Figure 2.

On each trial, observers saw four surfaces (one target, three distractors) and reported whether the orientation of the target surface was “horizontal” or “vertical.” In this example, the target is vertical and located in the upper left. Stimuli were presented in the following three conditions. In the simultaneous condition, all four search items are presented at once (a). In the sequential condition, the same search items are presented, but divided into subsets of two across sequential frames (b). In the repeated condition, all four search items are presented across sequential frames in the same configuration (c).