Independent texture and luminance processes in globally pooled shape K W S Tan, E Dickinson, D Badcock |
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School of Psychology, University of Western Australia, Australia
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| Shapes can be defined by paths of luminance contrast or by boundaries of texture contrast. Global pooling of local information around an explicitly-defined luminance contour has been shown to occur but this has not been demonstrated for texture segmentation defined shapes. Research has also suggested texture and luminance cues-to-shape are integrated by the visual system for detection of the presence of a shape; it was of interest if this extended to shape discrimination. Shapes deformed from circular by a sinusoidal modulation of radius defined either by a luminance-border, texture-border or both these cues were used in a two-interval force choice task. As number of cycles of modulation increased, discrimination thresholds fell rapidly indicative of global pooling for all stimuli. Also, thresholds for shapes defined by both cues matched predictions based on an independent-cue vector sum of individual thresholds. We surmise that local elements around a contour are processed globally by a shape-detection mechanism but integration was not combined across shape-cues. This suggests the existence of separate mechanisms for luminance-defined and texture-defined contours. |
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