Speech Development

Abstract

Every natural language deploys a large lexicon, constructed by permutation and combination of a few dozen segments (consonants and vowels). Contrasts among these segments may be described in terms of a small number of phonetic features, defined by the coordinated actions of several more or less independent articulators (jaw, lips, tongue, velum, larynx). The task for a child learning to speak is to reproduce, or imitate, the patterns of articulatory gesture specified by the acoustic structures of the words heard. A capacity to imitate vocalizations is confined to a few species of songbird, certain marine mammals, and humans. That this capacity calls on specialized neural mechanisms in humans is further argued by the fact that the capacities both to perceive the phonetic structure of an unknown word and to speak at all are functions of the left cerebral hemisphere in most normal adults.