The Development of Phonetic Perception

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My research program examines the development of speech perception on the level of phonetic segments (vowels and consonants). The broad objective is to fully portray perceptual biases that infants display in response to speech, explain how and when these perceptual biases form in development, and understand their role in the acquisition of spoken language. The research proposed here focuses on two well-established perceptual biases. In Studies 1 and 2, we investigate the focal vowel bias. This bias demonstrates our exquisite human sensitivity to the way that articulatory movements shape the physical speech signal, and is well documented in adults and 6- to 12-month-olds. In Study 1, we will measure the focal vowel bias (using auditory vowels) in 4 age groups (newborns, 2, 4 as, and expand our knowledge on how infants integrate speech information across different sensory modalities. In Studies 3 and 4 we investigate the infant talker bias, which is our recent, ground breaking discovery that pre-babbling infants (4 - 6 months) prefer to listen to vowel sounds that have the vocal properties of an infant talker over vowels produced by an adult. In study 3, we will measure the infant talker bias in 4 younger age groups (newborns, 2, 4 s own vocalizations in shaping this bias. In study 4, we will examine whether specific infant responses are induced more effectively by listening to infant speech than to adult speech sounds. While pre-babbling infants listen to vowels sounds, we will record their vocalizations and mouth movements and also measure changes in their heart rate (to index attention) and facial muscles (to index smiling). We will also record infant tongue movements using a new, infant-friendly ultrasound recording interface. Evidence that infant speech is a potent stimulus for provoking specific infant behaviors would have significant theoretical and practical implications. This outcome would indicate that access to infant speech has a very broad and meaningful impact - influencing receptive, expressive, and motivational aspects of speech development. The new ultrasound interface will also have a significant impact beyond the present work, by allowing us to explore uncharted aspects of early articulatory development.