Texture segregation and orientation gradient.

Rapid texture segregation is examined using filtered noise textures. The stimuli consist of a foreground region of filtered noise with one dominant texture orientation against a background region with a different dominant orientation. Shape discrimination of the foreground region is measured as a function of the difference in orientation between the two regions (delta theta), the distance over which the dominant orientation rotates from the background to the foreground value (delta chi), and the dominant spatial frequency of the textures (f). Performance declines with smaller delta theta, larger delta chi, and lower f. These effects are partially independent of viewing distance, which implies that it is the relative or object spatial frequency, not retinal spatial frequency, which determines performance in this task. We present a model consisting of channels tuned for orientation and spatial frequency which compute local oriented energy, followed by (texture) edge detection and a cross-correlator which performs the shape discrimination. Monte Carlo simulations of this model are in accord with the degradation in performance with increased delta chi and decreased delta theta.