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Localization of shapes: eye movements and perception compared.
Dhanraj Vishwanath1, Eileen Kowler
1Department of Psychology, Rutgers University, 152 Freylinghuysen Road, Piscataway, NJ 08854, USA. dhanraj@john.berkeley.edu
Vision Research
|June 12, 2003
Summary
Object localization relies on a central reference point, often the center of gravity (COG). This study found saccadic and perceptual localization align with the COG, especially in naturalistic sequential scanning tasks.
Area of Science:
- Cognitive psychology
- Neuroscience
- Visual perception
Background:
- Object localization is crucial for visually guided actions.
- The center of gravity (COG) is hypothesized as a default reference point for spatial localization.
- Previous research has not fully explored localization for non-convex shapes with external COGs.
Purpose of the Study:
- To investigate perceptual and saccadic localization of non-convex shapes.
- To determine if the center of gravity (COG) serves as a reference point.
- To compare localization accuracy across different tasks, including sequential scanning.
Main Methods:
- Participants localized non-convex shapes perceptually and via saccades.
- Stimuli included shapes with the COG outside the object boundary.
- Saccade landing positions and fixation loci were recorded during single and sequential scanning tasks.
Main Results:
- Saccades and fixation loci were near the COG, influenced by local features.
- Perceptual localization was near the COG but showed configural effects.
- Sequential saccades accurately localized objects near the COG, unaffected by local features or configuration.
Conclusions:
- Object localization, both perceptual and oculomotor, relies on a computed central reference position, the COG.
- Sequential scanning provides a more accurate measure of the default reference position.
- Spatial pooling, rather than local features, is key for object localization, even when the COG is external.