Properties of feature detectors for VOT: The voiceless channel of analysis

Abstract

Binaural adaptation was combined with a dichotic ear-monitoring task [in man] to estimate the output function of the voiceless detector sensitive to VOT [voice onset time] and to determine how this function is modified by selective adaptation. On each test trial a voiced stop was paried with one of a set of voiceless stops, which spanned a range of VOT values. The percentage of voiceless responses per pair, which reflects the number of correct voicing judgments on voiceless targets and the number of voiceless intrusions on voiced targets, was measured before and after adaptation with a voiced stimulus and a variety of voiceless stimuli. Before adaptation, the percentage of voiceless responses per pair systematically increased with an increase in the VOT value of the voiceless stimulus of the pair. Adaptation resulted in a shift in the percentage of voiceless responses per pair in the predicted direction, with progressively large shifts occurring for voiceless adapting stimuli with higher VOT values. Apparently the output of the detector is a graded signal whose magnitude is an increasing function of VOT value and adaptation depresses the entire output function from its preadaptation level, with the amount of depression determined by the extent to which the adapting stimulus excites the detector.