Figure embeddedness as a function of the orientation embedding-field contours.

The 'oblique effect' was studied with the use of an embedded-figures task in which the percentage of contextual or embedding contours aligned in the same orientations as those comprising the hidden forms was systematically varied. For hidden forms comprised either of horizontal and vertical contours, or of oblique (45 degree and 135 degree) contours, search times increased markedly as the percentage of aligned contextual contours increased. Although the rate at which embeddedness increased was the same for both orientations, search times were consistently greater for locating obliquely oriented targets (p less than 0.05), and search time variance was significantly greater (p less than 0.025) on trials in which the hidden form was oblique. The results suggest that the laws of organization governing embeddedness apply equally to oblique and horizontal-vertical orientations, but perceptual processing of oblique orientations is poorer. The relationship between search time and aligned contour is discussed in terms of the dual processes of extraction and synthesis in visual search.