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Measuring Sensitivity to Viewpoint Change with and without Stereoscopic Cues
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Projective invariance and picture perception
1Defence and Civil Institute of Environmental Medicine, Human Factors Division, North York, Ontario, Canada.
Perception
|January 1, 1990
Summary
Visual perception may not rely on projective geometry for shape constancy. Experiments suggest observers lack direct access to projective shape equivalence, challenging the projective thesis.
Area of Science:
- Cognitive Psychology
- Visual Perception
- Geometry
Background:
- Shape constancy is crucial for visual perception.
- The projective thesis posits that shape constancy relies on perceiving projective equivalence.
- This study investigates the validity of the projective thesis.
Purpose of the Study:
- To empirically test the projective thesis of shape constancy.
- To determine if observers have direct access to projective shape equivalence.
- To assess the role of projective geometry in visual shape perception.
Main Methods:
- Four experiments involved matching and reproducing abstract planar shapes.
- Stimuli underwent rotation in the picture plane and pictured rotation in depth.
- Planar analogue of cross ratio measured departure from projective equivalence.
Main Results:
- Perception of projective equivalence was not uniform.
- Non-uniformity occurred where Euclidean equivalence was also not judged uniformly.
- Findings held for both recognition and production tasks.
Conclusions:
- Confidence in the projective thesis is undermined by general testing.
- Direct access to projective equivalence in visual perception is questionable.
- The projective thesis may not fully explain shape constancy.
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