Effects of Exposure Duration, Cue Reduction, and Temporary Monocularity on Size Matching at Short Distances*

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Abstract
The effects of exposure duration, accommodation and convergence, and temporary monocularity on size matching at short distances and the interaction among these variables were studied. Test objects, subtending a constant visual angle, were presented at six distances ranging from 30 to 270 cm. Four groups, of 30 subjects each, made size matches with unrestricted vision and through a reduction screen, under continuous and short-duration (10 μsec) illumination, binocularly and monocularly. The results implied that accommodation and convergence begin to make a significant contribution to matched size only at distances less than about one meter. When vision of the entire visual field was unrestricted, short-duration exposure had no effect on size matches. When a reduction screen was used, short-duration exposure had no effect on size matching from 120 to 270 cm, but increased matched size at closer distances. In all conditions of the experiment, matches made with binocular vision were identical with those made with monocular vision. Size matching for unfamiliar objects is seen to be mediated primarily by monocular cues between one and three meters, and by either monocular cues or oculomotor adjustments at distances of one meter and less.

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