An inverse oblique effect in human vision

In the classic oblique effect contrast detection thresholds, orientation di scrimination thresholds, and other psychophysical measures are found to be smallest for vertical or horizontal stimuli and significantly higher for st imuli near the +/- 45 degrees obliques. Here we report a novel inverse obli que effect in which thresholds for detecting translational structure in ran dom dot patterns [Glass, L. (1969). Moire effect from random dots. Nature, 223, 578-580] are lowest for obliquely oriented structure and higher for ei ther horizontal or vertical structure. Area summation experiments provide e vidence that this results from larger pooling areas for oblique orientation s in these patterns. The results can be explained quantitatively by a model for complex cells in which the final filtering stage in a filter-rectify-f ilter sequence is of significantly larger area for oblique orientations. (C ) 2001 Elsevier Science Ltd. All rights reserved.