Stimulus control analysis of language disorders: A study of substitution between voiced and unvoiced consonants

This study attempted to analyze defective stimulus control relations underlying persistent substitution between voiced and unvoiced consonants in the speech and writing of two children. A series of 20 tests was administered repeatedly. Some tests consisted of matching-to-sample tasks, with dictated words, printed words, or pictures as samples. Comparison stimuli were arranged in pairs of printed words or pictures, such that the only difference in their corresponding spoken words was the voicing of one consonant phoneme. In other tests, a stimulus (dictated word, printed word, or picture) was presented, and the subject was required to emit an oral response (repeat the dictated word, read the printed word, or name the picture) or a written response (write to dictation, copy the word, or write a picture name). Other tests required the subjects to make a same/different distinction in pairs of dictated words that did or did not differ in the voicing of a single phoneme. Results showed distinct deficit profiles for each subject, consisting of patterns of defective stimulus control relations. The subjects were able, however, to distinguish between voiced and unvoiced sounds and to produce these sounds.