Performance on a test of categorical perception of speech in normal and communication disordered children

Abstract

A categorical perception paradigm was administered to a group of communication disordered children (mean age 7–0) divided into articulation, language, and articulation/language deficit subgroups and to a matched control group (mean age 6–11). The purpose was to assess the relationship between production deficits and speech perception abilities. Subjects were required to identify and discriminate bilabial stop consonants /ba/ and /pa/ from a synthetic series varying in 10 ms steps along a voice onset time continuum. Dependent variables analyzed were mean and variability data concerning phoneme boundary, boundary width, and correlations between predicted and obtained discrimination functions. Identification of end point stimuli were highly reliable for both groups (94–99% accuracy). Identification and discrimination functions for the two groups did not differ significantly in terms of mean values, but rather in variability. Standard deviation values for phoneme boundary and boundary width were two to six times greater in the disordered group than the normal group. The disordered group showed a greater discrepancy between predicted and obtained peak discrimination levels. Group results are tentatively interpreted as showing a moderate perceptual deficit in the communication disordered children of this study while more severe deficits are only observed upon examining individual cases.