The role of coarticulatory effects in the perception of fricatives by children and adults.

Adult listeners are sensitive to the acoustic variations that result from a speaker's coarticulation (or coproduction) of phonetic segments. The present study charted the development of such sensitivity in young children by examining their responses to coarticulatory effects in fricative-vowel syllables. Children, at each of the ages 3, 4, 5, and 7 years, and adults identified tokens from a synthetic /sh/-/s/ continuum followed by one of four natural vocalic portions: /i/ and /u/, produced with transitions appropriate for either /sh/ or /s/. Children demonstrated larger shifts in fricative phoneme boundaries as a function of vocalic transition than did adults, but relatively smaller shifts as a function of vowel quality. Responses were less consistent for children than for adults, and differences between children and adults decreased as children increased in age. Overall, these results indicate that perceptual sensitivity to certain coarticulatory effects is present at as young as 3 years of age. Moreover, the decrease in the sensitivity to vocalic transitions with age suggests that, contrary to a commonly held view, the perceptual organization of speech may become more rather than less segmental as the child develops.