The deployment of visual spatial attention during visual search predicts response time: electrophysiological evidence from the N2pc

We tracked the deployment of visual spatial attention as indexed by an electrophysiological event-related potential named the N-2-posterior-contralateral (N2pc). We expected that a stronger and/or earlier deployment of attention would predict faster responses in a visual search task. We tested this hypothesis by sorting the electrophysiological segments into two categories (slow vs. fast) by trial-by-trial response times (RTs), for each participant, on the basis of the median RT within each condition of the experiment. We also classified participants on the basis of overall mean RTs into those faster than the group median and those slower than the group median. The N2pc was larger and earlier for fast responders compared with slow responders. Furthermore, within each of these groups, faster responses were associated with a larger and earlier N2pc. These results provide further evidence that the N2pc is a valid index of the deployment of visual attention, and suggest that a more effective deployment of visual spatial attention (larger and/or earlier N2pc) predicts a faster response, both within and between subjects.