Proactive Suppression Research Articles

Proactive suppression is an implicit process that cannot be summoned on demand.

We examined whether proactive suppression can be applied on demand. A prompt cue indicated the to-be-ignored distractor color for each trial. Participants needed to use this cue to know which of two target shapes to respond to. To assess proactive suppression of the cued distractor color, we presented a probe letter recall task on a minority (25%) of the trials. A letter appeared inside each of the six shapes of the search array and participants recalled as many letters as they could. When the to-be-ignored color was fixed in Experiment 1, probe recall accuracy was lower for probe letters inside to-be-ignored-color distractors than target-color distractors, known as the probe suppression effect. However, when the prompted to-be-ignored color varied from trial to trial, the probe suppression effect disappeared, regardless of whether the prompt was a colored circle (Experiment 2) or a colored word (Experiment 3). Experiment 4 tested the search and destroy hypothesis by shortening the search display duration from 200 to 50 ms. No capture effect by the to-be-ignored color was evident, suggesting that participants did not first search for the to-be-ignored color, prior to suppressing it. We conclude that when rejection of a distractor color is required on demand, one cannot accomplish such suppression proactively but instead must deal with the distractor reactively, incurring a large cost in performance. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Proactive suppression is evident even if the probe-recognition assumption is not evident: complementary relationship between proactive and reactive suppression

ABSTRACT In capture-probe paradigms, probes presented in salient distractors are less frequently recognized than probes in non-salient distractors. This probe-recognition frequency effect could be due to attention going less frequently towards the salient distractors (proactive suppression) and/or dwelling more shortly on the salient distractors (reactive suppression). However, the probe-recognition frequency effect was considered as evidence supporting only proactive suppression based on the probe-recognition assumption where if attention is directed towards the probes, their correct identification should occur irrespective of whether attention disengages quickly or slowly. The present study revealed less accurate probe-recognition in the salient than non-salient distractors, inconsistent with the assumption and consistent with reactive suppression. To examine proactive suppression despite the assumption invalid, we measured how frequently the probes were attended by asking participants to always attempt the probe tests wherever they saw them, irrespective of whether they were able to recognize the attended probes or not. This probe-detection frequency showed less frequent attention towards the salient than non-salient distractors. The present findings suggest that proactive suppression is evident even if the probe-recognition assumption is not evident, and proactive and reactive suppression operate in concert to reduce the processing of distracting information.

Feature-based attentional control for distractor suppression.

To investigate whether attentional suppression is merely a byproduct of target facilitation or a result of independent mechanisms for distractor suppression, the present study examined whether attentional suppression takes place when target facilitation hardly occurs using a spatial cueing paradigm. Participants searched for target letters that were not red, i.e., a negative color. On each trial, a target color was randomly chosen among 12 colors to prevent establishing attentional control for target colors and to reduce intertrial priming for target colors. Immediately before a target display, a noninformative spatial cue was presented at one of the possible target locations. The cue was rendered in a negative color, which was to be ignored, to detect targets or the reference color, which was never presented for target and non-target letters. Experiment 1showed that negative color cues captured attention less than reference color cues, suggesting feature-based attentional suppression. The suppression effect was replicated when the temporal interval between the onsets of the cue and target displays was reduced in Experiments 2and 3, suggesting proactive suppression. Experiment 3directly confirmed no attentional control settings for target colors and intertrial priming. These findings suggest that distractor features can guide attention at the pre-attentive stage when target features are not used to attend to targets.

Evidence that proactive distractor suppression does not require attentional resources.

Does the suppression of irrelevant visual features require attentional resources? McDonald et al. (2023, Psychonomic Bulletin & Review, 30, 224-234) proposed that suppression processes are unavailable while a person is busy performing another task. They reported the absence of the PD (believed to index suppression) when two tasks were presented close together in time. We looked for converging evidence using established behavior measures of suppression. Following McDonald et al., our participants performed a rapid serial visual presentation (RSVP) task followed by a search task. For the RSVP task, participants determined whether the target digit 4 or 6 appeared within a string of other digits. The search display appeared at a lag of 2 or 8 digits after the RSVP target. Participants searched for a yellow target circle amongst nine background circles, which included a uniquely colored distractor for some trials. The main question was whether distractor suppression would occur at Lag 2, while attentional resources were still processing the RSVP target. Suppression was assessed using the capture-probe paradigm. On 30% of trials, probe letters appeared inside the colored circles and participants reported those letters. Probe recall accuracy was lower at locations with distractor colors than those with neutral colors (the baseline), suggesting proactive suppression. Critically, this difference in probe recall accuracy was similar at Lag 2 and Lag 8, suggesting that the ability to proactively suppress distractors remains intact while dual-tasking. We argue that although reactive suppression likely requires attentional resources, proactive suppression-an implicit process-does not.

Proactive suppression can be applied to multiple salient distractors in visual search.

There is a growing body of research demonstrating that the capture of attention by a single salient distractor can be prevented via proactive suppression. In real-world contexts, there are often several distracting events that compete for attention, but it is entirely unknown whether multiple objects can be suppressed concurrently. We used behavioral and electrophysiological measures to investigate the existence and time course of multiple-item suppression. We employed search displays that contained either one or two uniquely colored distractors that differed in their salience (S+ and S-), or no such distractors. Search performance improved with the number of salient distractors, indicating that the suppression of multiple items reduced the effective display set size. This was also the case when the target color was no longer fully predictable, ruling out an alternative explanation in terms of attentional guidance by target templates. In an experiment where S+ and S- always appeared together in the same display, the PD component (a marker of proactive suppression) was triggered exclusively by the more salient distractor (S+), indicative of single-item suppression. However, when displays with one or both salient distractors were intermixed, a reliable PD component was also triggered by S-, even when it was accompanied by S+ in the same display. These results show that multiple concurrent salient signals can be proactively inhibited. They demonstrate that signal suppression processes can be adaptively employed to counteract visual distraction at different locations, in order to facilitate the attentional selection of relevant objects in crowded visual environments. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Learned spatial suppression is not always proactive.

Learning to ignore distractors is critical for navigating the visual world. Research has suggested that a location frequently containing a salient distractor can be suppressed. How does such suppression work? Previous studies provided evidence for proactive suppression, but methodological limitations preclude firm conclusions. We sought to overcome these limitations with a new search-probe paradigm. On search trials, participants searched for a shape oddball target while a salient color singleton distractor frequently appeared in a high-probability location. On randomly interleaved probe trials, participants discriminated the orientation of a tilted bar presented briefly at one of the search locations, allowing us to index the spatial distribution of attention at the moment the search would have begun. Results on search trials replicated previous findings: reduced attentional capture when a salient distractor appeared in the high-probability location. However, critically, probe discrimination was no different at the high-probability and low-probability locations. We increased the incentive to ignore the high-probability location in Experiment 2 and found, strikingly, that probe discrimination accuracy was greater at the high-probability location. These results suggest that the high-probability location was initially selected before being suppressed, consistent with a reactive mechanism. Overall, the accuracy probe procedure demonstrates that learned spatial suppression is not always proactive, even when response time metrics seem consistent with such an inference. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Global enhancement of target color-not proactive suppression-explains attentional deployment during visual search.

The current study touches on a central debate in the area of attention: how the human brain handles distraction by salient stimuli. The idea of proactive suppression proposes a new fundamental perceptual mechanism to resolve this question, whereby attentional capture by a task-irrelevant salient distractor can be preempted through top-down inhibitory mechanisms. In this study, we replicate empirical effects underlying this claim, but show that they are better explained by an alternative mechanism, global target-feature enhancement. Identical to original studies using a capture-probe dual-task design, observers recalled fewer letters superimposed upon color singleton distractors, relative to other irrelevant search items (fillers). However, given that fillers (but not singleton distractors) always matched the color of the target, this effect could have been due to global featural attention to the target color rather than suppression of the singleton distractor. After manipulating the color of fillers such that they no longer matched the target color, probe recall associated with these was reduced, causing the relative "suppression" of singleton distractors to be abolished. We then manipulated the color similarity of targets and fillers, and found that filler probe recall was graded as a function of this color similarity, even within a single search context. This strongly suggests that increased attention to fillers due to global target color enhancement underlies the difference in attention among distractor items, not proactive distractor suppression. In contrast with feature enhancement and reactive suppression, the proposed proactive suppression mechanism still lacks convincing behavioral evidence. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Age-related differences in the statistical learning of target selection and distractor suppression.

In recent years, the use of implicit mechanisms based on statistical learning (SL) has emerged as a strong factor in biasing visuospatial attention, so that target selection is improved at frequently attended locations and distractor filtering is facilitated at frequently suppressed locations. Although these mechanisms have been consistently described in younger adults, similar evidence in healthy aging is scarce. Therefore, we studied the learning and persistence of SL of target selection and distractor suppression in younger and older adults in visual search tasks where the frequency of target (Experiment 1) or distractor (Experiment 2) was biased across spatial locations. The results show that SL of target selection was preserved in the older adults so, similar to their younger counterparts, they showed a strong and persistent advantage in target selection at locations more frequently attended. However, unlike young adults, they did not benefit from implicit SL of distractor suppression, so that distractor interference was maintained throughout the experiment independently of the contingencies associated with distractor locations. Taken together, these results provide novel evidence of distinct developmental patterns for SL of task-relevant and task-irrelevant visual information, likely reflecting differences in the implementation of proactive suppression attentional mechanisms between younger and older adults. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Asymmetric learning of dynamic spatial regularities in visual search: Robust facilitation of predictable target locations, fragile suppression of distractor locations.

Static statistical regularities in the placement of targets and salient distractors within the search display can be learned and used to optimize attentional guidance. Whether statistical learning also extends to dynamic regularities governing the placement of targets and distractors on successive trials remains controversial. Here, we applied the same dynamic cross-trial regularity-one-step shift of the critical item in clockwise/counterclockwise direction-to either the target or a distractor. In two experiments, we found and replicated robust learning of the predicted target location: processing of the target at this location was facilitated, compared to random target placement. But we found little evidence of proactive suppression of the predictable distractor location-even in a close replication of Wang et al. (2021), who had reported a dynamic distractor suppression effect. Facilitation of the predictable target location was associated with explicit awareness of the dynamic regularity, whereas participants showed no awareness of the distractor regularity. We propose that this asymmetry arises because, owing to the target's central role in the task set, its location is explicitly encoded in working memory, enabling the learning of dynamic regularities. In contrast, the distractor is not explicitly encoded; so, statistical learning of dynamic distractor locations is more precarious. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

On preventing capture: Does greater salience cause greater suppression?

It has been proposed that salient objects have high potential to disrupt target performance, and so people learn to proactively suppress them, thereby preventing these salient distractors from capturing attention in the future. Consistent with this hypothesis, Gaspar et al. (Proceedings of the National Academy of Sciences, 113(13), 3693-3698, 2016) reported that the PD (believed to index suppression) was larger for high-salient color distractors than for low-salient color distractors. The present study looked for converging evidence that salience triggers suppression using established behavior measures of suppression. Following Gaspar et al., our participants searched for a yellow target circle among nine background circles, which sometimes included one circle with a unique color. The distractor was either high or low in salience with respect to the background circles. The question was whether the high-salient color would be proactively suppressed more strongly than the low-salient color. This was assessed using the capture-probe paradigm. On 33% of trials, probe letters appeared inside colored circles and participants were to report those letters. If high-salient colors are more strongly suppressed, then probe recall accuracy should be lower at locations with the high-salient color than those with the low-salient color. Experiment 1found no such effect. A similar finding was observed in Experiment 2after addressing possible floor effects. These findings suggest that proactive suppression is not caused by salience. We propose that the PD reflects not only proactive suppression but also reactive suppression.

Suppression of distracting inputs by visual-spatial cues is driven by anticipatory alpha activity.

A growing body of research demonstrates that distracting inputs can be proactively suppressed via spatial cues, nonspatial cues, or experience, which are governed by more than one top-down mechanism of attention. However, how the neural mechanisms underlying spatial distractor cues guide proactive suppression of distracting inputs remains unresolved. Here, we recorded electroencephalography signals from 110 participants in 3 experiments to identify the role of alpha activity in proactive distractor suppression induced by spatial cues and its influence on subsequent distractor inhibition. Behaviorally, we found novel changes in the spatial proximity of the distractor: Cueing distractors far away from the target improves search performance for the target, while cueing distractors close to the target hampers performance. Crucially, we found dynamic characteristics of spatial representation for distractor suppression during anticipation. This result was further verified by alpha power increased relatively contralateral to the cued distractor. At both the between- and within-subjects levels, we found that these activities further predicted the decrement of the subsequent PD component, which was indicative of reduced distractor interference. Moreover, anticipatory alpha activity and its link with the subsequent PD component were specific to the high predictive validity of distractor cue. Together, our results reveal the underlying neural mechanisms by which cueing the spatial distractor may contribute to reduced distractor interference. These results also provide evidence supporting the role of alpha activity as gating by proactive suppression.

Supplemental Material for Proactive Suppression Can Be Applied to Multiple Salient Distractors in Visual Search

Supplemental Material for Proactive Suppression Can Be Applied to Multiple Salient Distractors in Visual Search

Proactive suppression of learned distractor features

Proactive suppression of learned distractor features

Dynamics of attentional allocation to targets and distractors during visual search

There is much debate about the neural mechanisms that achieve suppression of salient distracting stimuli during visual search. The proactive suppression hypothesis asserts that if exposed to the same distractors repeatedly, these stimuli are actively inhibited before attention can be shifted to them. A contrasting proposal holds that attention is initially captured by salient distractors but is subsequently withdrawn. By concurrently measuring stimulus-driven and intrinsic brain potentials in 36 healthy human participants, we obtained converging evidence against early proactive suppression of distracting input. Salient distractors triggered negative event-related potentials (N1pc/N2pc), enhanced the steady-state visual evoked potential (SSVEP) relative to non-salient (filler) stimuli, and suppressed contralateral relative to ipsilateral alpha-band amplitudes—three electrophysiological measure associated with the allocation of attention—even though these distractors did not interfere with behavioral responses to the search targets. Furthermore, these measures indicated that both stimulus-driven and goal-driven allocations of attention occurred in conjunction with one another, with the goal-driven effect enhancing and prolonging the stimulus-driven effect. These results provide a new perspective on the traditional dichotomy between bottom-up and top-down attentional allocation. Control experiments revealed that continuous marking of the locations at which the search display items were presented resulted in a dramatic and unexpected conversion of the target-elicited N2pc into a shorter-latency N1pc in association with faster reaction times to the targets.

What the Flip? What the P-N Flip Can Tell Us about Proactive Suppression.

It has been debated whether salient distractors in visual search can be proactively suppressed to completely prevent attentional capture, as the occurrence of proactive suppression implies that the initial shift of attention is not entirely driven by physical salience. While the presence of a Pd component in the EEG (associated with suppression) without a preceding N2pc component (associated with selection) has been used as evidence for proactive suppression, the link between these ERPs and the underlying mechanisms is not always clear. This is exemplified in two recent articles that observed the same waveform pattern, where an early Pd-like component flipped to a N2pc-like component, but provided vastly different interpretations (Drisdelle, B. L., & Eimer, E. PD components and distractor inhibition in visual search: New evidence for the signal suppression hypothesis. Psychophysiology, 58, e13898, 2021; Kerzel, D., & Burra, N. Capture by context elements, not attentional suppression of distractors, explains the PD with small search displays. Journal of Cognitive Neuroscience, 32, 1170-1183, 2020). Using RAGNAROC (Wyble et al., Understanding visual attention with RAGNAROC: A Reflexive Attention Gradient through Neural AttRactOr Competition. Psychological Review, 127, 1163-1198, 2020), a computational model of reflexive attention, we successfully simulated this ERP pattern with minimal changes to its existing architecture, providing a parsimonious and mechanistic explanation for this flip in the EEG that is unique from both of the previous interpretations. Our account supports the occurrence of proactive suppression and demonstrates the benefits of incorporating computational modeling into theory building.

Attenuating the ‘attentional white bear’ effect enhances suppressive attention

Trying to ignore an object can bias attention towards it – a phenomenon referred to as the ‘attentional white bear’ (AWB) effect. The mechanisms behind this effect remain unclear. On one hand, the AWB may reflect reactive, ‘search and destroy’ distractor suppression, which directs attention toward irrelevant objects in order to suppress further attention to them. However, another possibility is that the AWB results from failed proactive distractor suppression – attempting to suppress attention to an irrelevant object from the outset may inadvertently result in an attentional shift towards it. To distinguish these two possibilities, we developed a categorical visual search task that addresses limitations present in prior studies. In five experiments (Ntotal = 96), participants searched displays of naturalistic stimuli cued only with distractor categories (targets were unknown and unpredictable). We observed an AWB and later attenuated it by presenting a pre-search stimulus, likely disrupting guidance from distractor templates in working memory. We conclude that the AWB resulted from a failure of proactive suppression rather than a search and destroy process.

Does superior visual working memory capacity enable greater distractor suppression?

ABSTRACT We asked whether individuals high in working memory capacity have a superior ability to proactively suppress features. If so, it would help explain why these individuals are more resistant to attention capture. We tested this hypothesis using the capture-probe paradigm employed in Lien et al. (2022. On preventing attention capture: Is singleton suppression actually singleton suppression? Psychological Research, 86(6), 1958–1971). Participants (N = 112) performed a colour change detection task, assessing visual working memory capacity. They then performed a visual search task (70% of the trials) intermixed with probe tasks (30% of the trials). For the visual search task, either a salient colour singleton distractor or non-salient distractor (a triplet) appeared with the target object. For the probe recall task, participants reported probe letters that briefly appeared inside each object. Replicating Lien et al., a suppression effect on probe recall accuracy was observed for both salient singletons and non-salient triplets. Critically, high and low visual working memory capacity individuals showed statistically equivalent ability to suppress colour distractors. These findings suggest that proactive suppression is not the mechanism by which high-capacity individuals achieve greater resistance to capture. Proactive suppression may be an implicit process that does not require special working memory capabilities.

Action suppression reveals opponent parallel control via striatal circuits.

The direct and indirect pathways of the basal ganglia are classically thought to promote and suppress action, respectively1. However, the observed co-activation of striatal direct and indirect medium spiny neurons2 (dMSNs and iMSNs, respectively) has challenged this view. Here we study these circuits in mice performing an interval categorization task that requires a series of self-initiated and cued actions and, critically, a sustained period of dynamic action suppression. Although movement produced the co-activation of iMSNs and dMSNs in the sensorimotor, dorsolateral striatum (DLS), fibre photometry and photo-identified electrophysiological recordings revealed signatures of functional opponency between the two pathways during action suppression. Notably, optogenetic inhibition showed that DLS circuits were largely engaged to suppress-and not promote-action. Specifically, iMSNs on a given hemisphere were dynamically engaged to suppress tempting contralateral action. To understand how such regionally specific circuit function arose, we constructed a computational reinforcement learning model that reproduced key features of behaviour, neural activity and optogenetic inhibition. The model predicted that parallel striatal circuits outside the DLS learned the action-promoting functions, generating the temptation to act. Consistent with this, optogenetic inhibition experiments revealed that dMSNs in the associative, dorsomedial striatum, in contrast to those in the DLS, promote contralateral actions. These data highlight how opponent interactions between multiple circuit- and region-specific basal ganglia processes can lead to behavioural control, and establish a critical role for the sensorimotor indirect pathway in the proactive suppression of tempting actions.

Unseeing the white bear: Negative search criteria guide visual attention through top-down suppression.

In three spatial cueing experiments, we investigated whether a negative search criterion (i.e., a task-relevant feature that negatively defines the target) can guide visual attention in a top-down manner. Our participants searched for a target defined by a negative feature (e.g., red if the target was a nonred horizontal bar). Before the target, a peripheral singleton cue was shown at the target position (valid condition) or a nontarget position (invalid condition). We found slower reaction times in valid than invalid trials only with singleton cues matching the negative feature. Importantly, we ruled out that participants searched for target-associated features instead of suppressing the negative feature (Experiment 1). Furthermore, we demonstrated that suppression of cues with a negative feature was stronger than mere ignorance of singleton cues with a task-irrelevant feature. Finally, cue-target intervals of 60 ms and 150 ms elicited the same suppression effects for cues matching the negative feature. These findings suggest that the usage of a negative search criterion elicited feature-selective proactive suppression (Experiments 2 and 3). Thus, our results provide first evidence of top-down attentional suppression dependent on current task goals as a strategy operating in parallel to the goal-directed search for target-defining features (Experiment 2). (PsycInfo Database Record (c) 2022 APA, all rights reserved).

No evidence for proactive suppression of explicitly cued distractor features.

Visual search benefits from advance knowledge of nontarget features. However, it is unknown whether these negatively cued features are suppressed in advance (proactively) or during search (reactively). To test this, we presented color cues varying from trial-to-trial that predicted target or nontarget colors. Experiment 1 (N = 96) showed that both target and nontarget cues speeded search. To test whether attention proactively modified cued feature representations, in Experiment 2 (N = 200), we interleaved color probe and search trials and had participants detect the color of a briefly presented ring that could either match the cued color or not. People detected positively cued colors better than other colors, whereas negatively cued colors were detected no better or worse than other colors. These results demonstrate that nontarget features are not suppressed proactively, and instead suggest that anticipated nontarget features are ignored via reactive mechanisms.