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Eccentricity dependence of the curveball illusion
1Department of Psychology, Concordia University, Montreal, Quebec, Canada. rick.gurnsey@concordia.ca
Summary
The curveball illusion, a visual motion perception anomaly, is weaker with larger stimuli but cannot be equated across the visual field through size scaling alone. This suggests complex changes in visual motion processing.
Area of Science:
- Visual perception
- Neuroscience
- Computational vision
Background:
- The curveball illusion demonstrates a discrepancy between perceived and actual motion direction in peripheral vision.
- This illusion occurs when a Gabor patch moves vertically while its internal grating drifts horizontally.
Purpose of the Study:
- To quantify the curveball illusion's strength across different stimulus sizes and eccentricities.
- To investigate if stimulus size scaling can equalize illusion strength throughout the visual field.
Main Methods:
- Utilized a nulling procedure to measure the perceived motion of Gabor patches.
- Systematically varied stimulus size and visual field eccentricity (distance from the fovea).
Main Results:
- Illusion strength significantly decreases as stimulus size increases.
- Size scaling did not equate the illusion's strength between central (foveal) and peripheral (10° eccentricity) viewing.
Conclusions:
- The curveball illusion is dependent on stimulus size.
- Observed differences in motion processing across the visual field are not solely explained by the scale of underlying neural mechanisms.
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