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.

When two very short time intervals are presented serially by sound markers (in such a way that they share a common marker) the subject's duration judgments of the second time interval can be affected by the duration of the first interval. Such a conspicuous effect has not been reported in the literature. Standard empty time intervals of 120, 240, 480, and 720 msec were preceded by a neighboring empty time interval of various physical durations, and subjects adjusted a comparison empty time interval to the same subjective duration as these standards. We found clear underestimations of the standard duration when its physical duration was 120 msec. For example, when the preceding duration was 45 msec, the relative underestimation was about 40%. Because such a stable and remarkable underestimation appeared in a very simple situation, this phenomenon may be called a new illusion. Such an illusion did not appear when the time interval to be judged was succeeded by another time interval. At present we cannot explain the illusion, but in the general discussion we attempt to relate it to some findings in rhythm perception.

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 multiple-look notion holds that the difference limen (DL) decreases with multiple observations. We investigated this notion for temporal discrimination in isochronous sound sequences. In Experiment 1, we established a multiple-look effect when sequences comprised nine standard time intervals (S) followed by an increasing number of comparison time intervals (C), but no multiple-look effect when one trailing C interval was preceded by an increasing number of S intervals. In Experiment 2, we extended the design. There were four sequential conditions: (a) 9 leading S intervals followed by 1, 2, …, or 9 C-intervals; (b) 9 leading C intervals followed by 1, 2, …, or 9 S intervals; (c) 9 trailing C-intervals preceded by 1, 2, …, or 9 S-intervals; and (d) 9 trailing S-intervals preceded by 1, 2, …, or 9 C-intervals. Both the interval accretions before and after the tempo change caused multiple-look effects, irrespective of the time order of S and C. Complete deconfounding of the number of intervals before and after the tempo change was accomplished in Experiment 3. The multiple-look effect of interval accretion before the tempo change was twice as big as that after the tempo change. The diminishing returns relation between the DL and interval accretion could be described well by a reciprocal function.

It has previously been reported that the duration of short time intervals is conspicuously underestimated if they are preceded by shorter neighbouring time intervals. This illusion was called 'time shrinking' and it was argued that it strongly affects the perception of auditory rhythms. In the present study this supposition has been pursued in three experiments. In the first, temporal patterns consisting of two, three, and four intervals had to be judged for anisochrony, which was invoked by offsetting the last sound from its isochronous position. By a constant method, it was determined that the last sound of fast sequences (50 ms base interval) had to be delayed by about 30 ms in order for isochronous rhythms to be perceived. Another interesting finding was that for sound sequences with base intervals up to 200 ms it was the difference limen, rather than Weber's ratio, that was constant for anisochrony detection. In the second experiment, the temporal patterns comprised two intervals, presented serially or separately. The deviation of isochrony could be on either the first or the second interval. The data, gathered by an adaptive method, showed time shrinking to be effective even up to a base interval of 200 ms. The third experiment involved a constant method and anisochrony was implemented on the first interval of two interval patterns. Time shrinking affected perceived isochrony in sequences with base intervals of 50, 100, and 200 ms. It is argued that the paradoxical results of anisochrony detection can be explained in terms of time shrinking. Some anomalies of rhythm perception and production that are the result of time shrinking are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

In previous studies, we established an illusion of time perception that we called time-shrinking: an empty time interval, immediately preceded by a slightly shorter time interval, is underestimated. In the first experiment of the present study, we examined the perceived duration not only of the second interval (t2), but also of the first interval (tl). The empty time intervals tl and t2, making a total duration of 90,180, 360, or 720 ms, were presented such that the time ratio between them changed systematically. The points of subjective equality of tl and t2 were established by the method of adjustment. In the patterns typically susceptible to timeshrinking, that is, in which t2 was underestimated, tl was perceived almost vertically. In the second experiment, listeners had to bisect an empty duration of 180 ms, marked by sound bursts. The bisecting sound marker was positioned closer to the initial marker than to the final one. Thus, tl had to be shorter than t2 in order for a regular pattern to be perceived. In the third experiment, just-noticeable forward and backward displacements of the middle sound marker were measured by a transformed updown method. The prediction that the interval of uncertainty was closer to the initial than to the final sound marker was confirmed. The three experiments demonstrated the existence of unilateral temporal assimilation, and it is argued that this perceptual mechanism causes a category of 1:1 rhythms, despite a considerable change in temporal ratio between two contiguous time intervals.

When a relatively short empty time interval is preceded by an even shorter one, its duration can be underestimated remarkably. This phenomenon, called time-shrinking, has been investigated with patterns consisting of two time intervals. In five experiments, we investigated whether underestimation of the last interval would occur when it was preceded by two time intervals. Significant underestimations of the last interval occurred in some of those patterns. The influence of the second preceding interval was dominant, but in some patterns, the first preceding interval could shrink the subjective duration of the last time interval directly. The first interval could also affect perception of the duration of the last one indirectly by shrinking the second interval, as a result of which the latter either shrank the last interval more strongly or became too short to shrink it. There were two types of temporal patterns in which the perceived duration of the last interval could not be explained by time-shrinking or its propagation through the pattern. It seemed plausible that auditory Gestalt principles invoked strong figural organizations in these patterns, which rendered the time-shrinking mechanism inoperative.