The proposed project will test the effects of conditions of illumination on the visual latent period, as measured both psychophysically and electrophysiologically, and also on binocular depth-discrimination settings obtained from these same observers. The psychophysical studies on the visual latent period will involve apparent near and far depth-displacement settings in the Pulfrich stereophenomenon, and monocular lateral-displacement settings in the Hess effect and in the Frohlich effect. Research on the Pulfrich effect continues to focus on the development of a very sensitive intra-subject index for the early detection of unilateral pathology in the visual centers or pathways. Comparable latency data will be obtained directly from reaction-time (RT) measures to incremental and decremental light flashes presented against uniformly illuminated backgrounds and also to flashes of increasing luminance presented in the central unilluminated region of annulus surrounds. Correlated electrophysiological latency data on visual evoked cortical potentials (VECP) will also be collected. The RT and VECP data will test a proposed electrical-network theory of neural transmission. The studies on stereoscopic vision will investigate spatio-temporal factors affecting equidistance settings for stationary targets and depth-displacement settings for a transversel oscillating target in the Mach-Dvorak (M-D) effect. The results obtained on the M-D effect will test a proposed spatio-temporal theory of directional localization that may help to elucidate the structure and function of the underlying neural mechanisms. Correlated spatio-temporal experiments on monocular directional localization will be performed on the Hess and Frohlich effects. The total results will serve to specify the optimal testing conditions for this class of spatial responses that may have clinical application in assessing and improving the quality of the binocular fusion mechanism.