Attentional control of texture orientation judgments.

Recent models of texture processing use low level, spatially parallel computations to extract texture properties. The rapid, preattentive nature of texture segregation suggests that these computations are bottom-up in nature. However, the immunity of texture judgments to top-down influences remains to be tested. Here we investigate the degree to which judgments of texture orientation are susceptible to top-down attentional control. Observers view a brief display composed of variously luminant texture elements (line segments) alternately (in checkerboard arrangement) oriented up/right (at 71.5 degrees ) or up/left (at 108.5 degrees ), and are asked to make various judgments. In a given task, the observer attempts on each trial to judge which oriented population of line segments has an intensity histogram that best matches a given target histogram. Performance demonstrates adaptive flexibility across different tasks, suggesting that observers are able to exercise significant top-down control over texture orientation computations. Specifically, observers can attend selectively to positive contrast texture elements, to negative contrast texture elements, or to high (positive and negative) contrast texture elements. More generally, observers perform well if the target histogram can be approximated by a weighted average of positive and negative half-wave rectifiers. Performance is poor for histograms that cannot be captured in this way. These results suggest that attentional control in these tasks is limited to adjusting the relative gain of the on- and off-center systems.