Brightness variation in function of stimulus exposure time

Brightness contrast can be the result of an interaction process with the luminance of the immediate surround (local interactions) or a consequence of perceptual organization (global factors). It is alreadyPosters: Brightness and lightness known that a display with competing local and global factors without exposure time limitations results in a perceived brightness contrast induced by global factors. In this study we used reverse contrast Necker cube type displays with the relative controls. The two experimental stimuli were two medium-gray dashed cubes. The first one, having dark inducer corners, was placed on a light inducer background and the second one, having light inducer corners, was placed on a dark inducer background. The control stimuli were identical to the two experimental displays except that the inducer corners were medium gray. The stimuli were presented for 200, 300, 500 and 1000 ms. We asked observers to match the brightness of the dashed lines of each cube to the brightness of a gray scale. Our results show that the brightness change in function of the exposure time: local factors produced the brightness contrast effect at short stimulus exposure time while at longer exposure time the global factors win the competition and become crucial for brightness perception.