Microgenetic analysis of transparency perception

Abstract

In this study the microgenesis of transparency perception was investigated. Two intersecting squares were used as a basic stimulus model. Three surfaces was defined: surface which had the shape of capital Greek letter gamma, surface which had the shape of mirrored L and the little square nested between gamma and L. The gray levels of these surfaces were varied, whereas the background was constantly black. The gray levels variation can produce either transparency, spotlight or mosaic perception. All three categories can be described both locally (three juxtaposed surfaces) and globally (two overlapping squares). The primed matching paradigm and the same-different task were used. The global (squares) and the local (gammas or mirrored Ls) test stimuli were given as same or different pairs. There were the two prime types: identical (equal to test stimuli) and perceptual (related to the transparency, spotlight or mosaic). Prime duration were 50 ms and 400 ms, and the ISI was 30 ms. Ten subjects were asked to respond whether the test stimuli are same or different. The main result indicate that the difference in RT between perceptually primed global and local test stimuli is highly significant in both prime duration conditions and for transparency and spotlight patterns, and is marginally significant for mosaic patterns. The difference was such that the global tests were processed faster than the local tests. These results suggest that complex perceptual descriptions (transparency and the spotlight) are generated very early in the perceptual process (50 ms).