The Purves Laboratory is continuing to study visual perception and its neurobiological underpinnings. Ongoing investigations include understanding the perception of brightness, color, orientation, motion, and depth. The unifying theme of these several projects is the hypothesis that visual percepts are generated according to a wholly empirical strategy. The strategy represents in perception the empirical significance of the stimulus rather than its properties. This theory of vision and its relation to cortical structure and function is being explored by examining in probabilistic terms the perceptual responses of human subjects, the properties of virtual organisms that evolve in defined visual environments, and the response properties of visual cortical neurons in experimental animals. Current work is focused on the validation of the theory using natural image databases with complete information about luminance, color and range (physical geometry), asking whether the corresponding perceptual phenomenology is accurately predicted by the statistical information in these proxies of human experience. This empirical theory of vision is also being extended to understanding the phenomenology of music, and to audition more generally.