Abstract

Motion of very small amplitudes (5 sec or less) can be detected when the frequency of motion is optimal (2–4 Hz).¹ Previous research has shown that in some conditions, relative motion can be discriminated whenever motion can be detected at all.² In this experiment, we determined the range of frequencies over which this relationship holds. We used two sinusoidally oscillating dots to determine the temporal frequency response function of relative motion discrimination. The subject was presented with two dots that either oscillated inphase (the dots moved in the same direction) or in counterphase (the dots moved in opposite directions). The subject was required to discriminate between the two types of motion for a range of temporal frequencies. When the temporal frequency of the presented stimuli is optimal (~4 Hz), the visual system is remarkably adept at discrimination relative motion. However, a temporal frequency of as low as 8 Hz degrades thresholds and 12 Hz increases them by a factor of 5.33 ± 1.33.

© 1991 Optical Society of America