Singleton Distractor Research Articles

Opposing effects of stimulus-driven and memory-driven attention in visual search

A recent study (Jung, Han, & Min, in press) reported that the extent to which attentional control is strained is a critical factor for observing stimulus-driven attentional capture in visual search. Expanding this study, we tested whether memory-driven attentional capture is also dependent on cognitive mechanism underlying visual search tasks. In our experiment, a group of participants performed a dual task, consisting of a working memory and a visual search task (memory-driven attention group), whereas the other performed only a visual search task (stimulus-driven attention group). Each group was further divided into two groups depending on the search task performed. For visual search tasks, we utilized two different search tasks; Landolt-C and orientation feature search tasks. For the former, participants searched for an outlined square with a top- or bottom-gap among left- or right-gap squares. For the latter, participants looked for a right- or left-tilted line among vertical lines. In a half of the total trials, a memory-matching/salient singleton distractor was present. In the remaining trials, no such a memory-matching/singleton distractor was present. As results, attentional capture by the singleton distractor was found under feature search task, p< .01. On the contrary, the task-irrelevant distractor did not capture when participants performed the Landolt-C search, p> .45. The memory-driven group showed a different pattern. A task-irrelevant, memory matching distractor captured attention when participants performed Landolt-C search task, p< .001. However, no memory-driven attentional capture was found under the feature search, p > .72. Our results demonstrate that the nature underlying visual search tasks is an important factor for observing both stimulus-driven and memory-driven attention. However, the specific patterns of the capture were opposite. These findings point to the role of interplay between the extent to which attentional control is strained and working memory in attentional capture.

Probing the Neural Mechanisms for Distractor Filtering and Their History-Contingent Modulation by Means of TMS

In visual search, the presence of a salient, yet task-irrelevant, distractor in the stimulus array interferes with target selection and slows down performance. Neuroimaging data point to a key role of the frontoparietal dorsal attention network in dealing with visual distractors; however, the respective roles of different nodes within the network and their hemispheric specialization are still unresolved. Here, we used transcranial magnetic stimulation (TMS) to evaluate the causal role of two key regions of the dorsal attention network in resisting attentional capture by a salient singleton distractor: the frontal eye field (FEF) and the cortex within the intraparietal sulcus (IPS). The task of the participants (male/female human volunteers) was to discriminate the pointing direction of a target arrow while ignoring a task-irrelevant salient distractor. Immediately after stimulus onset, triple-pulse 10 Hz TMS was delivered either to IPS or FEF on either side of the brain. Results indicated that TMS over the right FEF significantly reduced the behavioral cost engendered by the salient distractor relative to left FEF stimulation. No such effect was obtained with stimulation of IPS on either side of brain. Interestingly, this FEF-dependent reduction in distractor interference interacted with the contingent trial history, being maximal when no distractor was present on the previous trial relative to when there was one. Our results provide direct causal evidence that the right FEF houses key mechanisms for distractor filtering, pointing to a pivotal role of the frontal cortex of the right hemisphere in limiting interference from an irrelevant but attention-grabbing stimulus.SIGNIFICANCE STATEMENT Visually conspicuous stimuli attract our attention automatically and interfere with performance by diverting resources away from the main task. Here, we applied transcranial magnetic stimulation over four frontoparietal cortex locations (frontal eye field and intraparietal sulcus in each hemisphere) to identify regions of the dorsal attention network that help limit interference from task-irrelevant, salient distractors. Results indicate that the right FEF participates in distractor-filtering mechanisms that are recruited when a distracting stimulus is encountered. Moreover, right FEF implements adjustments in distraction-filtering mechanisms following recent encounters with distractors. Together, these findings indicate a different hemispheric contribution of the left versus right dorsal frontal cortex to distraction filtering. This study expands our understanding of how our brains select relevant targets in the face of task-irrelevant, salient distractors.

Opposing effects of stimulus-driven and memory-driven attention in visual search.

When one searches for a specific target in a cluttered visual scene, a perceptually salient stimulus or a stimulus that matches working memory's contents is prioritized for attentional selection. In the present study, we aimed at clarifying under which circumstance stimulus-driven attention or memory-driven attention is more pronounced. We hypothesized that one crucial factor affecting stimulus-driven versus memory-driven attention is how a concurrent visual search task is performed. To address this issue, we employed two visual search tasks whose underlying mechanisms are known to be different: Landolt-C search and orientation feature search. One group of participants performed visual search tasks containing a memory-matching stimulus, and the other group conducted searches in the presence of a salient singleton distractor. The results showed that the effects of stimulus-driven and memory-driven attention differed, depending on the cognitive mechanisms underlying the visual search tasks. A memory-matching stimulus captured attention when participants performed the Landolt-C search, whereas this capture was diminished under feature search. In contrast, capture by the salient singleton distractor was found only under feature search. These results demonstrate that the nature of the underlying visual search tasks is an important factor for observing stimulus-driven versus memory-driven attention. Our results also provide a potential solution to resolve current debate regarding memory-driven attention in visual search.

Statistical regularities bias overt attention

A previous study employing the additional singleton paradigm showed that a singleton distractor that appeared more often in one specific location interfered less with target search than when it appeared at any other location. These findings suggested that through statistical learning the location that was likely to contain a distractor was suppressed relative to all other locations. Even though feasible, it is also possible that this effect is due to faster disengagement of attention from the high-probability distractor location. The present study tested this hypothesis using a variant of the additional singleton task adapted for eye tracking in which observers made a speeded saccade to a shape singleton and gave a manual response. The singleton distractor was presented more often at one location than all other locations. Consistent with the suppression hypothesis, we found that fewer saccades landed at the high-probability distractor location than any other location. Also, when a target appeared at the high-probability location, saccade latencies towards the target were higher than latencies towards the target when it was presented at other locations. Furthermore, in addition to suppression, we also found evidence for faster disengagement from the high-probability distractor location than the low-probability distractor location; however, this effect was relatively small. The current findings support the notion that through statistical learning plasticity is induced in the spatial priority map of attentional selection so that the high-probability distractor location is suppressed compared to any other location.

Feature-based statistical regularities of distractors modulate attentional capture.

Ignoring salient distracting information is paramount to efficiently guiding attention during visual search. Learning to reject or suppress these strong sources of distraction leads to more effective visual search for targets. Participants can learn to overcome salient distractors if given reliable search regularities. If salient distractors appear in 1 location more frequently than any other, the visual system can use this environmental regularity to reduce attentional capture at the more frequent location (Wang & Theeuwes, 2018). We asked if reduced attentional capture is limited to location-based regularities, or, if the visual attentional system is configured to use feature-based regularities in reducing attentional capture as well. In 4 experiments examining attentional capture by task-irrelevant color singletons, participants searched for a shape singleton target among homogenously colored distractors. Critically, on a proportion of trials, a salient, color singleton distractor was presented. Color singleton distractors that appeared at a frequent location captured attention less than color singleton distractors that appeared at infrequent locations, replicating previous findings. In subsequent experiments we manipulated the frequency of the colors of the color singleton distractors and observed robust increases in capture based on color feature regularities. Despite strong location information, we observed reliable attentional capture attenuation by frequently presented distractor colors. Our results suggest that attentional capture is attenuated by both location and feature information. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Distinct prioritization of visual working memory representations for search and for recall.

Despite the inherent limitations of visual working memory (VWM), it effectively supports numerous everyday behaviors - capabilities that are due, in part, to its flexibility. An observer can flexibly prioritize VWM representations to support at least two behavioral outcomes: An item can be prioritized to enhance its representational quality, thereby enhancing recall precision, and an item can be granted "template status," allowing it to bias attention during visual search, speeding search for matching targets. Here we examined the relationship between these two forms of prioritization. Research has shown that a byproduct of granting an item template status is that its precision is enhanced; however, it is unclear if the inverse is also true: Does prioritizing an item for enhanced representational quality cause that item to bias attention? In the present study, participants remembered the colors of two squares for a subsequent recall task, and one was cued, indicating it was 80% likely to be the target of the memory test. To assess template status, a subset of trials ended in a visual search task in which a colored singleton distractor matched the color of the cued item in memory, the non-cued item, or an unrelated color. We found that, although the cue was effective at enhancing recall precision of the cued item, it had no systematic effect on which of the two memory items was granted template status. Thus, we conclude that the two forms of prioritization in VWM - prioritization for recall and for search - are distinct.

Evidence for second-order singleton suppression based on probabilistic expectations.

Decades of research in attention have shown that salient distractors (e.g., a color singleton) tend to capture attention. However, in most studies, singleton distractors are just as likely to be present as absent. We therefore have little knowledge of how probabilistic expectations of the salient distractor's occurrence and features affect suppression. In three experiments, we explored this question by manipulating the frequency of a singleton distractor and the variability of its color within a search display. We found that increased expectations regarding the occurrence of the singleton distractor eliminated the singleton response time cost and reduced the number of first saccades to the singleton. In contrast, expectations regarding variability in the singleton color did not affect singleton capture. This was surprising and suggests the ability to suppress second-order salience over and above that of first-order features. We next inserted the probe display that included a to-be-reported letter inside each shape between search trials to measure if attention went to multiple objects. The letter in the singleton location was reported less often in the high-frequency condition, suggesting proactive suppression of expected singleton. Additionally, we found that trial-to-trial repetitions of a singleton (irrespective of its color and location) facilitated performance (i.e., singleton repetition priming), but repetitions of its specific color or location did not. Together our findings demonstrate that attentional capture by a color singleton distractor is attenuated by probabilistic expectations of its occurrence, but not of its color and location. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Distract yourself: prediction of salient distractors by own actions and external cues

Distracting sensory events can capture attention, interfering with the performance of the task at hand. We asked: is our attention captured by such events if we cause them ourselves? To examine this, we employed a visual search task with an additional salient singleton distractor, where the distractor was predictable either by the participant’s own (motor) action or by an endogenous cue; accordingly, the task was designed to isolate the influence of motor and non-motor predictive processes. We found both types of prediction, cue- and action-based, to attenuate the interference of the distractor—which is at odds with the “attentional white bear” hypothesis, which states that prediction of distracting stimuli mandatorily directs attention towards them. Further, there was no difference between the two types of prediction. We suggest this pattern of results may be better explained by theories postulating general predictive mechanisms, such as the framework of predictive processing, as compared to accounts proposing a special role of action–effect prediction, such as theories based on optimal motor control. However, rather than permitting a definitive decision between competing theories, our study highlights a number of open questions, to be answered by these theories, with regard to how exogenous attention is influenced by predictions deriving from the environment versus our own actions.

A singleton distractor updates the inhibitory template for visual marking

Visual marking, which is based on the assumption that previewing some distractors increases the efficiency of subsequent visual searches, constitutes one of the most efficient inhibitions on visual searches. The preview search task consists of a display of a subset of distractors followed by an additional display containing the remaining distractors and a target. During the preview period, an inhibitory template is thought to be formed, resulting in the prioritization of the subsequently presented items and the inhibition of the previewed items. Although the previous studies have mainly examined the determinants that impair the inhibitory templates resulting in inefficient visual searches, the present study examined the possibility that the template could be updated to increase search efficiency. To this end, we used a preview search task and manipulated the presence of a singleton distractor in the display of the additional items. We examined whether the singleton increased the efficiency of the search performance by determining if the inhibitory template would be updated such that participants would treat the singleton as if it had been previewed. The results demonstrated that the response times were faster with the singleton included, suggesting that an inhibitory template for visual marking could be updated and lead to improved search performance.

The power of negative thinking: Paradoxical but effective ignoring of salient-but-irrelevant stimuli with a spatial cue

ABSTRACTA uniquely coloured singleton among other uniformly coloured stimuli can function as a powerful attractor of attention. However, top-down attentional mechanisms are also powerful, and there are circumstances in which they can suppress irrelevant distractors. The current study tested whether an endogenous spatial cue indicating the location of a salient colour singleton distractor can eliminate involuntary attentional allocation to such a stimulus. When an arrow cue indicated a to-be-ignored location that would never contain a target but would contain a colour singleton distractor, a significant singleton capture effect was eliminated on ignore trials regardless of the consistency of the singleton colour in Experiments 1 and 2. In Experiment 3, a consistent colour singleton was used without a spatial cue. Participants were not able to suppress singleton distractors in the absence of a cue. However, in Experiments 1 & 2, the status of a letter inscribed in the singleton (i.e., whether it is compatible or incompatible with the target of the search) did affect reaction time on ignore trials. If the compatibility effect indicates a shift of attention to the singleton, the data may mean that, with a spatial cue, participants inhibit a cued location by first selecting the location and then rapidly disengaging from it.

Search efficiency is not sufficient: The nature of search modulates stimulus-driven attention.

It has long been debated whether or not a salient stimulus automatically attracts people's attention in visual search. Recent findings showed that a salient stimulus is likely to capture attention especially when the search process was inefficient due to high levels of competition between the target and distractors. Expanding these studies, the present study proposes that a specific nature of visual search, as well as search efficiency, determines whether or not a salient, task-irrelevant singleton stimulus captures attention. To test this proposition, we conducted three experiments, in which participants performed two visual search tasks whose underlying mechanisms are known to be different: orientation-feature search and Landolt-C search tasks. We found that color singleton distractors captured attention when participants performed the orientation-feature search task. The magnitude of this capture effect increased as search efficiency decreased. On the contrary, the capture by singleton distractors was not observed under the Landolt-C search task. This differential pattern of capture effect was not due to differences in search efficiency across the search tasks; even when search efficiency was controlled for, stimulus-driven capture of attention by a salient distractor was found only under the feature search. Based on these results, the present study suggests that in addition to search efficiency, the nature of search strategy and the extent to which attentional control is strained play crucial roles in observing stimulus-driven attentional capture in visual search.

Probabilistic retro-cues do not determine state in visual working memory

The effective use of our capacity-limited visual working memory (VWM) requires mechanisms that govern how it represents information. Validly cueing an item in VWM after encoding, for instance, enhances memory performance for that item and biases its state in VWM, bringing its representation to an active state such that attentional selection is biased towards perceptually similar inputs. Critically, when the retro-cue is less than 100% valid (i.e., probabilistic rather than deterministic), the effect of the cue on memory performance varies. Here we investigated whether deterministic and probabilistic retro-cues also differ in their influence over item state in VWM. Participants encoded two colored squares, and a retro-cue indicated which item was most likely to be probed in a subsequent memory test. Across blocks, we manipulated cue validity to be deterministic (100% valid) or probabilistic (70% valid). On a subset of trials, no memory probe was presented and the trial ended with a visual search task in which a colored distractor -matching the cued memory item, the non-cued item, or neither - was presented. Predictably, in the deterministic condition, the presence of a singleton distractor matching the cued item reliably slowed reaction times during visual search. In the probabilistic condition, however, there were no differences in reaction times when the singleton matched the cued item or the non-cued item, despite a reliable benefit to memory performance on valid memory trials. We suggest that, while probabilistic retro-cues improve memory of the cued item, they are not sufficient to bias its state in VWM.

The Power of Negative Thinking: Paradoxical but Effective Ignoring of Salient-but-Irrelevant Stimuli by a Spatial Cue

It is often assumed that a uniquely colored singleton among other uniformly colored stimuli can function as a powerful attractor of attention (Theeuwes, 1992). However, top-down attentional mechanisms are also powerful and can suppress distractors when a pre-cue is given (Cunningham & Egeth, 2016; Munneke, Van der Stigchel, & Theeuwes, 2008). The current study tested whether an endogenous spatial cue indicating the location of a salient color singleton distractor can eliminate involuntary attentional allocation to such a stimulus. On each trial, either a capital "B" or "F" was randomly presented as the target letter. On ignore trials, an arrow cue indicated a to-be-ignored location that would never contain a target but would contain a color singleton distractor. Neutral trials provided no useful spatial information. Target-distractor compatibility was manipulated with a lowercase 'b' or 'f' distractor to test processing of the cued location. The results showed that a significant singleton capture effect was eliminated on ignore trials regardless of the consistency of the singleton color (Experiments 1 & 2). Significant compatibility effects were observed on both ignore and neutral trials, suggesting that participants adopted the strategy of selecting the cued location followed by rapid disengagement from that location on ignore trials. Overall, a spatial cue produces paradoxical but effective ignoring of salient-but-irrelevant stimuli; with a spatial cue, participants inhibited a cued location by first selecting the location and then rapidly disengaging from it. To explore whether participants could learn to ignore the color singleton in the absence of a spatial cue (Gaspelin & Luck, 2017; Vatterott & Vecera, 2012), in Experiment 3, only neutral trials were used with a consistent color singleton. Participants were not able to suppress singleton distractors, although the magnitude of singleton capture effects was reduced compared to that of neutral trials in Experiments 1 and 2. Meeting abstract presented at VSS 2018

No suppression of stimulus-driven capture with distractor and target singletons of the same (color) dimension

No suppression of stimulus-driven capture with distractor and target singletons of the same (color) dimension

Statistical learning shapes distractor suppression

Even though traditionally attentional control is considered to be the result of the interaction between top-down and bottom-up mechanisms, Awh, Belopolsky and Theeuwes (2012, TICS) have suggested a theoretical framework in which this division is argued to be incomplete. They argued that the history of attentional deployments can elicit lingering selection biases, which are unrelated to top-down goals or the physical salience of items. Whereas previous work has primarily focused on target selection, here we investigated whether implicitly learned statistical regularities can influence distractor processing. We used the additional singleton task in which participants search for a salient shape singleton while ignoring a color distractor singleton. This color distractor was systematically presented more often in one location than in all other locations. Using measures of behavior, we demonstrate that for this high-probability location, both the amount of attentional capture by distractors and the efficiency of selecting the target were reduced. Measures of brain activity, specifically the Pd (distractor positivity) and N2pc components of the event-related potential, were used to track the allocation of attention and suppression to lateralized positions in the arrays. We find evidence for a Pd-like component for the high probability location, even though both the target and the distractor were presented on the vertical meridian (top and bottom) and thus could not themselves elicit a lateralized component in the ERP. When the distractor was presented at the lateralized high probability location, this also generated a Pd, while a distractor presented at a low probability location generated an N2pc. The same was found for when the target was presented at the high versus low lateralized probability location. We interpret these findings as evidence that spatial statistical regularities influence distractor processing through inhibition of high probability locations.

Statistical regularities modulate attentional capture independent of search strategy

An earlier study using the additional singleton task showed that statistical regularities regarding the distractor location can cause an attentional bias that affects the amount of attentional capture by distractors and the efficiency of selection of targets. The distractor singleton was systematically present more often in one location than in all other locations. The present study investigated whether this bias also occurs when observers adopt a feature search mode, i.e., when they search for a specific feature (circle) between elements with different shapes, while ignoring a colored distractor singleton. It is assumed that in feature search, observers can ignore distractors in a top-down way and as such one expects that statistical regularities about the distractor location should not play a role. Contrary to this prediction, we found that even in feature search, both attentional capture by the distractors and the efficiency of selecting the target were impacted by these statistical regularities. Moreover, statistical regularities regarding the feature value of the distractor (its color) had no effect on the amount of capture or the efficiency of selection. We claim that statistical regularities cause passive lingering biases of attention such that on the priority map, the location containing a high probability distractor competes less for attention than locations that are less likely to contain distractors.

Attentional selection and suppression in children and adults.

The fundamental role of covert spatial attention is to enhance the processing of attended items while simultaneously ignoring irrelevant items. However, relatively little is known about how brain electrophysiological activities associated with target selection and distractor suppression are involved as they develop and become fully functional. The current study aimed to identify the neurophysiological bases of the development of covert spatial attention, focusing on electroencephalographic (EEG) markers of attentional selection (N2pc) and suppression (PD ). EEG data were collected from healthy young adults and typically developing children (9-15 years old) as they searched for a shape singleton target in either the absence or the presence of a salient-but-irrelevant color singleton distractor. The ERP results showed that a lateral shape target elicited a smaller N2pc in children compared with adults regardless of whether a distractor was present or not. Moreover, the target-elicited N2pc was always followed by a similar positivity in both age groups. Counterintuitively, a lateral salient-but-irrelevant distractor elicited a large PD in children with low behavioral accuracy, whereas high-accuracy children exhibited a small and "adult-like" PD . More importantly, we found no evidence for a correlation between the target-elicited N2pc and the distractor-elicited PD in either age group. Our results provide neurophysiological evidence for the developmental differences between target selection and distractor suppression. Compared with adults, 9-15-year-old children deploy insufficient attentional selection resources to targets but use "adult-like" or even more attentional suppression resources to resist irrelevant distractors. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=NhWapx0d75I.

How to inhibit a distractor location? Statistical learning versus active, top-down suppression.

Recently, Wang and Theeuwes (Journal of Experimental Psychology: Human Perception and Performance, 44(1), 13-17, 2018a) demonstrated the role of lingering selection biases in an additional singleton search task in which the distractor singleton appeared much more often in one location than in all other locations. For this location, there was less capture and selection efficiency was reduced. It was argued that statistical learning induces plasticity within the spatial priority map such that particular locations that are high likely to contain a distractor are suppressed relative to all other locations. The current study replicated these findings regarding statistical learning (Experiment 1) and investigated whether similar effects can be obtained by cueing the distractor location in a top-down way on a trial-by-trial basis. The results show that top-down cueing of the distractor location with long (1,500 ms; Experiment 2) and short stimulus-onset symmetries (SOAs) (600 ms; Experiment 3) does not result in suppression: The amount of capture nor the efficiency of selection was affected by the cue. If anything, we found an attentional benefit (instead of the suppression) for the short SOA. We argue that through statistical learning, weights within the attentional priority map are changed such that one location containing a salient distractor is suppressed relative to all other locations. Our cueing experiments show that this effect cannot be accomplished by active, top-down suppression. Consequences for recent theories of distractor suppression are discussed.

Statistical regularities modulate attentional capture.

The present study investigated whether statistical regularities can influence visual selection. We used the classic additional singleton task in which participants search for a salient shape singleton while ignoring a color distractor singleton. The color distractor singleton was systematically presented more often in 1 location than in all other locations. For this high-probability location, we found that both the amount of attentional capture by distractors and the efficiency of selecting the target were reduced. There was a spatial gradient of suppression, as the attentional capture effect and the efficiency of selecting the target scaled with the distance from the high-probability location. Some participants were aware of the statistical regularities, but this did not affect the results whatsoever. We interpret these findings as evidence that spatially statistical regularities that are unknown to the observer can influence attention such that locations that have a high probability of containing a distractor are suppressed relative to all other locations. (PsycINFO Database Record

Attentional Capture to a Singleton Distractor Degrades Visual Marking in Visual Search.

Visual search is easier after observing some distractors in advance; it is as if the previewed distractors were excluded from the search. This effect is referred to as the preview benefit, and a memory template that visually marks the old locations of the distractors is thought to help in prioritizing the locations of newly presented items. One remaining question is whether the presence of a conspicuous item during the sequential shift of attention within the new items reduces this preview benefit. To address this issue, we combined the above preview search and a conventional visual search paradigm using a singleton distractor and examined whether the search performance was affected by the presence of the singleton. The results showed that the slope of reaction time as a function of set size became steeper in the presence of a singleton, indicating that the singleton distractor reduced the preview benefit. Furthermore, this degradation effect was positively correlated with the degree of conventional attentional capture to a singleton measured in a separate experiment with simultaneous search. These findings suggest that the mechanism of visual marking shares common attentional resources with the search process.