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Depth release of illusory contour shape in the Ehrenstein grid
T Watanabe1, J E Nanez, M A Moreno
1Vision Science Laboratory, Arizona State University West, Phoenix 85287-5906, USA.
Vision Research
|October 1, 1995
Summary
Illusory shapes in the Ehrenstein grid lose shape constancy when viewed from an angle, deforming significantly. This "depth release" is less pronounced with real contours, suggesting weak depth signals from illusory contours.
Area of Science:
- Visual Perception
- Illusory Contours
- Shape Constancy
Background:
- The Ehrenstein grid generates illusory patches with illusory contours.
- Shape constancy is the perception of an object's shape as stable despite changes in its retinal image.
- Previous research explored 'depth capture,' where depth cues influence illusory shape perception.
Purpose of the Study:
- To investigate whether illusory patches in the Ehrenstein grid exhibit shape constancy.
- To determine how viewing angle affects the perceived shape of illusory contours.
- To compare the shape constancy of illusory contours versus real contours.
Main Methods:
- Observers viewed the Ehrenstein grid directly and at various angles of slant.
- Participants matched the apparent shape of the illusory patches to reference stimuli (circle or ellipse).
- The experiment was repeated using real contours instead of illusory contours.
Main Results:
- When viewed at a slant, the illusory patches deformed into an oval shape, indicating a loss of shape constancy.
- This deformation was significantly reduced when real contours replaced illusory contours.
- The dissociation of shape perception from depth cues was termed 'depth release'.
Conclusions:
- Illusory contours in the Ehrenstein grid demonstrate limited shape constancy.
- Depth cues appear to have a weaker influence on illusory contours compared to real contours, leading to 'depth release'.
- This suggests that illusory contours provide weak or ineffective depth signals.
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