Effects of preceding context on the voice-onset-time category boundary.

The category boundary on a voice-onset-time (VOT) continuum ranging from bin to pin shifts when the stimuli are preceded by different carrier phrases. By using a variety of precursor phrases, by varying the temporal interval between precursor and test word, and by selectively eliminating either voicing information or spectral structure from the precursors, the present experiments show that the context effect is caused by the presence or absence of voicing in the precursor's final segment. The effect decreases with temporal separation but persists over several seconds. In addition, the "baseline" VOT boundary for isolated test words interspersed in a test sequence shifts depending on what precursor stimuli occur in the same sequence. The perception of VOT thus seems to be sensitive to both close and distant manifestations of laryngeal activity, always in an assimilative fashion, which suggests an integrative perceptual mechanism with a long time constant.