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A haptic size-contrast illusion affects size perception but not grasping.
David A Westwood1, Melvyn A Goodale
1School of Health and Human Performance, Dalhousie University, 6230 South Street, Halifax, Nova Scotia, B3H 3J5, Canada. David.Westwood@dal.ca
Experimental Brain Research
|August 5, 2003
Summary
Haptic perception and action show a size-contrast illusion dissociation. Perceived object size is scene-based, while grasping actions use actor-based, absolute size, suggesting a general sensory processing principle.
Area of Science:
- Neuroscience
- Haptic Perception
- Motor Control
Background:
- Object features like size are crucial for perception and action.
- Visual systems show a dissociation between object perception and action control.
- This dissociation may extend to the haptic (touch) sensory system.
Purpose of the Study:
- To investigate if a dissociation exists between haptic perception and haptic-directed action.
- To determine if size-contrast illusions affect haptic perception and grasping movements differently.
Main Methods:
- A haptic size-contrast illusion was employed.
- Participants' perception of target object size was measured.
- The degree of hand opening during grasping movements towards the target object was assessed.
Main Results:
- The haptic size-contrast illusion altered the perceived size of the target object.
- However, the illusion did not affect the hand's aperture during grasping.
- Grasping movements were based on the target object's absolute size, independent of surrounding objects.
Conclusions:
- Haptic perception is scene-based, considering relative object sizes.
- Haptic action control is actor-based, relying on absolute target size.
- Dissociations between perception and action are a general principle across sensory systems.