Blinks and other ocular artifacts were corrected using the method of Gratton, Coles, and Donchin (1983). Trials consisted of 2 s of data, including a 500 ms prestimulus baseline. Trials with activity >100 μV were excluded from further processing. Averaged ERPs to targets were constructed separately according to the number of standards preceding the target: 1, 2, 3, or 4. P3 amplitude was defined as the point between 280 and 600 ms at which amplitude of the average waveform was maximal. Current analyses were performed on ERPs only from the Pz electrode and averaged over easy/hard target conditions.
