On categorizing aphasic speech errors.

Acoustic studies of voice-onset-time in aphasics' speech suggest that fluent aphasics' errors are misselected phonemic targets whereas nonfluent aphasics' errors are of articulatory origin. However, we must be cautious when extrapolating a theory from only one measure of articulation. In this experiment, I examined utterances produced by five fluent aphasics, five nonfluent aphasics and two controls. First, the voice-onset-time findings were replicated. Second, I examined the duration of vowels preceding word-final stop consonants as an index of the consonant's voicing category. The pattern of voice-onset-times produced did not predict the pattern of vowel durations. Thus, voice-onset-time cannot be used to characterize more generally the output of the speaker.