Spatio-temporal interaction and brightness judgments in sequentially presented,partially overlapping rectangles

Ss made magnitude estimates of brightness to three areas within a display consisting of two sequentially presented partially overlapping rectangles of light. The three areas were the singly stimulated region of the rectangle presented first (the trailing flank), the doubly stimulated overlap region, and the singly stimulated region of the rectangle presented second (the leading flank). The stimuli were presented in right-left or left-right order with stimulus onset asynchronies (SOAs) of 0, 25, 50, 75, 100, and 125 msec. A further condition was flank width. The results indicated that the apparent brightness of the overlap region decreased with increasing SOA. The leading flank was judged to increase in apparent brightness, while the trailing flank remained constant.