The Interaction Between the Edge Effect and Target Conspicuity in Visual Search

Abstract

The term "edge effect" in visual search is used to describe the finding that targets appearing in the outer half of a display have longer search times than those appearing in the inner half. The interaction between the edge effect and target conspicuity was explored using two experiments. Under conditions of target uncertainty, it was shown that the magnitude of the edge effect was unaffected by target conspicuity. In addition, two manipulations of the edge effect indicated that as the edge effect decreased, the difference between the search times of inconspicuous and conspicuous targets increased. The results are explained in terms of a model based upon the size of the "mesh" of fixations used to cover the display. Two computer simulations confirmed that the size of this mesh and the magnitude of the edge effect are inextricably related.