Our previous research on auditory time perception showed that the duration of empty time intervals shorter than about 250 ms can be underestimated hugely if they are immediately preceded by shorter time intervals. We named this illusion 'time-shrinking' (TS). This study comprises four experiments in which the preceding interval, t1, was followed by a standard interval, t2. When t1 < or = 200 ms, and t1 < or = t2, the underestimation of t2 came into view clearly. The absolute difference between t2 and t1 was the crucial factor for the illusion to appear. The underestimation increased when t2 increased from t1 to t1 + 65 ms, stayed at about 45 ms when t2 was between t1 + 65 ms and t1 + 95 ms, and disappeared suddenly when t2 exceeded t1 + 95 ms. This pattern of results was observed across all values of t1 < or = 200 ms. A model was fit to the data to elucidate the underlying process of the illusion. The model states that the perceived duration difference between t1 and t2 is reduced by cutting mental processing time for t2; in other words, that t2 assimilates to t1.

We present a new auditory illusion, the gap transfer illusion, supported by phenomenological and psychophysical data. In a typical situation, an ascending frequency glide of 2,500 msec with a temporal gap of 100 msec in the middle and a continuously descending frequency glide of 500 msec cross each other at their central positions. These glides move at the same constant speed in logarithmic frequency in opposite directions. The temporal gap in the long glide is perceived as if it were in the short glide. The same kind of subjective transfer of a temporal gap can take place also when the stimulus pattern is reversed in time. This phenomenon suggests that onsets and terminations of glide components behave as if they were independent perceptual elements. We also find that when two long frequency glides are presented successively with a short temporal overlap, a long glide tone covering the whole duration of the pattern and a short tone around the temporal middle can be perceived. To account for these results, we propose an event construction model, in which perceptual onsets and terminations are coupled to construct auditory events and the proximity principle connects these elements.

Recent research at our laboratories in the field of human auditory time perception revealed that the duration of short empty time intervals (less than approximately 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.

The solubility of zirconium(IV) hydrous oxide was measured in the hydrogen ion concentration (pH

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