The power of linear perspective in slant perception and its implication for the neural processing of orientation C Erkelens |
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Helmholtz Institute, Utrecht University, Netherlands
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| Virtual slant is defined here as the slant of a surface based on the assumption of linear perspective. Virtual slants of obliquely viewed 2D figures consisting of skewed columnar grids were computed as a function of depicted slant and slant of the picture surface. Computations were based on an assumption of parallelism. Virtual slants were compared with perceived slants in binocular viewing conditions. Perceived slant was highly correlated with virtual slant. Contributions of screen-related cues, including disparity and vergence, were negligibly small. The results imply that many past findings of both transformation and (apparent) compensation in pictorial viewing are straightforwardly explained by virtual slant. Analysis shows that slant is perceived from converging lines whose angular differences are smaller than the limits that have been measured in orientation discrimination tasks. Slant perception on the basis of linear perspective implies non-local comparisons between line orientations. It suggests a yet unproposed role for the elaborate network of long-range connections between the abundance of orientation detectors in the visual cortex. |
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