Figure 5.

Visual search with simultaneously presented targets and probes. On each trial, subjects were presented with a search array consisting of a grid of green distractor letters and either a single letter of the target color (target-only trial), a single letter of the nontarget color (probe-only trial), or one letter of each color, as shown here (target-plus-probe trial). In the example shown, the subject has been instructed to search for blue letters and ignore other colors, making the red letter the probe; 50% of subjects received opposite instructions. Subjects' initial gaze locations at array onset were controlled by presentation of a dynamic fixation cross, which initially filled the display and then rapidly zoomed in to a randomly selected grid location.