Comparison of speech discrimination in nonretarded and retarded listeners.

An adaptive psychophysical procedure was used to determine the articulation functions for nonretarded and retarded subjects using Kindergarten Phonetically Balanced stimulus words. Merits of this procedure are: (a) it is efficient since stimulus intensity levels are well-placed with respect to the measures being obtained, and (b) estimates of intrasubject variability can be obtained from one test session. The slope of the articulation function based on the pooled data from the nonretarded subject (3.5 percent/dB) was greater than the slope of the function from the retarded subjects (2.1 percent/dB). No significant differences in intrasubject variability between the two groups were discovered. It is not clear whether the reduced slope of the articulation function from the retarded subjects was due to a familiarity factor and/or to a basic difference in auditory processing characteristics. Work is continuing in an attempt to clarify this issue.