An Introduction to the Special Issue on “Dealing with Distractors in Visual Search”

Visual search is an imperative human skill. Whether we are attempting to find a lost set of keys in our apartment or a can of soup on a grocery store shelf, we are constantly scanning our cluttered visual environments for behaviorally-relevant objects. A key question about visual search is how we guide attention to objects that are related to our immediate goals. Traditional models have been framed in terms of enhancing or prioritizing features of objects that match the features of the search target. For example, if we were searching a countertop of cooking ingredients for celery, we might restrict our attention to only green items. Recent research, however, has highlighted another mechanism that might guide attention: the rejection of distracting non-target objects. That is, visual attention may also be guided away from items that mismatch expected features of the target. For example, while searching for the celery, we might inhibit a salient red can of paprika or the blinking clock display of the oven. Understanding the role of inhibition in attentional guidance is relevant to developing basic-science models of visual search. It is also relevant to applied settings where we attempt to design effective visual warning signals, that we do not want to be ignored.

The current special issue on “Dealing with Distractors in Visual Search” focuses on how the visual system handles search items that are known to be task-irrelevant. More specifically, the current issue includes a variety of studies that explore how individuals might (or might not) suppress irrelevant items during visual search. To explore this topic, the articles in this special issue employ a variety of experimental techniques common to visual cognition, including psychophysics, eye tracking, and event-related potentials (ERPs).

Some of the articles focus on whether physically salient items, such as brightly colored objects or blinking lights, automatically attract visual attention. Historically, many researchers assumed that salient items had an inherent power to involuntarily capture attention, even when observers were looking for a completely unrelated object. But more recent research suggests that observers learn to reject these salient distractors (e.g., Vatterott & Vecera, 2012) and selectively inhibit those salient items in order to prevent attention capture (called the signal suppression hypothesis; for a review, see Gaspelin & Luck, 2018). Many of the articles in the current special issue explore how individuals inhibit of salient items to prevent visual distraction (Burra, Pittet, Barras, & Kerzel, 2019; Chang, Cunningham, & Egeth, 2019; De Tommaso & Turratto, 2019; Gaspelin, Gaspar, & Luck, 2019; Liesefeld, Liesefeld & Müller, 2019; Krasich, Biggs, & Brockmole, 2018; Ruthruff, Kuit, Maxwell, & Gaspelin, 2019; Turatto, Bonetti, Chiandetti, & Pascucci, 2019). Some of these articles use manual response time to assess inhibition, whereas others use eye movements or the distractor positivity (P_D) ERP component.

Other articles focus on inhibition of nonsalient distractors during visual search (Carlisle & Nitka, 2019; Conci, Deichsel, Müller, & Tölner, 2019; Stilwell & Vecera, 2019; Van Moorselaar, Theeuwes, & Olivers, 2019). Namely, there has also been evidence that observers may voluntarily ignore search items during visual search. This may be accomplished by establishing an attentional control setting to suppress certain features (the negative template model; Arita, Carlisle, & Woodman, 2012). A key debate about negative templates is whether they can be used to proactively inhibit search items or whether attention must first shift to the to-be-ignored items before they are suppressed (the search-and-destroy model; Moher & Egeth, 2012). Some of the articles in the current issue explore negative templates and attempt to shed light upon the debate about whether negative templates can proactively guide visual search.

Another theme that (unexpectedly) emerged from the articles in this special issue that the ability to suppress search items may be an automatic consequence on recent experience and implicit learning (De Tommaso & Turatto, 2019; Gaspelin, Gaspar, & Luck, 2019; Hilchey, Weidler, Rajsic, & Pratt, 2019; Pauszek & Gibson, 2019; Stilwell & Vecera, 2019; Turatto et al., 2019; Van Moorselaar, Theeuwes, & Olivers, 2019). This likely highlights an ongoing debate in the field about whether attention is guided by explicit goals (i.e., conscious foreknowledge of the upcoming visual scene) or whether attention is guided by implicit learning processes (e.g., automatic priming from the previous trial). It should be noted that implicit learning has long been proposed to play a crucial role in attentional guidance (e.g., Carlisle, Arita, Pardo, & Woodman, 2011; Cosman & Vecera, 2013; Gaspelin & Luck, 2018a; Geng & Behrmann, 2002; Kristjansson, 2008; Leber, 2009; Maljkovic & Nakayama, 1994, 1996; Vatterott & Vecera, 2012). This topic likely will be an important issue for future research on inhibitory processes on visual attention.

In conclusion, we are very excited for this special issue on “Dealing with Distractors in Visual Search.” We would like to formally thank all of the authors for their excellent contributions to this Special Issue and the reviewers for their time and expertise. We hope that you enjoy the issue and that the current papers inspire future research on the topic.