On the robustness of time-shrinking

Time-shrinking is a well-established perceptual phenomenon by now. When two empty time intervals, marked by short sounds, are presented contiguously, the first interval can shrink the second one perceptually. This is almost always the case when the first interval is shorter than the second one, unless the difference gets greater than approximately 80 ms. The phenomenon is rather compelling, so it can be called an illusion of time perception. Our purpose in the present study is to show by three experiments how robust this illusion is. The first experiment showed that time-shrinking operates also when the last time interval is preceded by more than one interval (up to five at least). Moreover, the number of preceding intervals had no effect upon the amount of shrinking. The second and third experiment studied the effect of sound marker frequency on time-shrinking. It was found that the illusory phenomenon clearly appeared even when the sound marker frequencies differed by more than two octaves. However, the amount of shrinking appeared to be largest when frequencies were equal.