Scaling spatial extent, velocity and duration of motion.

Experiments on magnitude estimation of spatial extent, velocity and duration of 11 moving stimuli which had low correlations between the stimulus attributes revealed psychophysical curves of different slopes and shapes for the three attributes of motion. A psychophysical power function with an exponent almost equal to 1.0 described the magnitude estimation of distance. Deviations in velocity judgments were observed with shortening the spatial extent of motion. Duration estimation determined by moving stimuli was found to differ significantly from the estimation of time intervals of the same range presented with stationary light stimuli (Marinova, Mitrani, Yakimoff, 1980). The results indicate that velocity cannot be regarded as a directly perceived attribute of motion. Distance only seems to be directly perceived.