Surface segregation driven by orientation-defined junctions.

This study was designed to ascertain whether the human visual system can segregate overlapped surfaces by integrating texture borders at second-order X-junctions. The stimuli used were crossed vertical and horizontal stripes consisting of Gabor micro-patterns. We manipulated the orientation of the center region of each stripe. Observers judged whether the crossed stripes appeared as "two overlapped stripes" or "five individual regions." The results showed that the probability of perceiving overlapped stripes exceeded the chance level (0.5) when the orientation differences between the center and flanking regions were less than 30 degrees. We suggest that the integration of texture borders along each stripe occurs by the filter-rectify-filter mechanism, resulting in the impression of overlapped surfaces. When this fails, the outcome is the perception of five individual regions.