Attention-based texture segregation

Luminance- or color-defined +/-45 degrees-oriented bars were arranged to yi eld single-feature or double-conjunction texture pairs. In the former, the global edge between two regions is formed by differences in one attribute ( orientation, or color, or luminance). In the color/orientation double-conju nction pair, one region has +45 degrees red and -45 degrees green textels, the other -45 degrees red and +45 degrees green textels (the luminance/orie ntation double-conjunction pair is similar); such a pair contains a single- feature orientation edge in the subset of red (or green) textels, and a col or edge in the subset of +45 degrees (or -45 degrees) textels. We studied w hether edge detection improved when observers were instructed to attend to such subsets. Two groups of observers participated: in the test group, the stimulus construction was explained to observers, and they were cued to att end to one subset. The control group ran through the same total number of s essions without explanations/cues. The effect of cuing was weak but statist ically significant. Feature cuing was more effective for color/orientation than for luminance/orientation conjunctions. Within each stimulus category, performance was nearly the same no matter which subset was attended to. On average, a global performance improvement occurred over time even without cuing, but some observers did not improve with either cuing or practice. We discuss these results in the context of one versus two-stage segregation t heories, as well as by reference to signal enhancement versus noise suppres sion. We conclude that texture segregation can be improved by attentional s trategies aimed to isolate specific stimulus features.