9306776 Blakeslee The majority of experiments on visual perception have been concerned with visual thresholds, that is, with measuring the weakest stimulus, for example the intesity of a spot of light, which is just barely visible to human observers. Most of what is called "seeing", however, corresponds to the neural processing of stimuli which are very much stronger than threshold. Such stimuli are referred to as suprathreshold. If a comprehensive scientific understanding of visual perception is to be achieved, then the study of the response of the visual system to these suprathreshold stimuli is essential. Of the many types of perceptual experiences which might be studied (e.g., those of stimulus motion, stereoscopic depth, texture, etc.), the goal of the research planning grant for women is to increase understanding of suprathreshold brightness, contrast and color perception. Whereas the threshold for a stimulus is relatively unaffected by surrounding stimuli, most visual illusions are based upon the fact that suprathreshold perception is strongly influenced by the surrounding visual context. The specific purpose of the proposed experiments is to investigate how the perception of stimulus brightness, contrast and color depends upon surrounding stimuli (i.e., the size and/or shape, luminance and/or contrast, and color of the surround). ***
