Perceptual Categorization and Consistency of Synthesized /r-w/ Continua by Adults, Normal Children and /r/-Misarticulating Children

The purpose of this study was to determine if children who misarticulate /r/ differ from normal children and adults in the perception of sound features that are produced correctly and incorrectly. Children with normal articulation, children who produced /r/ misarticulations, and adults listened to synthesized child and adult /r-w/ continua in two separate sessions, and to an adult /b-w/ control continuum in one session. Perception was evaluated on the basis of measures of phonetic boundary location and the consistency of response to each stimulus in a continuum. The /r/-misarticulating children were found to be significantly less consistent than child and adult controls in responding to the /r-w/ stimuli. Moreover, consistency scores were significantly higher for the adult continuum than for the child continuum. The performance of children was different from that of adults. Due to inconsistent performance, boundaries could not be computed for /r/-misarticulating children, but it was found that the boundaries for children in the control group were closer to the /r/-end of the continuum than those for adults. In the case of the /b-w/ continuum, it was found that /r/-misarticulating children were significantly less consistent than adults. The phonetic boundaries of children were significantly closer to the /b/-end of the continuum than the boundary for adults. Thus, the results reveal that variability in stimulus response was influenced primarily by the productive ability of the subjects, whereas differences in stimulus categorization were influenced by the age of the subjects. The perceptual variability was most clearly reflected by responses to stimuli produced incorrectly, whereas categorization differences extended to sounds produced correctly.