The development of phonetic perception

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This research program explores the development of speech perception in infancy through investigations that focus on vowel perception. Our goal is to fully portray vowel perception biases that young infants display in response to speech, explain how and when these perceptual biases form in development, and establish their role in the acquisition of spoken language. In pursuing these goals we will test and elaborate a new conceptual model, the Natural Referent Vowel (NRV) framework. According to this view, vowels with specific articulatory-acoustic properties (which also define the peripheral vowels in a traditional vowel space) act a natural referents: they support and guide the development of vowel perception by attracting infant attention and establishing a stable frame of reference for the learner. Prior studies of infant listening preferences for different vowels support this view by showing that infants (4 to 12 months of age) have a strong perceptual bias favoring peripheral vowels. Study 1 will assess when (and how) this perceptual bias is initially formed in early infancy. We will compare 2-month-olds and newborns to assess the hypothesis that vowel perception biases emerge early in life via an interaction between infant neuro-auditory abilities and speech exposure. Studies 2 and 3 will test the NRV claim that peripheral vowels support the development of vowel perception and production. Study 2 tests the prediction that vowel perception biases also impact how babies perceive their own vocal patterns by examining infant listening preferences for vowels produced by an infant talker (using a new vowel synthesis tool). Study 3 will assess infant ability to recognize the same vowel produced by different talkers (adult, child, infant) to test the NRV prediction that vowel categorization skills develop in a stepwise, hierarchical manner such that peripheral vowel categories are acquired more easily and prior to non-peripheral vowel categories. This will be the first study to investigate how infants perceive infant-produced vocal signals. This approach is needed to understand how speaking and listening skills interact in infant speech development.