Interaction of multiple factors in the development of speech production

By A. Smith and L. Goffman

Language and motor processes co-develop in childhood, but generally language development and the maturation of speech motor control have been examined independently. Questions about language development have been framed in terms of linguistic theories and units, while the course of speech motor development has been examined in relation to indices of physical growth and neuromotor maturation. We have undertaken a large n, cross-sectional study of speech motor development in children aged 4 years through young adulthood. Also, in parallel, we have conducted a series of studies of small numbers of participants to address specific questions about the potential influences of linguistic units on speech motor output. We describe the results of these investigations of articulatory motor control and coordination. These studies explore links between speech motor control and a range of other variables, including orofacial structure size, prosodic demands, and syntactic complexity. We discuss how these results lead us to propose tighter links between language processing and speech motor control than earlier models would have suggested. Finally we suggest that there are multiple linguistic units which operate in both motor and linguistic domains.