Stereopsis is the ability of the brain to extract a stereoscopic perceptfrom two correlated retinal images. Stereopsis requires the cooperation of three neural systems: 1) a detection system that signals spatial disparities between correlated interocular features, 2) a control system that uses disparity to control vergence eye movements, and 3) a perceptual system which transforms disparity into signals related to distance and depth. The general view about disparity processing is that stereopsis and eye movements make use of the same networks of disparity detectors. We doubt this view. We believe that disparity detectors subserving stereopsis and vergence have different properties. The belief is based on conceptual considerations as well as the interpretation of a number of experimental results. In this project we propose to test the hypothesis that stereopsis and vergence result from different types of disparity detectors. To examine disparity detection we have developed a novel type of dynamic random-dot stereogram by which we can present well-defined time frames and levels of interocular correlation. We use this method to find stimuli which exclusively induce stereopsis and vergence eye movements. These stimuli will then be presented to subjects in a brain-imaging study in order to find out the cortical areas that are involved in stereopsis and vergence.