Unique objects attract attention even when faint

Terms of debate: Consensus definitions to guide the scientific discourse on visual distraction

Hypothesis-driven research rests on clearly articulated scientific theories. The building blocks for communicating these theories are scientific terms. Obviously, communication - and thus, scientific progress - is hampered if the meaning of these terms varies idiosyncratically across (sub)fields and even across individual researchers within the same subfield. We have formed an international group of experts representing various theoretical stances with the goal to homogenize the use of the terms that are most relevant to fundamental research on visual distraction in visual search. Our discussions revealed striking heterogeneity and we had to invest much time and effort to increase our mutual understanding of each other's use of central terms, which turned out to be strongly related to our respective theoretical positions. We present the outcomes of these discussions in a glossary and provide some context in several essays. Specifically, we explicate how central terms are used in the distraction literature and consensually sharpen their definitions in order to enable communication across theoretical standpoints. Where applicable, we also explain how the respective constructs can be measured. We believe that this novel type of adversarial collaboration can serve as a model for other fields of psychological research that strive to build a solid groundwork for theorizing and communicating by establishing a common language. For the field of visual distraction, the present paper should facilitate communication across theoretical standpoints and may serve as an introduction and reference text for newcomers.

Learned distractor rejection persists across target search in a different dimension

Attention is guided by several factors, including task-relevant target features, which attract attention, but also statistical regularities associated distractors, which repel attention away from themselves. However, whether feature-based distractor regularities (e.g., color) are extracted automatically from a feature dimension orthogonal to the target-guiding dimension (e.g., shape) remains to be tested. In two experiments, we tested if learned distractor rejection by color operated when color was not part of the attentional control settings, specifically, while attention was guided by a shape-based target template. Participants performed a visual search task for a task-relevant shape in displays containing two unsegregated colors. These displays allowed us to manipulate target guidance (based on shape) independently from distractor-based regularities (based on color). In both experiments we found clear evidence for learned distractor rejection: faster mean response times to locate the target when a consistent distractor color was present than when it was absent. Critically, these task-irrelevant learned distractor rejection effects were robust despite strong target guidance by an orthogonal search dimension. These findings corroborate recent demonstrations of learned distractor rejection during strong target guidance, indicating that learned distractor rejection and target guidance can operate on separate feature dimensions.

Electrophysiological Evidence for the Suppression of Highly Salient Distractors

There has been a longstanding debate as to whether salient stimuli have the power to involuntarily capture attention. As a potential resolution to this debate, the signal suppression hypothesis proposes that salient items generate a bottom-up signal that automatically attracts attention, but that salient items can be suppressed by top-down mechanisms to prevent attentional capture. Despite much support, the signal suppression hypothesis has been challenged on the grounds that many prior studies may have used color singletons with relatively low salience that are too weak to capture attention. The current study addressed this by using previous methods to study suppression but increased the set size to improve the relative salience of the color singletons. To assess whether salient distractors captured attention, electrophysiological markers of attentional allocation (the N2pc component) and suppression (the PD component) were measured. The results provided no evidence of attentional capture, but instead indicated suppression of the highly salient singleton distractors, as indexed by the PD component. This suppression occurred even though a computational model of saliency confirmed that the color singleton was highly salient. Altogether, this supports the signal suppression hypothesis and is inconsistent with stimulus-driven models of attentional capture.

Standing out in a small crowd: The role of display size in attracting attention

Strong evidence supporting the top-down modulation of attention has come from studies in which participants learned to suppress a singleton in a heterogeneous four-item display. These studies have been criticized on the grounds that the displays are so sparse that the singleton is not actually salient. We argue that similar evidence of suppression has been found with substantially larger displays where salience is not in question. Additionally, we examine the results of applying salience models to four-item displays, and find prominent markers of salience at the location of the singleton. We conclude that small heterogeneous displays do not preclude strong salience signals. Beyond that, we reflect on how further basic research on salience may speed resolution of the attentional capture debate.