Time dilates more with apparent than with physical speed.

The perceived duration of a moving stimulus correlates positively with its speed. It is not known whether such duration dilation depends on the physical or apparent speed. Here we show the latter to be true. The perceived duration of a shortly presented (500, 900, 1300 ms) Gabor patch whose carrier moved at 1°/s in a direction opposite to a background of random black dots rigidly moving at 3°/s appeared to last 20% longer and to drift 240% faster than the same Gabor carrier moving in the same direction as the random-dot background. Assessment of the perceived speed of each of the two configurations relative to a moving Gabor patch in the absence of the moving background allowed the comparison of the observed duration dilation with that obtained as a function of the corresponding physical speeds, which should have yielded a dilation of only 7%, i.e., three times less. In line with the proposal that perceived duration correlates with the strength of the neural response evoked by the stimuli to be timed, the present data can be accounted for by the increased responsiveness of antagonistic center-surround motion-receptive fields when stimulated with center-surround antagonist motions.