborns whose mothers spoke both English and Tagalog regularly during pregnancy showed equal preference for both languages. A group of newborns whose mothers had spoken both Chinese and English showed an intermediate pattern of preference for Tagalog over English. Preference for two languages does not suggest confusion between them, however. Study 2 showed that both English monolingual newborns and Tagalog-English bilingual newborns could discriminate English from Tagalog. The same perceptual and learning mechanisms that support acquisition in a monolingual environment thus also naturally support bilingual acquisition.
A central problem in language acquisition is how children effortlessly acquire the grammar of their native language even though speech provides no direct information about underlying structure. This ...learning problem is even more challenging for dual language learners, yet bilingual infants master their mother tongues as efficiently as monolinguals do. Here we ask how bilingual infants succeed, investigating the particularly challenging task of learning two languages with conflicting word orders (English: eat an apple versus Japanese: ringo-wo taberu 'apple.acc eat'). We show that 7-month-old bilinguals use the characteristic prosodic cues (pitch and duration) associated with different word orders to solve this problem. Thus, the complexity of bilingual acquisition is countered by bilinguals' ability to exploit relevant cues. Moreover, the finding that perceptually available cues like prosody can bootstrap grammatical structure adds to our understanding of how and why infants acquire grammar so early and effortlessly.
One of the central themes in the study of language acquisition is the gap between the linguistic knowledge that learners demonstrate, and the apparent inadequacy of linguistic input to support ...induction of this knowledge. One of the first linguistic abilities in the course of development to exemplify this problem is in speech perception: specifically, learning the sound system of one’s native language. Native-language sound systems are defined by meaningful contrasts among words in a language, yet infants learn these sound patterns before any significant numbers of words are acquired. Previous approaches to this learning problem have suggested that infants can learn phonetic categories from statistical analysis of auditory input, without regard to word referents. Experimental evidence presented here suggests instead that young infants can use visual cues present in word-labeling situations to categorize phonetic information. In Experiment 1, 9-month-old English-learning infants failed to discriminate two non-native phonetic categories, establishing baseline performance in a perceptual discrimination task. In Experiment 2, these infants succeeded at discrimination after watching contrasting visual cues (i.e., videos of two novel objects) paired consistently with the two non-native phonetic categories. In Experiment 3, these infants failed at discrimination after watching the same visual cues, but paired inconsistently with the two phonetic categories. At an age before which memory of word labels is demonstrated in the laboratory, 9-month-old infants use contrastive pairings between objects and sounds to influence their phonetic sensitivity. Phonetic learning may have a more functional basis than previous statistical learning mechanisms assume: infants may use cross-modal associations inherent in social contexts to learn native-language phonetic categories.
Sensorimotor influences on speech perception in infancy Bruderer, Alison G.; Danielson, D. Kyle; Kandhadai, Padmapriya ...
Proceedings of the National Academy of Sciences - PNAS,
11/2015, Letnik:
112, Številka:
44
Journal Article
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The influence of speech production on speech perception is well established in adults. However, because adults have a long history of both perceiving and producing speech, the extent to which the ...perception–production linkage is due to experience is unknown. We addressed this issue by asking whether articulatory configurations can influence infants’ speech perception performance. To eliminate influences from specific linguistic experience, we studied preverbal, 6-mo-old infants and tested the discrimination of a nonnative, and hence never-before-experienced, speech sound distinction. In three experimental studies, we used teething toys to control the position and movement of the tongue tip while the infants listened to the speech sounds. Using ultrasound imaging technology, we verified that the teething toys consistently and effectively constrained the movement and positioning of infants’ tongues. With a looking-time procedure, we found that temporarily restraining infants’ articulators impeded their discrimination of a nonnative consonant contrast but only when the relevant articulator was selectively restrained to prevent the movements associated with producing those sounds. Our results provide striking evidence that even before infants speak their first words and without specific listening experience, sensorimotor information from the articulators influences speech perception. These results transform theories of speech perception by suggesting that even at the initial stages of development, oral–motor movements influence speech sound discrimination. Moreover, an experimentally induced “impairment” in articulator movement can compromise speech perception performance, raising the question of whether long-term oral–motor impairments may impact perceptual development.
The nature and origin of the human capacity for acquiring language is not yet fully understood. Here we uncover early roots of this capacity by demonstrating that humans are born with a preference ...for listening to speech. Human neonates adjusted their high amplitude sucking to preferentially listen to speech, compared with complex non‐speech analogues that controlled for critical spectral and temporal parameters of speech. These results support the hypothesis that human infants begin language acquisition with a bias for listening to speech. The implications of these results for language and communication development are discussed.
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