Sikl R, Simecek M, 2003, "Size constancy in near and far visual space" Perception 32 ECVP Abstract Supplement
Size constancy in near and far visual space
R Sikl, M Simecek
Binocular perceptual cues are commonly thought to be among the most important optical sources of information necessary to achieve size constancy. What happens when we observe objects in the distance where the efficiency of these cues sharply drops? In order to test size constancy for different distances (2 - 10 m), we conducted a relative-size-judgment experiment where two stimuli were presented to an observer at the same viewing distance, but in mutually different orientations. Observers binocularly viewed a stimulus defined by four red LEDs lying on the ground surface, and their task was to match the lengths of two opposite intervals. Both intervals were crossed in the middle of their length; therefore, in the case of a correct answer, the four dots formed a rectangle. We have found that the influence of orientation is not constant across all viewing distances studied. Whereas judgments of the observers were independent of relative orientations at the distance of 2 m, the latter became a critical factor as the distance of the stimuli was increased. The accuracy and reliability of judgments at greater distances linearly decreased with increasing difference between orientations, indicating the determining role of retinal size information.
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