Why a harder search can mean less distractor processing
The core idea behind perceptual load is that attention has a limited budget. When a task demands more of that budget, less is left over for things outside the target, so distractors get processed less. In a multi-target visual search, high perceptual load was associated with poorer search performance, slower detection of an unrelated auditory signal, and longer fixation durations, while eye-movement amplitude did not consistently change [3]. That pattern is consistent with a narrower attentional state under load: people keep their eyes stiller and take in less of what is outside the search focus.
The same narrowing shows up in how people handle distractors that are grouped together. In a search task where distractors could be large or small relative to the target, both autistic and typically developing participants were faster when target and distractor sizes were inconsistent, which the authors interpret as distractor grouping improving search efficiency [1]. Under high load, though, that grouping benefit was weaker in the autistic group than in the typically developing group, while no significant group difference appeared under low load [1]. In other words, load did not simply switch distractor rejection on; it changed how much a grouping cue could help, and that change differed between groups.
A busy working memory is not the same as a perceptually demanding search
It is tempting to assume that any extra mental load will sharpen filtering. The evidence does not support that. When people searched for targets while also holding items in visual working memory, recognition of distractors was only marginally improved compared with search without the extra memory demand, and repeating targets to reduce memory demands did not reduce distractor recognition either [2]. The authors concluded that widening the attentional set, not using working-memory resources in general, is what matters for incidental encoding of distractors [2].
A separate dual-task study points the same way. Searching for a novel target among familiar distractors was no less efficient when a visual working-memory task was added, and the authors argue that distractor familiarity, not the extra memory load, is what drives search efficiency in that setting [5]. Together these results suggest that perceptual load and working-memory load are not interchangeable: making the search itself harder changes distractor handling, while loading memory alongside an unchanged search does not reliably do so [2][5].
What load does not settle: salience, familiarity, and who is searching
Load also interacts with what the distractors themselves are like. A hybrid visual-search-and-flanker study set out to test how perceptual load and distractor salience interact, on the premise that distractor processing is mediated by load levels [4]. That framing fits the broader picture that load modulates rather than abolishes distractor processing, but the available summary does not report which salience conditions changed the size of the effect, so the practical answer for a highly salient distractor remains open.
Who is doing the searching matters too. The autism study found that the autistic group searched more slowly overall than typically developing controls, and that the high-load advantage from distractor grouping was smaller in the autistic group [1]. The authors read that as consistent with weak central coherence theory, a proposal about a processing style that favors local detail over global grouping. That is an interpretation rather than a demonstrated cause, and it applied to a specific size-grouping manipulation rather than to distractor rejection in general [1].
Putting it together, the useful answer for a reader is conditional. If you want people to filter out distractors, make the target task genuinely demanding rather than merely adding a memory chore, and expect the benefit to depend on how the distractors are grouped and who is doing the task [1][2][3].
Sources used in this answer
The Impact of Perceptual Load and Distractors’ Perceptual Grouping on Visual Search in ASD
In a visual search comparison, autistic participants searched more slowly than typically developing controls, distractor grouping improved search efficiency in both groups, and the grouping benefit under high perceptual load was weaker in the autistic group.
Visual working memory load plays limited, to no role in encoding distractor objects during visual search
Across four experiments, visual working-memory load during visual search produced only marginal improvement in incidental recognition of distractors, suggesting that widening the attentional set rather than occupying working memory drives distractor encoding.
Establishing gaze markers of perceptual load during multi-target visual search
High perceptual load in a multi-target visual search was associated with poorer search performance, slower detection of an auditory signal, and longer fixation durations, while saccade amplitude did not consistently change.
Investigating Stimulus Salience and Perceptual Load Interaction Using a Hybrid Visual Search-Flanker Task
A hybrid visual search-flanker study examined how perceptual load and distractor salience interact, on the premise that distractor processing is mediated by perceptual load levels.
Target familiarity and visual working memory do not influence familiarity effect in visual search
Adding a visual working-memory dual task did not change the efficiency of searching for a novel target among familiar distractors, supporting distractor familiarity rather than extra memory load as the key factor.