Local orientation cues and their interactions

Perception of second- and third-order orientation signals, and their interactions

Jonathan D. Victor, Daniel J. Thengone, and Mary M. Conte

Journal of Vision 13, 1-21 (2013)

Abstract

Orientation signals, which are crucial to many aspects of visual function, are more complex and varied in the natural world than in the stimuli typically used for laboratory investigation. Gratings and lines have a single orientation, but in natural stimuli, local features have multiple orientations, and multiple orientations can occur even at the same location. Moreover, orientation cues can arise not only from pairwise spatial correlations, but from higher-order ones as well.

To investigate these orientation cues and how they interact, we examined segmentation performance for visual textures in which the strengths of different kinds of orientation cues were varied independently, while controlling potential confounds such as differences in luminance statistics. Second-order cues (the kind present in gratings) at different orientations are largely processed independently: there is no cancellation of positive and negative signals at orientations that differ by 45 deg. Third-order orientation cues are readily detected, and interact only minimally with second-order cues. However, they combine across orientations in a different way: positive and negative signals largely cancel if the orientations differ by 90 deg. Two additional elements are superimposed on this picture. First, corners play a special role. When second-order orientation cues combine to produce corners, they provide a stronger signal for texture segregation than can be accounted for by their individual effects. Second, while the object vs. background distinction does not influence processing of second-order orientation cues, the processing of thirdorder orientation cues are influenced by this distinction.


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