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Nonveridical visual direction produced by monocular viewing.

1981; American Psychological Association; Volume: 7; Issue: 5 Linguagem: Inglês

10.1037/0096-1523.7.5.937

1939-1277

Hiroshi Ono, Elke U. Weber,

Ophthalmology and Visual Impairment Studies

We examined the nonveridicality of visual direction produced by monocularviewing. In Experiment 1,19 subjects pointed to a small light and moved a smalllight to their subjective median plane. The extent of constant error under mon-ocular and binocular viewing conditions differed in both tasks (p < .001). Themonocular-binocular difference was larger when the viewing distance was 25 cmthan when it was 50 cm (p < .01). Also, correlations between phoria and mon-ocular-binocular differences ranged from .58 to .77, depending on viewing dis-tances and tasks. The effects of phoria within the context of Hering's principleof visual direction can account for these results. In Experiment 2, the samesubjects adapted to phoria-induced error by placing a finger over a monocularlyviewed target. The difference in their pointing responses before and after thetask were reliable (p < .005), and the correlations between phoria and the pre-to posttest differences were .45 or .77, depending on the number of adaptationtrials. We argue that all monocular experiments dealing with visual directionshould control for these effects.