ABSTRACT
From the infant's point of view, the task of sorting out the varied array of sounds directed toward him or her into a coherent set of signals appears to be a formidable one. The sources of variation in utterances produced by even the same speaker in the same context would appear to be overwhelming. The problem is only confounded when one considers the variations produced in noisy environments, by different adults of the same sex, by children and adults, or by males and females. Yet, somehow during the course of the first year of life, infants act as if they understand certain words, and a few months later are producing their own words. Perhaps, we should not be too surprised by this since similar feats of perceptual constancy appear to be presented in the visual domain (Day & McKenzie, 1973; Spelke, 1982), and even intermodally (Meltzoff, 1985; Rose, Gottfried, & Bridger, 1983). Nevertheless, the demonstration that invariance is found in other sensory modalities does not free us from the need to explain the instances of invariance that appear in connection with the infant's perception of speech sounds. Two speech perception phenomena would seem to require the infant's capacity to perceive an invariant relation across different tokens. The first is the well-known phenomenon of categorical perception; the second is the capacity to recognize the same utterances produced by different speakers. Both of these, phenomena have been the object of investigation in studies of infant speech perception. In what follows, we review briefly some of the major findings in the field of infant speech perception. We consider the possible mechanisms that might underlie the infant's basic capacities, and then discuss the ways in which these capacities might develop during the course of language acquisition.
