Visual search asymmetries in three-dimensional space.

Feature-conjunction search performance was investigated as a function of the target's location in three-dimensional (3-D) space. Ten subjects viewed a display that contained 36 shapes, one of which was the target. The targets were presented in one of four quadrants, three depths, and three eccentricities. On a given trial, nontarget distractor shapes were presented at the other 35 locations. The ability to find a target shape was best when it was presented in the upper and right visual fields and was closest to the fixation point in both its depth and eccentricity. These nonuniformities may be partly derived from the link between visual search and an extrapersonal attentional mechanism.