Perceptual processing of multiple cues and contexts: effects of following vowel upon stop consonant voicing

Abstract

Variations in vowel context affect values of the acoustical variables that function as perceptual cues for the voicing distinction in initial stop consonants in English. Processing these context-dependent variations is a basic problem in speech perception. Of the several acoustical correlates of voicing that may be considered cues, two major ones are examined here, previously conflated in the Voice Onset Time concept: the first is the time from the burst to the first voicing pulse and is measured as the separation of these two events; the second is the relative position in the formant transition frame at which voicing onsets and is measured as the amount of voiced first formant (F1) transition. An experiment is reported which shows that for velar stops before /a/ both cues play a role in voicing perception although the transition cue is dominant. For velar stops before /i/, where no F1 transition occurs, the separation cue appears more important than it does in /a/ context. Consideration of these results points to the need to distinguish between contextual adjustments involving a simple boundary shift and those involving a reweighting of cues according to context. The two cues used here appear to be of different types with attendant differences in the effects they generate in perception experiments. In particular a sophisticated view of the processing of different cues may be necessary to give an account of adaptation in the voicing feature in experiments where the percentage of voiced or unvoiced responses is modified following repeated exposure to a stimulus with a distinct value of the feature.