In many sensory dimensions, assimilation of characteristics of perceived events can be found. In the present study, we examined whether assimilation appeared also in time perception, employing time intervals shorter than 300 ms marked by tone bursts. In Experiment 1, we measured points of subjective equality of two neighboring empty time intervals, t1 and t2. The perceived durations approached each other when the difference between t1 and t2 was small. That is, bilateral assimilation took place. In Experiment 2, we measured points of subjective equality of t1 in smaller steps and across a wider durational range than in Experiment 1. We found that t1 was overestimated slightly when it was a bit shorter than t2, and t1 was underestimated slightly when it was a bit longer than t2. The overestimation and the underestimation were considered as typical assimilation. The results also showed that the perception of t1 changed from assimilation to contrast when the difference between t1 and t2 exceeded the range -80 ≤ t1 - t2 ≤ 40 ms.
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