ABSTRACT
When looking at a visual scene one normally fixates an object and at the same time perceives objects that are closer to or farther from the fixation point. The size of these indirectly seen objects can be perceived veridically only if the visual system processes the following three variables: retinal image size, absolute or fixation distance, and relative distance, i.e., the distance between the point of fixation and any other point lying in front of, or behind it. In the case of binocular vision the relative distances of indirectly seen objects can be determined by processing fixation distance and retinal disparity. An investigation was carried out to determine how perceived distance and perceived size of stereoscopically presented stimuli depend upon fixation distance and retinal disparity. The data revealed that there exists a single functional relation between perceived distance and perceived size which is independent of the fixation distance. This indicates that size scaling in visual perception presumably takes place at the stage of stimulus processing necessary for stereopsis or at a higher level.
