Second-order orientation cues to the axis of motion.

Geisler's [Geisler, W. S. (1999). Motion streaks provide a spatial code for motion direction. Nature, 400, 65-69] model of motion processing proposes that image smear arising from extended integration periods in Simple cells creates motion streaks which indicate the axis of motion. Orientation cues were provided using textured dot-pairs composed of randomly-placed luminance increments and decrements giving contours with the same average luminance as the background and incompatible with smear. These contours were equally effective in signalling both motion axis and coherence. The results support the assertion that extended contours can determine the perceived axis of motion and that the motion system can use second-order texture cues for this purpose. Inputs of this type are therefore required for both Geisler's (1999) and Barlow and Olshausen's [Barlow, H. B., & Olshausen, B. A. (2004). Convergent evidence for the visual analysis of optic flow through anisotropic attenuation of high spatial frequencies. Journal of Vision, 4, 415-426] models of this ability.