Abstract
It is known that a directionally ambiguous test stimulus is perceived to move in the same direction as a brief preceding priming stimulus when both stimuli are presented at the same retinal location (visual motion priming). To examine the spatial properties of visual motion priming under different retinal illuminance, we manipulated the distance between the priming and test stimuli. Participants judged the perceived direction of 180 deg phase-shifted, thus directionally ambiguous, sine-wave gratings (test stimulus) displayed immediately after the offset of a smoothly drifting priming stimulus. The distance between priming and test stimuli was varied from 0 to 10 deg in visual angle. Since the spatial summation area broadens under low retinal illuminance, we predicted that visual motion priming would be more conspicuous under mesopic vision than under photopic vision. Contrary to this prediction, as the retinal illuminance decreased and the distance between the primer and the test stimulus increased, the test stimulus was perceived to move in the direction opposite to the priming stimulus. We speculate that different motion integration systems are functioning depending on the retinal illuminance.
