Impact of Speech Input on Speech Production Learning

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This research program is concerned with discovering the mechanisms that underly the emergence of speech motor control in the earliest stages of development, with a particular focus on adaptation to variable inputs. It has long been thought that all infants babbled in the same way due to severe constraints on speech motor control. Over the past ten years of NSERC-funded research we established that infants learning English, French or Arabic develop babbling with distinct vowel characteristics when measured acoustically. In this project I aim to illuminate the mechanism by which the speech input from adults influences the infant's vocal output. In one series of studies, vocal exchanges between mothers and infants will be recorded longitudinally at 6, 8, 10, 12 and 14 months. The vowel sounds in the mothers' and infants' speech will be described acoustically and the distributions of acoustic characteristics will be plotted in detail to reveal patterns of convergence within dyads and divergence across language groups as they emerge over time. Aspects of the moment-to-moment temporal patterning of infant and maternal vocalizations will be described. In a second series of studies the temporal pattern of vowel inputs will be manipulated relative to infant vocal outputs. These studies will allow us to test alternative hypotheses regarding potential mechanisms that might explain adaptation to acoustic characteristics of the speech input in infant vocal development. These studies will further our understanding of the normal processes by which the infant adapts their speech production to the ambient language environment and will also have implications for our understanding of delayed speech acquisition.