Fig. 1.

Sample stimulus display with a an irrelevant distractor present and b no distractor. Participants were instructed to work through the matrix from left to right, starting at the top, and to indicate whether each character was a letter (pressing the “0” key) or a digit (pressing the “2” key). The distractor was presented immediately following one of the target responses. If, for example, the distractor was presented following the response to the third item (“1”) in the matrix shown, then lag 0 refers to RT to the next item (“6”), lag 1 to RT to item “F,” and so forth