Some Recent Studies on the Extraretinal Contribution to Distance Perception

Abstract

Some recent studies on the extraretinal contribution to distance perception are reviewed. These experiments demonstrate that vergence can provide reliable information for judgments on the distance of proximal targets in the absence of all other cues. We argue that, although vergence is an unreliable cue at large fixation distances and is subject to a strong contraction bias when studied in isolation, these facts do not imply a minor role for vergence in near-space perception. When additional depth and distance cues are added, the contribution of vergence information becomes more complicated. We present results which indicate that the different cues to depth and distance are combined in a manner that can result in unexpected distortions of visual space. A simple heuristic model which can produce the observed distortions is outlined.