Sensorimotor influences on speech perception in infancy

The multisensory nature of speech, and in particular, the modulatory influence of one’s own articulators during speech processing, is well established in adults. However, the origins of the sensorimotor influence on auditory speech perception are largely unknown, and require the examination of a population in which a link between speech perception and speech production is not well-defined; by studying preverbal infant speech perception, such early links can be characterized. Across three experimental chapters, I provide evidence that articulatory information selectively affects the perception of speech sounds in preverbal infants, using both neuroimaging and behavioral measures. In Chapter 2, I use a looking time procedure to show that in 6-month-old infants, articulatory information can impede the perception of a consonant contrast when the related articulator is selectively impaired. In Chapter 3, I use the high-amplitude suck (HAS) procedure to show that neonates are able to discriminate and exhibit memory for the vowels /u/ and /i/; however, the information from the infants’ articulators (a rounded lip shape) seems to only marginally affect behavior during the learning of these vowel sounds. In Chapter 4, I co-register HAS with a neuroimaging technique – Near Infrared Spectroscopy (NIRS) – and identify underlying neural networks in newborn infants that are sensitive to the sensorimotor-auditory match, in that the vowel which matches the lip shape (/u/) is processed differently than the vowel that is not related to the lip shape (/i/). Together, the experiments reported in this dissertation suggest that even before infants gain control over their articulators and speak their first words, their sensorimotor systems are interacting with their perceptual systems as they process auditory speech information.Arts, Faculty ofPsychology, Department ofGraduat