Temporal acceleration drives the probability cueing effect in visual search: Evidence for early attentional...

This study used event-related potentials to investigate the neural mechanisms underlying the target-location probability cueing effect, where repeated target appearance at one location improves visual search performance. We aimed to dissociate proactive spatial tuning (attentional enhancement before search array onset) from reactive enhancement (attentional improvement after onset). Behaviorally, targets at the high-probability location yielded significantly shorter reaction times, an effect that scaled with the strength of the spatial bias. Electrophysiologically, our probe-elicited N2pc analysis, intended to measure proactive tuning, yielded inconsistent results and was complicated by an unexpected negative-going baseline shift contralateral to the high-probability location. For reactive mechanisms, the target-elicited N2pc showed a surprising result: its amplitude decreased for targets at the high-probability location, contrary to the expected increase for efficient selection. Crucially, we observed the reliable emergence of an N1pc component at the high-probability location, an earlier marker of attentional selection (125-175 ms) that preceded the typical N2pc (175-255 ms). Latency analysis confirmed that the contralateral negativity onset was significantly earlier for high-probability targets compared to low-probability targets. These findings suggest that the behavioral benefit of target-location probability cueing is driven not by an increase in attentional resources (N2pc amplitude), but by a temporal acceleration of attentional deployment (N1pc presence and earlier latency) to the learned, high-probability location.