Figure 1.

Schematic of the visual search task used in all experiments. Each trial began with a noise mask followed by either an unrelated preview (a white square) or an informative preview (target or distracter) for 1 s. This was followed by a search array containing one oddball. Subjects had to indicate, using a key press, whether the target was on the left or right of the screen. In the actual experiment, stimuli were shown on a black background in a 6 × 6 search array.