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Abstract
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.