Reduction of temporal uncertainty facilitates stimulus-driven processes in spatial selection

Previous studies have shown that the reduction of temporal uncertainty facilitates target selection in visual search. We investigated whether this beneficial effect is caused by an effect on stimulus-driven processes or on goal-driven processes in spatial selection. To discriminate between these processes, we employed a visual search task in which participants searched for a shape target while ignoring a color singleton distractor. As an index of stimulus-driven processes, we measured the N2pc evoked by the singleton distractor (N-D). As indices of goal-driven processes, we measured the N2pc evoked by the target (N-T) and the distractor positivity (P-D) evoked by the singleton distractor, respectively. We observed that reducing temporal uncertainty modulated the amplitude of N-D and the onset latency of the N-T, but did not modulate the amplitude of the P-D. These results are consistent with the view that a reduction of temporal uncertainty influences non-selective, stimulus-driven processes in spatial selection.