Salient, task-irrelevant stimuli that consistently appear with the same defining feature (e.g., a specific color) can be actively downweighted by the visual system. This attentional suppression mechanism has been shown to benefit visual search: Search targets are more efficiently located in displays with a salient color singleton distractor than in displays without a distractor. The singleton presence benefit has been commonly attributed to reduced allocation of attention to the location of the distractor. We question here whether suppression merely excludes locations for attentional selection, or whether the suppressive mechanism fundamentally alters the representation of other elements in the scene. To examine this question, we assessed the effects of suppression on nearby elements by perceptually grouping sets of elements together in the search array. On different trials, the search target either appeared in the same perceptual group as a to-be-suppressed color singleton distractor, at an equidistant location but in a different group, or at a more distant location in a different group. Experiment 1 showed that selection of the target was enhanced when it was grouped with a suppressed distractor. Experiment 2 varied the locations grouped together from trial to trial, and also demonstrated a same-group benefit. To test whether participants strategically prioritized the group containing the salient distractor (because it had fewer potential target elements), Experiment 3 changed the number of elements in each group. Target selection was enhanced when grouped with the distractor even when the distractor-containing group had more items to search. Consistent with the effects of grouping, a benefit of closer target-distractor distance was also observed in the experiments. Together the results reveal the novel finding that attentional suppression facilitates selection of stimuli near the distractor, implying that distractor downweighting may be achieved by biasing the competition for representation in favor of surrounding locations.
Recent findings have shown that people are capable of proactively inhibiting salient visual distractors in a scene when they know the color of the distractor, enhancing efficient search. Investigations of this suppression effect have concluded that it is not possible to suppress a distractor of an unknown color, implying a mechanism that operates only on a first-order, feature-specific level. However, with a modification to the search task, we show here for the first time that people can indeed suppress salient uniquely colored distractors even when not knowing their color in advance. The task requires participants to search for the most prevalent of several shapes in the display. In two experiments the presence of an unpredictable-color singleton facilitated search. An experiment with briefly presented probes confirmed proactive prevention of capture by the distractor. The results reveal a second-order or global-salience-based suppressive mechanism that facilitates visual processing. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
Recent findings suggest that it is possible for people to proactively avoid attentional capture by salient distractors during visual search. The results have important implications for understanding the competing influences of top-down and bottom-up factors in visual attention. Nevertheless, questions remain regarding the extent to which apparently ignored distractors are processed. To assess distractor processing, previous experiments have used a probe method in which stimuli are occasionally superimposed on the search display-requiring participants to abort the search and identify the probe stimuli. It has been recently shown that such probe tasks may be vulnerable to decision-level biases, such as a participant's willingness to report stimuli on to-be-ignored items. We report here results from a new method that is not subject to this limitation. In the new method, the non-target search elements, including the salient distractors, contained features that were either congruent or incongruent with the target. Processing of the non-target elements is inferred from the effects of the compatibility of the shared features on judgments about the target. In four experiments using the technique we show that ignored salient distractors are indeed processed less fully than non-target elements that are not salient, replicating the results of earlier studies using the probe methods. Additionally, the processing of the distractors was found to be reduced at least in part at early perceptual or attentional stages, as assumed by models of attentional suppression. The study confirms the proactive avoidance of capture by salient distractors measured without decision-level biases and provides a new technique for assessing the magnitude of distractor processing.
Visual features associated with reward involuntarily capture attention. This value-driven attentional capture effect is believed to occur even when the rewarded stimuli are irrelevant to task demands. However, almost all existing studies presented the rewarded stimuli at or near potential target locations, making them spatially relevant to the observer. To more thoroughly examine the attentional priority of reward-associated stimuli independently of spatial task relevance, in three experiments we followed reward training with a rapid serial visual presentation (RSVP) task. In the RSVP task, participants identified a letter in a specified target color among a centrally-presented letter stream, while attempting to ignore a flanker distractor in the periphery. The timing of the flanker relative to the central target was manipulated. Previous research has shown that if a flanker captures attention, it will lead to greater cost in target identification when it shortly precedes the target, compared to simultaneous presentation. In all three experiments a previously rewarded flanker did not capture attention at task-irrelevant peripheral locations, while distractors in the goal-matching color did capture attention at the same eccentricity. To confirm that the color-reward association was retained during the RSVP task, Experiment 3 included interspersed blocks of an additional singleton task, a traditional test of value-driven attentional capture that presents the rewarded stimuli at potential target locations, with blocks of the RSVP task. The additional singleton task demonstrated significant capture by the rewarded stimuli throughout the session, verifying effective reward learning, despite the absence of value-driven capture in the RSVP task. The results reveal a modulating role of spatial task relevance in the attentional prioritization of reward-associated stimuli—rewarded stimuli do not capture attention at task-irrelevant locations.
When people make decisions about sequentially presented items in psychophysical experiments, their decisions are always biased by their preceding decisions and the preceding items, either by assimilation (shift towards the decision or item) or contrast (shift away from the decision or item). Such sequential biases also occur in naturalistic and real-world judgments such as facial attractiveness judgments. In this article, we aimed to cast light on the causes of these sequential biases. We first found significant assimilative and contrastive effects in a visual face attractiveness judgment task and an auditory ringtone agreeableness judgment task, indicating that sequential effects are not limited to the visual modality. We then found that the provision of trial-by-trial feedback of the preceding stimulus value eliminated the contrastive effect, but only weakened the assimilative effect. When participants orally reported their judgments rather than indicated them via a keyboard button press, we found a significant diminished assimilative effect, suggesting that motor response repetition strengthened the assimilation bias. Finally, we found that when visual and auditory stimuli were alternated, there was no longer a contrastive effect from the immediately previous trial, but there was an assimilative effect both from the previous trial (cross-modal) and the 2-back trial (same stimulus modality). These findings suggested that the contrastive effect results from perceptual processing, while the assimilative effect results from anchoring of the previous judgment and is strengthened by response repetition and numerical priming.
Efficient search of the environment requires that people attend to the desired elements in a scene and ignore the undesired ones. Recent research has shown that this endeavor can benefit from the ability to proactively suppress distractors with known features, but little is known about the mechanisms that produce the suppression. We show here in five experiments ( N = 120 college students) that, surprisingly, identification of a sought-for target is enhanced when it is grouped with a suppressed distractor compared with when it is in a different perceptual group. The results show that the suppressive mechanism not only downweights undesired elements but also enhances responses to task-relevant elements in competition for attention with the distractor, fine tuning the suppression. The findings extend the understanding of how people efficiently process their visual world.
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