Integration of first- and second-order orientation.
Journal Title: Journal of the Optical Society of America A: Optics, Image Science & Vision - Year 2003, Vol 20, Issue 6
Abstract
The problem of how visual information such as orientation is combined acrossspace bears on key visual abiities, such as texture perception. Orientation signals can be derived fromboth luminance and contrast, but it is not well understood how such information is pooled or how thesedifferent orientation signals interact in the integration process. We measured orientation discriminationthresholds for arrays of equivisible first-order and second-order Gabors. Thresholds were measured asthe orientation variability in the arrays increased, and we estimated the number of samples (or efficiency)and internal noise of the mechanism being used. Observers were able to judge the mean orientation ofarrays of either first- or second-order Gabors. For arrays of first-order and arrays of second-orderGabors, estimates of the number of samples used increased as the number of Gabors increased. When judgingthe orientation of arrays of either order, observers were able to ignore randomly oriented Gabors ofthe opposite order. If observers did not know which Gabor type carried the more useful orientation information,they tended to use the information from first-order Gabors (even when this was poorer information). Observerswere unable to combine information from first- and second-order Gabors, though this would have improvedtheir performance. The visual system appears to have separate integrators for combining local orientationacross space for luminance- and contrast-defined features.
Authors and Affiliations
Harriet A Allen, Robert F Hess, Behzad Mansouri, Steven C Dakin
Keywords
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Integration of first- and second-order orientation.
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