EFFECTS OF SIZE AND LUMINANCE OF STIMULUS ON VISUAL STREAM SEGREGATION

To investigate the effects of stimulus size and luminance on visual stream segregation (VISS), I measured the upper limits and the optimal values of the interstimulus interval (ISI) for producing VISS. Although the effect of luminance was small when the stimulus size is large, the results were generally consistent with Korte's second law saying that the ISI decreases as the stimulus intensity increases to produce optimal beta movement. This is favorable to Ohmura's (1982) notion that VISS is functionally equivalent to beta movement because VISS can be regarded as a compound phenomenon consisting of two beta movements. These results show that both of the stimulus size and luminance function as intensity for producing VISS. The process of producing VISS was examined based on Ullman's (1979) theory of motion correspondence.