Salience detection and attentional capture.

There is an ongoing debate to what extent irrelevant salient information attracts an observer's attention and is processed without the observer intending to do so. The present experiment investigated attentional capture of salient but irrelevant objects and compared target processing in target-and-distractor to target-only trials. Both form and color singletons were used and their target-distractor assignment was interchanged. Thus the general impact of the presence of a salient distractor on target processing could be separated from the impact of the specific target-distractor salience relation. Response latencies and event-related brain potentials (ERPs) were registered. Results showed a strong influence of the mere presence of an irrelevant distractor on target processing: both the visual N1 and the posterior N2 showed better attention focusing in target-only trials compared to target-and-distractor trials. Response times and N2pc results, on the other hand, showed evidence in favor of salience-specific attention allocation. N2pc results indicated that the distractor affected the allocation of attention in trials with form targets and color distractors but not in the opposite condition. Taken together, results showed a general impact of irrelevant salient singletons on search behavior when they were presented simultaneously with relevant singletons. The allocation of focal attention (as mirrored by the N2pc), however, was also influenced by the specific target-distractor salience relation.