Leonards U, Singer W, 1996, "Texture segregation by orientation differences: colour sensitive but not hue specific?" Perception 25 ECVP Abstract Supplement
Texture segregation by orientation differences: colour sensitive but not hue specific?
U Leonards, W Singer
Segregation of textures on the basis of orientation differences between texture elements is achieved even when these texture elements differ from their surround only by colour (McIlhagga et al, 1990 Vision Research 30 489 -- 495). This finding seems to contradict the assumption that colour and orientation are extracted in separate feature maps (eg Treisman and Sato, 1990 Journal of Experimental Psychology: Human Perception and Performance 16 459 -- 478). To examine whether colour information is evaluated in parallel in different processing streams for the assessment of hue and form, we tested whether texture elements can be segregated if they differ only by specific conjunctions of colour and orientation; texture elements consisted of crosses with their two crossing lines differing in colour. Texture elements defining figure and background had the same coloured composition but the conjunction of colour with the two crossing lines was reversed. Different colour combinations were tested under various luminance contrast conditions, irrespective of the colour combination, segmentation was achieved as long as the two crossing lines of the texture elements differed in luminance. If, however, the different colours of the two crossing lines were approximately equiluminant, segmentation was reduced or impossible. Thus, subjects were able to use for texture segregation conjunctions between luminance and orientation but not between colour and orientation. Our results suggest that colour cannot be associated selectively with differently oriented components of the same texture element. This supports the hypothesis that colour contrast is used in parallel by different processing streams to assess the orientation and hue of contours and reveals limitations in the selectivity with which features are subsequently bound together.