How Loud Must a Distraction Be? Salience Shapes Second-Order Attentional Suppression

Every moment of waking life, the visual world bombards the brain with far more information than it can possibly process. A busy street, a cluttered desk, a crowded conference hall—each scene contains dozens of objects that gleam, flicker, or stand out against their surroundings, competing for attention whether or not they matter to the task at hand. Psychologists have long known that people can, to a surprising degree, ignore these distractions. What has remained stubbornly unclear is exactly how that ignoring works when the distracting feature is unknown in advance, and whether the physical strength of the distraction—its salience—changes the brain’s ability to shut it down. A new study published in Attention, Perception, & Psychophysics by Yun Sun, Qi Zhang, Yuhan Xu, and Shuyan Chen of Minnan Normal University provides some of the clearest answers yet, and its central finding is counterintuitive: weaker distractions can actually be suppressed more strongly than loud ones.

To understand the study, it helps to know how thinking about attentional control has evolved. For decades, the dominant view held that attention is a two-stage system: a fast, automatic, stimulus-driven process that gets grabbed by anything visually conspicuous, followed by a slower, goal-driven process that steers attention toward what the observer is looking for. On this account, a red item in a field of green ones—a so-called color singleton—should capture attention almost involuntarily. But starting in the mid-2010s, evidence accumulated for a third possibility: active suppression. In this framework, the brain does not merely fail to be captured; it can proactively dampen the neural signal of known distractors before they seize control. Electrophysiological work identified a signature called the distractor positivity, an event-related brain potential component that appears when a salient item is successfully inhibited rather than attended.

The twist that the new study builds on concerns what can be suppressed. Earlier research suggested people could learn to suppress a specific color if it repeatedly proved distracting. But more recent experiments using what researchers call the majority search paradigm showed something stranger. In this task, participants search for a target among many same-colored items while one differently colored distractor may appear; crucially, the distractor’s color varies unpredictably across trials. If observers could only suppress a learned color, this variable distractor should capture attention. Instead, search was actually faster on trials containing the singleton distractor—a facilitation effect interpreted as evidence that the distractor had been suppressed before it could interfere. Because participants did not know which color would appear, the suppression could not be based on first-order information such as a specific hue. It had to operate on second-order information—the fact that one item is unique—or on global salience signals.

That discovery raised the question the Chinese team set out to answer: does the degree of salience matter for this higher-order mechanism? Salience, in the technical sense, refers to how strongly an item differs from its surround—how much it pops out. A high-contrast red circle among gray ones pops out dramatically; a barely darker gray circle among light gray ones barely registers. If second-order suppression simply tags any unique item and quiets it, salience should be irrelevant. But if suppression strength depends on how loud the distraction signal is, then salience should modulate the effect. Two competing accounts had already been skirmishing in the literature: one line of work argued that suppression is most effective for low-salience distractors, while other findings showed that even highly salient distractors can be proactively suppressed, arguing against the low-salience interpretation.

The researchers designed four experiments to disentangle these accounts, and all materials, data, and preregistered hypotheses were made publicly available on the Open Science Framework—a methodological transparency that has become a hallmark of rigorous attention research. Experiment 1 used the majority search paradigm and manipulated salience through set size, the number of items in the search display. In a singleton detection framework, a unique item among four items is more conspicuous than a unique item among eight, because salience is fundamentally relative. The result was striking in its null effect: higher-order suppression was essentially equivalent across set sizes, with comparable search facilitation whether the singleton stood among few or many items. Relative salience computed this way, at least, did not change the suppression benefit.

Experiments 2 and 3 shifted to the capture-probe paradigm, a more sensitive tool for measuring where attention actually goes. On each trial, after the search display, a probe appears and participants must report it; accuracy at the distractor’s location indexes whether attention was captured by or suppressed at that spot. Critically, the team manipulated the singleton’s color contrast, creating high-salience and low-salience distractors whose specific colors remained unpredictable. The results demonstrated that participants proactively suppressed singleton distractors based purely on second-order salience information—but, remarkably, the suppression was stronger for the low-salience singletons. The brain, it seemed, muted the quiet interloper more thoroughly than the blaring one.

Could this surprising asymmetry be an artifact of a weak manipulation? Experiment 4 addressed that concern with a psychophysical oddball detection task, in which participants simply judged whether any unique item was present in the display. Performance on this task validated that the high- and low-salience singletons genuinely differed in detectability and pop-out, ruling out the possibility that the salience manipulation had failed. The experiment also added eye tracking, allowing the researchers to examine oculomotor suppression—whether the eyes themselves avoided the singleton region differently depending on its salience. The eye-movement data provided converging evidence, showing how overt orienting was shaped by the same salience manipulation, and the luminance-contrast manipulation again produced the key result: stronger suppression of low-salience singletons compared to high-salience ones.

The theoretical implications cut deep. If suppression were a simple reflexive quenching of whatever signal is loudest, high-salience distractors should attract more inhibitory resources, not fewer. The observed advantage for weak singletons instead suggests that second-order suppression operates within functional limits: extremely salient items generate such strong attention-orienting signals that the suppression mechanism, even when engaged, cannot fully neutralize them, whereas moderate items fall comfortably within the mechanism’s effective range. This fits with a broader picture in which active suppression is a genuine top-down process with finite capacity, distinct from both passive filtering and learned feature-specific inhibition. It also aligns with electrophysiological findings that failed suppression of salient stimuli precedes behavioral errors—when the mechanism is overwhelmed, capture and mistakes follow.

There are also practical echoes beyond the laboratory. Drivers filtering billboards from traffic signs, radiologists scanning medical images for a lone anomaly, air traffic controllers monitoring crowded displays—all perform searches in which distracting singletons must be ignored without knowing their exact appearance in advance. The finding that suppression efficiency varies with distractor salience suggests that interface designers might reduce distraction not only by eliminating conspicuous clutter but by understanding that moderately conspicuous elements may be the ones the visual system handles best, while the loudest items are paradoxically the hardest to silence completely.

As the authors conclude, salience level emerges as a genuine potential factor influencing attentional suppression rather than an incidental detail of experimental design. The study extends the second-order suppression account from a demonstration that unique-but-unknown distractors can be suppressed to a characterization of when that suppression succeeds most fully. Future work, the researchers and their colleagues suggest, will need to trace the neural time course of these salience-dependent effects and determine how they interact with expectations, reward history, and working memory capacity. For now, the message is clear: the brain’s quieting of distraction is neither automatic nor uniform, and in the contest between attention and interruption, the loudest distractors retain a stubborn edge.

Subject of Research: How visual salience influences second-order attentional suppression of salient distractors

Article Title: The role of singleton salience in second-order suppression

Article References: Sun, Y., Zhang, Q., Xu, Y., & Chen, S. (2026). The role of singleton salience in second-order suppression. Attention, Perception, & Psychophysics, 88(7), Article 196. https://doi.org/10.3758/s13414-026-03331-7

Image Credits: AI Generated

DOI: 10.3758/s13414-026-03331-7

Keywords: visual attention, attentional suppression, salience, visual search, singleton distractors, second-order suppression, eye movements, cognitive control, color perception, inhibition, psychophysics, proactive suppression