Perceptual illusion and the real-time control of action.

Full Abstract

Participants were cued by an auditory tone to grasp a target object from within a size-contrast display. The peak grip aperture was unaffected by the perceptual size illusion when the target array was visible between the response cue and movement onset (vision trials). The grasp was sensitive to the illusion, however, when the target array was occluded from view when the response was cued (occlusion trials). This was true when the occlusion occurred 2.5 s before the response cue (delay), but also when the occlusion coincided with the response cue (no-delay). Unlike previous experiments, vision and occlusion trials were presented in random sequence. The results suggest that dedicated, real-time visuomotor mechanisms are engaged for the control of action only after the response is cued, and only if the target is visible. These visuomotor mechanisms compute the absolute metrics of the target object and therefore resist size-contrast illusions. In other situations (e.g. prior to the response cue, or if the target is no longer visible), a perceptual representation of the target object can be used for action planning. Unlike the real-time visuomotor mechanisms, perception-based movement planning makes use of relational metrics, and is therefore sensitive to size-contrast illusions.

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Author information

Author/s: Westwood, David A (DA); Goodale, Melvyn A (MA);

Affiliation: Department of Psychology, The University of Western Ontario, London, Ontario, Canada. david.westwood(-atsign-)dal.ca

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Spatial vision (Spat Vis), published in Netherlands. (Language: eng)

Reference: 2003-; vol 16 (issue 3-4) : pp 243-54

Dates: Created 2003/07/15; Completed 2003/09/10; Revised 2006/11/15;

PMID: 12858950, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Cues
Hand Strength - physiology
Humans
Internal-External Control
Memory

Optical Illusions - physiology
Psychomotor Performance - physiology
Reaction Time
Sound
Visual Perception - physiology

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