The role of convergence in visual space perception.

Earlier experiments suggest that the perception of relative and absolute distance in binocular space is affected by the convergence angle to the stimulus. The question is how? A hypothesis was proposed in which the obtained effects are accounted for in terms of convergence differences. The hypothesis states that binocular stimuli are related to the rest convergence of the eyes which is assumed to be stable. Two experiments were conducted in which distance estimations were made to single binocular dots. viewed through a polarization stereoscope. The experimental results support the proposed hypothesis. Ever since Berkeley (1709), the roie of convergence in binocular space perception has been much discussed. Experimental results do not support the hypothesis that veridical perception of distances is based on convergence, but neither do they support the opposite hypothesis, i.e. that no relation exists betweenconvergence and perceived distance. The present articleis an attempt to explain the experimental results obtained and to determine the role of convergence in visual space perception. The notation which shah be used is illustrated in Fig. 1. points in the binocular fieeld, egocentric distances of the points from the eyes (D, > D,} in cm, the distance between P. and P,, interpupillary distance, convergence angles of the points in radians, convergence angle of the eyes in the absence of visual stimuli (rest convergence) in radians, horizontal disparity between Pf and P,, the retinal displacement of each dot at rest convergence, perceived egocentric distances of the points in rrn, perceived distance between Pf and P,. If the absolute convergence of the eyes determines perceived distance, then