Effect of selective adaptation on the discrimination of small differences in voice onset time (VOT)

The effect of selective adaptation (i.e., listening to a rapidly repeated syllable) on the discrimination of voiceless stimuli which differ only in VOT was investigated. In an AX procedure under conditions of minimal stimulus uncertainty, subjects in the unadapted state were able to discriminate (d′=1)small (5 msec) differences in the VOT of stimuli from the voiceless end of a /ba/—/pa/ continuum. Control experiments showed this discrimination was not based on memorization of the aspiration noise waveform, and that subjects could represent small differences in VOT in long‐term memory. Adaptation depressed discrimination slightly, showing that adaptation can affect a perceptual task which does not depend on phonetic categorization. The data were not precise enough to indicate whether adaptation affected a level sensitive to the acoustic similarity of the adapting and test stimuli or to the relationship of the adapting stimulus to the phonetic category.