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The influence of visual illusions on grasp position
R R Ellis1, J R Flanagan, S J Lederman
1Psychology Department, Queen's University, Kingston, Ontario, Canada. ellisr@psyc.queensu.ca
Experimental Brain Research
|April 16, 1999
Summary
Visual illusions impact object perception but not hand actions. Grasping an object is more accurate than perceiving its size, suggesting vision for action is more precise than vision for perception.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Visual Perception
Background:
- Visual illusions demonstrate a dissociation between vision for perception and vision for action.
- Perceived object size is affected by illusions, but hand aperture during reaching is not.
Purpose of the Study:
- To investigate how visual-position and visual-shape illusions affect the perceived center of an object.
- To determine the impact of these illusions on grasp position for a balanced lift.
Main Methods:
- Two experiments were conducted using visual illusions.
- Participants were asked to estimate object centers and position their grasps for a balanced lift.
Main Results:
- Visual illusions influenced both perceived and grasped estimates of the object's center.
- Grasp position demonstrated greater accuracy (more veridical) compared to perceived position.
Conclusions:
- A partial dissociation exists between visual perception and action, with action being more accurate.
- Findings provide insights into distinct visual processing streams for perception and action.