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Contrast sensitivity at different positions in the visual field has been measured at various spatial frequencies using a patch of gratin, 0 suitabij tignetted to give a st!mulus localized in both space and spatial frequent\. While contrast sensitivitl along a vertical line through the fixation point f4is ofl' steadily from a maximum at the crntre.(More)
Observers rated the degree of segregation between two textures, each composed of the same two element types but in differing arrangements (a checkerboard arrangement in the middle region of the pattern and a striped arrangement in the top and bottom regions). The two element types in a given pattern were either both solid squares or both center-surround(More)
Models incorporating spatial-frequency- and orientation-selective channels explain many texture-segregation results, particularly when known nonlinearities are included. One such nonlinearity is complex channels. A complex channel consists of two stages of linear filtering separated by a rectification-type nonlinearity. Here we investigate the(More)
Observers were shown patterns composed of two textures in which each texture contained two types of elements. The elements were arranged in a striped pattern in the top and bottom regions and in a checked pattern in the center region. Observers rated the degree to which the three regions were seen as distinct. When the elements were squares or lines,(More)
Complex (non-Fourier, second-order) channels have been proposed to explain aspects of texture-based region segregation and related perceptual tasks. Complex channels contain two stages of linear filtering with an intermediate pointwise nonlinearity. The intermediate nonlinearity is crucial. Without it, a complex channel is equivalent to a single linear(More)
In the probed-sinewave paradigm, threshold for detecting a probe is measured at various phases with respect to a sinusoidally-flickering background. Here we vary the duration of the flickering background before (and after) the test probe is presented. The adaptation is rapid; after approximately 10-30 ms of the flickering background, probe threshold is the(More)
Several recent models of texture segregation have proposed two mechanisms: simple, linear channels (first-order, Fourier mechanisms) and complex channels (second-order, non-Fourier mechanisms). We used the speed-accuracy tradeoff (SAT) method to examine the time course of texture segregation processing in simple and complex channels. The stimuli were(More)