Time-shrinking: A discontinuity in the perception of auditory temporal patterns

Recent research at our laboratories in the field of human auditory time perception revealed that the duration of short empty time intervals (<～200 msec) is considerably underestimated if they are immediately preceded by shorter time intervals. Within a certain range, the amount of subjective time shrinking is a monotonous function of the preceding time interval: the shorter it is, the more it shrinks its successor. In the present study, the preceding interval was kept constant at 50 msec, and the following interval for which the duration had to be judged, varied from 40 to 280 msec. The results showed that at up to 100 msec, the perceived duration increased to a much lesser extent than did the objective duration. Beyond 120 msec, the perceived duration quickly increased and reached a veridical value at 160 msec. Such a sudden change of perceived duration in a temporal pattern in which the objective duration varies gradually indicates a typical example of categorical perception. We suggest that such a categorization of the time dimension might be a clue for processes of speech and music perception.