There has been a long-lasting debate about whether salient stimuli, such as uniquely colored objects, have the ability to automatically distract us. To resolve this debate, it has been suggested that salient stimuli do attract attention but that they can be suppressed to prevent distraction. Some research supporting this viewpoint has focused on a newly discovered ERP component called the distractor positivity (P D ), which is thought to measure an inhibitory attentional process. This collaborative review summarizes previous research relying on this component with a specific emphasis on how the P D has been used to understand the ability to ignore distracting stimuli. In particular, we outline how the P D component has been used to gain theoretical insights about how search strategy and learning can influence distraction. We also review alternative accounts of the cognitive processes indexed by the P D component. Ultimately, we conclude that the P D component is a useful tool for understanding inhibitory processes related to distraction and may prove to be useful in other areas of study related to cognitive control.

The human visual system can only process a fraction of the information present in a typical visual scene, and selection is historically framed as the outcome of bottom–up and top–down control processes. In this study, we evaluated how a third factor, an individual's selection history, interacts with top–down control mechanisms during visual search. Participants in our task were assigned to one of two groups in which they developed a history of either shape or color selection in one task, while searching for a shape singleton in a second task. A voluntary task selection procedure allowed participants to choose which task they would perform on each trial, thereby maximizing their top–down preparation. We recorded EEG throughout and extracted lateralized ERP components that index target selection (N T ) and distractor suppression (P D ). Our results showed that selection history continued to guide attention during visual search, even when top–down control mechanisms were maximized with voluntary task selection. For participants with a history of color selection, the N T component elicited by a shape target was attenuated when accompanied by a color distractor, and the distractor itself elicited a larger P D component. In addition, task-switching results revealed that participants in the color group had larger, asymmetric switch costs implying increased competition between task sets. Our results support the notion that selection history is a significant factor in attention guidance, orienting the visual system reflexively to objects that contradict an individual's current goals—even when these goals are intrinsically selected and prepared ahead of time.

Our visual system is constantly confronted with more information than it can process. To deal with the limited capacity, attention allows us to enhance relevant information and suppress irrelevant information. Particularly, the suppression of salient irrelevant stimuli has shown to be important as it prevents attention to be captured and thus attentional resources to be wasted. This study aimed at directly connecting failures to suppress distraction with a neural marker of suppression, the distractor positivity (Pd). We measured participants' EEG signal while they performed a visual search task in which they had to report a digit inside a shape target while ignoring distractors, one of which could be a salient color singleton. Reports of target digits served as a behavioral index of enhancement, and reports of color distractor digits served as a behavioral index of failed suppression, each measured against reports of neutral distractor digits serving as a baseline. Participants reported the target identity more often than any distractor identity. The singleton identity was reported least often, suggesting suppression of the singleton below baseline. Suppression of salient stimuli was absent in the beginning and then increased throughout the experiment. When the singleton identity was reported, the Pd was observed in a later time window, suggesting that behavioral errors were preceded by failed suppression. Our results provide evidence for the signal suppression hypothesis that states salient items have to be actively suppressed to avoid attentional capture. Our results also provide direct evidence that the Pd is reflecting such active suppression.

Visual STM (VSTM) is thought to be related to visual attention in several ways. Attention controls access to VSTM during memory encoding and plays a role in the maintenance of stored information by strengthening memorized content. We investigated the involvement of visual attention in recall from VSTM. In two experiments, we measured electrophysiological markers of attention in a memory search task with varying intervals between VSTM encoding and recall, and so we were able to track recoding of representations in memory. Results confirmed the involvement of attention in VSTM recall. However, the amplitude of the N2pc and N3rs components, which mark orienting of attention and search within VSTM, decreased as a function of delay. Conversely, the amplitude of the P3 and sustained posterior contralateral negativity components increased as a function of delay, effectively the opposite of the N2pc and N3rs modulations. These effects were only observed when verbal memory was not taxed. Thus, the results suggested that gradual recoding from visuospatial orienting of attention into verbal recall mechanisms takes place from short to long retention intervals. Interestingly, recall at longer delays was faster than at short delays, indicating that verbal representation is coupled with faster responses. These results extend the orienting-of-attention hypothesis by including an account of representational recoding during short-term consolidation and its consequences for recall from VSTM.

It is not clear how salient distractors affect visual processing. The debate concerning the issue of whether irrelevant salient items capture spatial attention [e.g., Theeuwes, J., Atchley, P., & Kramer, A. F. On the time course of top–down and bottom–up control of visual attention. In S. Monsell & J. Driver (Eds.), Attention and performance XVIII: Control of cognitive performance (pp. 105–124). Cambridge, MA: MIT Press, 2000] or produce only nonspatial interference in the form of, for example, filtering costs [Folk, Ch. L., & Remington, R. Top–down modulation of preattentive processing: Testing the recovery account of contingent capture. Visual Cognition, 14, 445–465, 2006] has not yet been settled. The present ERP study examined deployment of attention in visual search displays that contained an additional irrelevant singleton. Display-locked N2pc showed that attention was allocated to the target and not to the irrelevant singleton. However, the onset of the N2pc to the target was delayed when the irrelevant singleton was presented in the opposite hemifield relative to the same hemifield. Thus, although attention was successfully focused on the target, the irrelevant singleton produced some interference resulting in a delayed allocation of attention to the target. A subsequent probe discrimination task allowed for locking ERPs to probe onsets and investigating the dynamics of sensory gain control for probes appearing at relevant (target) or irrelevant (singleton distractor) positions. Probe-locked P1 showed sensory gain for probes positioned at the target location but no such effect for irrelevant singletons in the additional singleton condition. Taken together, the present data support the claim that irrelevant singletons do not capture attention. If they produce any interference, it is rather due to nonspatial filtering costs.

Two mechanisms are said to be responsible for guiding focal attention in visual selection: bottom–up, saliency-driven capture and top–down control. These mechanisms were examined with a paradigm that combined a visual search task with postdisplay probe detection. Two SOAs between the search display and probe onsets were introduced to investigate how attention was allocated to particular items at different points in time. The dynamic interplay between bottom–up and top–down mechanisms was investigated with ERP methodology. ERPs locked to the search displays showed that top–down control needed time to develop. N2pc indicated allocation of attention to the target item and not to the irrelevant singleton. ERPs locked to probes revealed modulations in the P1 component reflecting top–down control of focal attention at the long SOA. Early bottom–up effects were observed in the error rates at the short SOA. Taken together, the present results show that the top–down mechanism takes time to guide focal attention to the relevant target item and that it is potent enough to limit bottom–up attentional capture.