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Abstract: The influence of various angles of convergence on size-distance judgments were investigated by means of interposing polaroids between the eyes of the subject and the stimuli. Convergence changes were controlled by adjusting the distance between two monocularly presented stimuli viewed with crossed vision and uncrossed vision. The results showed that size-distance judgments are conditioned by convergence, the perceptual size and perceptual distance decreases with an increased angle of convergence, and vice versa. Size judgments fall between the law of size constancy and the calculated values predicted by Emmert's law at various converged distances, while distance judgments follow approximately the values of calculated converged distances. The experiments also showed that convergence still serves as a cue for distance at as far as 30 metres, and that distance judgments are so near to the calculated values, from which the conclusion can be made that convergence is primarily a cue for distance perception.From the fact that Perceptual size decreases with increased angles of convergence, it is probable that size constancy, under our experimental conditions, is the result of an associative process of retinal image and convergence, i.e., when an object approaches the observer, the retinal image increases, while at the same time convergence angle also increases, the compensation of which causes a constancy of size.

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