title: Effect of context and efference copy on visual straight ahead.
abstract: Bias in efferent commands to the eye changes the apparent straight ahead direction in an unstructured visual field, but has little effect in a normal visual environment. Naive subjects set a visible marker to appear straight ahead under monocular viewing conditions and while pressing on the viewing eye. Three background conditions were used: a naturalistic landscape photograph, a blank field, and a repeating checkerboard texture that provides strong contours but no information about visual direction. Effect of eyepress on straight-ahead judgments was small but significant with the landscape background, and larger with the blank field; the checkerboard texture yielded a bias halfway between the magnitudes of bias in the other two conditions. A visual capture theory predicts that the textured field should work like a blank one, while an oculomotor theory predicts that it should work like a natural one. Interpreted in this context, the results show the two theories to be about equally important in judging straight ahead. A second experiment with experienced observers and moving backgrounds gave the same result.
authors.affiliation: Program in Experimental Psychology, University of California, Santa Cruz 95064.
authors.forename: B
authors.initials: B
authors.lastname: Bridgeman
authors.forename: J A
authors.initials: JA
authors.lastname: Graziano
mesh_terms: D005133:Eye Movements / Q000502:physiology*; D005403:Fixation, Ocular / Q000502:physiology*; D006801:Humans; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*