Electroencephalographic (EEG) and electrooculographic (EOG) data were filtered and amplified with a Grass Model 12c Neurodata Acquisition System (Grass Instruments, Quincy, MA). Signals were collected through AC amplifiers with 1/2 amplitude low-and high-frequency filter settings at .01 and 30 Hz (18 dB/octave roll-off), respectively. EEG signals were recorded from the Pz, P3, and P4 scalp sites using an electrode cap with a linked ears reference. A ground electrode was affixed to the right shin, and EOG sensors were placed above and to the temporal side of an eye. Electrode site impedance was kept below 5 kΩ for the scalp sites and the ears and below 10 kΩ for the ground and EOG sites. Data were sampled during a 2,000-ms epoch with a 500-ms prestimulus baseline at a rate of 256 Hz. If a participant failed to respond within the epoch or if the A–D converter became saturated, the trial was rejected and repeated after the presentation of two additional neutral stimuli. This was done to preserve the global probability of target versus neutral stimuli while ensuring that participants had the same number of trials contributing to the event-related potentials.
