The optimal displacement for the detection of motion.

The optimal spatial displacement for the detection of motion by the human visual system was investigated using spatially narrow band stimuli. Direction discrimination was used for abruptly displaced stimuli. An optimal spatial displacement was found for the detection of motion and this bore a characteristic relationship to the spatial wavelength of the stimuli in motion; it was equivalent to 1/6 of the spatial wavelength of the stimulus for low contrast stimuli and 1/5 of the spatial wavelength for higher contrast stimuli. This finding, which in turn suggests that the spatial subunits of motion detectors may be separated by less than 1/4 spatial wavelength, receives some support from other psychophysical and neurophysiological studies.