Configuration influence on crowding.

The influence of configuration on visual crowding was tested. Eight Gabor patches surrounding a central one were arranged in a way that created several global configurations differing by their internal arrangements (smooth contour vs. random), while still preserving pairwise relationships between the target and flankers. Orientation discrimination and contrast detection of the central Gabor were measured. These measurements revealed differences in the magnitude of crowding produced by the different configurations, especially on the discrimination task. The crowding effect was stronger when random configurations were used and was reduced considerably when a smooth one was used. These results showed the typical dependence of crowding on eccentricity and target-flanker separation, which was independent of the configural effect. Controlling flankers' local orientation allowed addressing the nature of the effect. It was found to be sensitive to spatial relations and did not represent a simple averaging of local orientation estimates. Our results show that crowding operates at a level where configuration information has already been extracted. We relate all this to the object-based nature of perception.