Reaching for virtual objects: binocular disparity, retinal motion and the control of prehension

Bradshaw, Mark F.; Hibbard, Paul B.

doi:10.1590/s0004-27492003000600007

Cited by 2 publications

(1 citation statement)

References 38 publications

(53 reference statements)

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“…However, the fact that we find performance to be affected by an illusion in the processing of binocular disparity is interesting, given its important role in the visual control of prehension. Consistent with these results, we have also established that prehension is subject to similar biases in the recovery of shape and distance from binocular information as are well known in the perceptual domain (Johnston 1991;Bradshaw and Hibbard 2003;Hibbard and Bradshaw 2003).…”

Section: Discussionsupporting

confidence: 88%

2-D Tilt and 3-D Slant Illusions in Perception and Action Tasks

Hibbard

Bradshaw

2006

Perception

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There is now a well established dissociation between perception and action based primarily on neuropsychological evidence [Milner and Goodale, 1995 The Visual Brain in Action (Oxford: Oxford University Press)]. Although equivocal, an important source of evidence from normal observers is that ‘perceptual illusions’ may affect the systems differently. We investigated the relative effects of 2-D tilt and 3-D slant illusions in the two domains, using similar tasks to those employed originally by Milner and Goodale. Subjects were required to either post a card through, or set a paddle to match the orientation of, a plane that was presented in two conditions: surrounded by a striped surface tilted between +90° and −90° (2-D tilt contrast), or surrounded by a disparity defined surface slanted in depth between +60° and −60° (3-D depth contrast). For 2-D tilt, action and perception were equally affected by the illusion, whereas in the 3-D condition they were not. Here, the illusion appeared greater in the posting than in the perceptual task. We conclude that, although no qualitative differences exist, there were quantitative differences between perception and action tasks in the binocular condition.

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Section: Discussionsupporting

confidence: 88%

2-D Tilt and 3-D Slant Illusions in Perception and Action Tasks

Hibbard

Bradshaw

2006

Perception

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Two eyes in action

Brenner

Smeets

2005

Exp Brain Res

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Do relative binocular disparities guide our movements in depth? In order to find out we asked subjects to move a 'cursor' to a target within a simulated horizontal plane at eye height. They did so by moving a computer mouse. We determined how quickly subjects responded to the target jumping in depth. We found that it took subjects about 200 ms to respond to changes in binocular disparity. Subjects responded just as quickly if the cursor was temporarily only visible to one eye near the time that the target jumped in depth, and less vigorously, though just as quickly, if the cursor jumped rather than the target, so the fastest binocular responses cannot be based directly on the relative retinal disparity between the target and the cursor. Subjects reacted faster to changes in the target's height in the visual field than to changes in binocular disparity, but did not react faster to changes in image size. These results suggest that binocular vision mainly improves people's everyday movements by giving them a better sense of the distances of relevant objects, rather than by relative retinal disparities being used to directly guide the movement. We propose that relative disparities only guide parts of very slow movements that require extreme precision.

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Reaching for virtual objects: binocular disparity, retinal motion and the control of prehension

Cited by 2 publications

References 38 publications

2-D Tilt and 3-D Slant Illusions in Perception and Action Tasks

2-D Tilt and 3-D Slant Illusions in Perception and Action Tasks

Two eyes in action

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