In a previous study, we presented psychophysical evidence that time-shrinking (TS), an illusion of time perception that empty durations preceded by shorter ones are underestimated, gives rise to categorical perception on the temporal dimension (Sasaki, Nakajima, and ten Hoopen,1998). In the present study, we first surveyed studies of categorical rhythm perception, and then described four experiments we did to further the evidence that TS causes categorical perception on the temporal dimension. In the first experiment, participants judged the similarity between pairs of /t1/t2/ patterns (slashes denote short sound markers delimiting the empty time intervals t1 and t2).

A cluster analysis and a scaling analysis showed that patterns liable to TS piled up in a 1:1 category. The second and third experiments were improved replications in which the sum of t1 and t2 in the /t1/t2/ patterns was kept constant at 320 ms. The results showed that the 12 patterns /115/205/, /120/200/, …, /165/155/, /170/150/ formed a 1:1 category. The fourth experiment utilized a direct scaling procedure to establish the subjective temporal ratio of the /t1/t2/ patterns and a 1:1 category was established containing the 11 patterns /120/200/, /125/195/, …, /165/155/, /170/150/. On basis of these results we estimated a domain of perceived 1:1 ratios as a function of total pattern duration (t1 + t2) between 160 and 480 ms. We discussed the implications of this study for rhythm perception and production.