Asynchronous processing of luminance difference and motion in visual perception

Abstract

This study is related with the perception of first-order motion. The processing of visual information in the human brain is accomplished by numerous visual streams. Each stream is specialized to process different attributes of the visual scene. It was already demonstrated that times-to-consciousness of form, color, luminance and motion differ. In the present study, it was investigated whether luminance difference and motion are perceived synchronously. The hypothesis was tested by modifying a particular task in the literature. The stimuli were filled squares presented on a mid-gray background. The luminance of the stimulus was continuously incremented or decremented and the subjects performed a lightness matching task based on the perceived luminance at motion instant. It was hypothesized that if the subjects perceived motion first, they would report luminance values back in time from the instant the motion had occurred. When the luminance-change direction was from dim to bright, the matching errors decreased as a function of luminance at motion instant. When the luminance-change direction was from bright to dim, the matching errors increased as the luminance at motion instant increased. In both cases the reported luminance values at motion instant were biased towards the luminance-change direction. This suggested that motion was perceived later than luminance difference. A computational model was used to predict the results of the current experiment. However, experimental results were not consistent with either the model prediction or the experimental results reported in the literature.|Keywords: luminance-motion asynchrony, luminance judgment, modular perception, visual memory, computational model