Color Singleton Distractor Research Articles

Classic Visual Search Effects in an Additional Singleton Task: An Open Dataset.

Visual search refers to our ability to find what we are looking for among many competing visual inputs. Here, we report the availability of a rich dataset that replicates key visual search effects and shows that these effects are robust to several changes to the experimental design. Experiment 1 replicates classic findings from an additional singleton visual search task. First, participants are captured by a salient but irrelevant color singleton, as indexed by slower response times when a color singleton distractor is present versus absent. Second, attentional capture by a color singleton is reduced when the visual search array contains heterogeneous shapes rather than homogenous shapes. Finally, attentional capture by a color singleton is reduced when the display colors are repeated rather than switched unpredictably from trial to trial. Experiment 2 demonstrates that these classic visual search effects are robust to small procedural changes such as task timing (i.e., a 2–8 second rather than ~1 second inter-trial interval). Experiment 3 demonstrates that these classic effects are likewise robust to changes to the distractor frequency (75% rather than 50%) and to fully blocking versus interleaving blocks of two task conditions. All told, this dataset includes 8 sub-experiments, 190 participants and >210,000 trials, and it will serve as a useful resource for power analyses and exploratory analyses of visual search behaviors.

PD components and distractor inhibition in visual search: New evidence for the signal suppression hypothesis.

The hypothesis that salient distractors in visual search are actively suppressed is supported by the fact that these objects elicit PD components believed to be associated with inhibition. This account was challenged by researchers who found that a PD to lateral color singleton distractors was followed by a contralateral negativity, which they interpreted as an N2pc indicative of attentional capture. As this would be at odds with successful distractor suppression, they proposed an alternative lateral-first serial scanning hypothesis, which assumes that the PD might actually be an N2pc elicited when a lateral context item is selected. We tested this hypothesis by measuring lateralized ERP components to search displays with two lateral and two vertical midline items, including a color singleton and a shape-defined target. Color singletons triggered PD components not only in blocks where attention was unfocused because target location was unpredictable, but critically also in blocks where targets only appeared on the midline and participants had no reason to attend to lateral items. This is inconsistent with the serial scanning hypothesis and supports the idea that the PD reflects signal suppression. PD components to singleton distractors were followed by a contralateral negativity, which we interpreted as a second PD elicited by nonsalient distractors on the opposite side. Our sequential inhibition account reconciles conflicting results of recent studies and emphasizes the role of inhibitory processes during attentional target selection in visual search.

Reduction of temporal uncertainty facilitates stimulus-driven processes in spatial selection

Previous studies have shown that the reduction of temporal uncertainty facilitates target selection in visual search. We investigated whether this beneficial effect is caused by an effect on stimulus-driven processes or on goal-driven processes in spatial selection. To discriminate between these processes, we employed a visual search task in which participants searched for a shape target while ignoring a color singleton distractor. As an index of stimulus-driven processes, we measured the N2pc evoked by the singleton distractor (ND). As indices of goal-driven processes, we measured the N2pc evoked by the target (NT) and the distractor positivity (PD) evoked by the singleton distractor, respectively. We observed that reducing temporal uncertainty modulated the amplitude of ND and the onset latency of the NT, but did not modulate the amplitude of the PD. These results are consistent with the view that a reduction of temporal uncertainty influences non-selective, stimulus-driven processes in spatial selection.

Context isn't everything: Search performance is influenced by the nature of the task but not the background.

AbstractIt has been demonstrated in the literature that cues in the environment that are predictive of how a task ought to be performed can influence performance. In an extension of this general notion, Cosman and Vecera (Journal of Experimental Psychology: Human Perception and Performance, 39(3), 836-848, 2013) reported that simply performing singleton and feature search tasks when irrelevant scenes were displayed in the background automatically modulated the search strategies adopted by participants when these scenes were reinstated at a later time. While intriguing, this result was also somewhat surprising given that an adaptive system (like the human brain) should disregard irrelevant information so task competencies generalize across environments. To investigate this issue further, we replicated the experimental procedures of Cosman and Vecera, while varying whether the test phase was either a singleton search (Experiments 1 and 3) or a feature search (Experiment 2) task. While it was observed that the nature of the search task varied whether a color singleton distractor influenced performance, there was no evidence that background scenes modulated the search strategies adopted by participants, contrasting the results of Cosman and Vecera. Overall, the findings here support the conclusion that the visual system prioritizes task-relevant information while disregarding irrelevant background information.

Impacts of Relative and Absolute Values on Selective Attention

Valuable stimuli receive attentional priority. However, it is unknown whether the mechanism of the attentional priority is based on relative (e.g., higher or lower than the value of another available object) or absolute value (e.g., 45 points) because high valued stimuli were relatively and absolutely valuable more than low valued stimuli in previous research. To investigate the impacts of the relative and absolute values on selective attention, we manipulated the relative and absolute values independently in a modified value-driven attention capture paradigm. In the training phase, reward was presented during a visual search task to aid associative learning between color and reward value, two test target colors were each presented with another different target color (reference target colors) in separate context blocks. Therefore, each test target color had different reference points. In the test phase, the two test target colors were presented as singleton distractor colors during a shape singleton search task. In Experiment 1, the absolute value of the reward associated with the two test target colors was the same, but one had a relatively higher value compared to its reference target color and the other had a relatively lower value. The relatively higher-valued color singleton distractor captured attention more than the relatively lower in test phase, suggesting that the relative value of stimuli influenced selective attention. In Experiment 2 the relative value of the test target colors was the same, but the absolute value was higher for one. The higher and lower absolute valued color singleton distractors captured attention equally, indicating little impact of the absolute value on attention. The present study suggests that the relative rather than absolute value plays a critical role in attention allocation, and that prospect theory (Kahneman & Tversky, 1979) may extend to earlier cognitive stages such as selective attention.

Independent effects of statistical learning and top-down attention

It is well known that spatial attention can be directed in a top-down way to task-relevant locations in space. In addition, through visual statistical learning (VSL), attention can be biased towards relevant (target) locations and away from irrelevant (distractor) locations. The present study investigates the interaction between the explicit task-relevant, top-down attention and the lingering attentional biases due to VSL. We wanted to determine the contribution of each of these two processes to attentional selection. In the current study, participants performed a search task while keeping a location in spatial working memory. In Experiment 1, the target appeared more often in one location, and appeared less often in other location. In Experiment 2, a color singleton distractor was presented more often in location than in all other locations. The results show that when the search target matched the location that was kept in working memory, participants were much faster at responding to the search target than when it did not match, signifying top-down attentional selection. Independent of this top-down effect, we found a clear effect of VSL as responses were even faster when target (Experiment 1) or the distractor (Experiment 2) was presented at a more likely location in visual field. We conclude that attentional selection is driven by implicit biases due to statistical learning and by explicit top-down processing, each process individually and independently modulating the neural activity within the spatial priority map.

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).

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).

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.

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

Bottom-up attention capture with distractor and target singletons defined in the same (color) dimension is not a matter of feature uncertainty

In visual search, attention capture by an irrelevant color-singleton distractor in another feature dimension than the target is dependent on whether or not the distractor changes its feature: Capture is present if the irrelevant color distractor can take on different features across trials, but absent if the distractor takes on only one feature throughout all trials. This influence could be due to down-weighting of the entire color map. Here we tested whether a similar effect could also be brought about by down-weighting of specific color channels within the same maps. We investigated whether a similar dependence of capture on color certainty might hold true if the distractor were defined in the same (color) dimension as the target. At odds with this possibility, in the first and third blocks—in which feature uncertainty was absent—an irrelevant distractor of a certain color captured attention. In addition, in a second block, varying the distractor color created feature uncertainty, but this did not increase capture. Repeating the exact same procedure with the same participants after one week confirmed the stability of the results. The present study showed that a color distractor presented in the same (color) dimension as the target captures attention independent of feature uncertainty. Thus, the down-weighting of single irrelevant color channels within the same feature map used for target search is not a matter of feature uncertainty.

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.

Rejecting salient distractors: Generalization from experience.

Distraction impairs performance of many important, everyday tasks. Attentional control limits distraction by preferentially selecting important items for limited-capacity cognitive operations. Research in attentional control has typically investigated the degree to which selection of items is stimulus-driven versus goal-driven. Recent work finds that when observers initially learn a task, the selection is based on stimulus-driven factors, but through experience, goal-driven factors have an increasing influence. The modulation of selection by goals has been studied within the paradigm of learned distractor rejection, in which experience over a sequence of trials enables individuals eventually to ignore a perceptually salient distractor. The experiments presented examine whether observers can generalize learned distractor rejection to novel distractors. Observers searched for a target and ignored a salient color-singleton distractor that appeared in half of the trials. In Experiment 1, observers who learned distractor rejection in a variable environment rejected a novel distractor more effectively than observers who learned distractor rejection in a less variable, homogeneous environment, demonstrating that variable, heterogeneous stimulus environments encourage generalizable learned distractor rejection. Experiments 2 and 3 investigated the time course of learned distractor rejection across the experiment and found that after experiencing four color-singleton distractors in different blocks, observers could effectively reject subsequent novel color-singleton distractors. These results suggest that the optimization of attentional control to the task environment can be interpreted as a form of learning, demonstrating experience's critical role in attentional control.

Towards a resolution of the attentional-capture debate.

The relative contributions of stimulus-driven and goal-directed control of attention have been extensively studied by investigating which irrelevant stimuli capture attention. Although much of this research has focused on color-singleton distractors, the circumstances under which these capture attention remain controversial. In search for a target with a unique known color (known-singleton search), whether singletons in an irrelevant color can be successfully ignored is a hotly debated issue. In search for a target that is not a singleton (feature search), no capture by irrelevant-color singletons is typically observed, but a reverse cueing effect was occasionally reported in the spatial-cueing paradigm. In 3 experiments, we resolve these controversies, by showing that the net spatial effect observed in the spatial-cueing paradigm reflects the sum of 3 separate effects. (a) A same-location benefit, which is determined by the match between the cue and the target colors and indexes contingent attentional capture. (b) A same-location cost, which is also determined by the match between the cue and the target colors, but occurs after selection and indexes processes related to visual working memory; and (c) task-dependent capture by singletons that occurs only when the target is consistently a singleton. Crucially, we show that the same-location cost is strongly determined by cue exposure duration, which explains previous failures to isolate it. The implications of these findings for the attentional capture debate are discussed.

The Role of Conscious Perception in Attentional Capture and Object-File Updating

A mental process that is independent of conscious perception should run equally well with or without it. Previous investigations of unconscious processing have seldom included this comparison: They typically demonstrated only processing without conscious perception. In the research reported here, we showed that attentional capture is largely independent of conscious perception and that updating the episodic information stored about an object is entirely contingent on conscious perception. We used a spatial-cuing paradigm, in which the cue was a color-singleton distractor rendered liminal by continuous flash suppression or brief exposure. When the cue matched the participant’s attentional set, it strongly captured attention whether it was subliminal or consciously perceived. In contrast, a nonmatching cue did not capture attention but instead produced a same-location cost, which was contingent on consciously perceiving the cue. Our findings demonstrate a dissociation between attention and conscious perception and unveil an important boundary condition of object-file updating.

Age mediation of frontoparietal activation during visual feature search

Activation of frontal and parietal brain regions is associated with attentional control during visual search. We used fMRI to characterize age-related differences in frontoparietal activation in a highly efficient feature search task, detection of a shape singleton. On half of the trials, a salient distractor (a color singleton) was present in the display. The hypothesis was that frontoparietal activation mediated the relation between age and attentional capture by the salient distractor. Participants were healthy, community-dwelling individuals, 21 younger adults (19–29years of age) and 21 older adults (60–87years of age). Top-down attention, in the form of target predictability, was associated with an improvement in search performance that was comparable for younger and older adults. The increase in search reaction time (RT) associated with the salient distractor (attentional capture), standardized to correct for generalized age-related slowing, was greater for older adults than for younger adults. On trials with a color singleton distractor, search RT increased as a function of increasing activation in frontal regions, for both age groups combined, suggesting increased task difficulty. Mediational analyses disconfirmed the hypothesized model, in which frontal activation mediated the age-related increase in attentional capture, but supported an alternative model in which age was a mediator of the relation between frontal activation and capture.

Functional brain connectivity and cognition: effects of adult age and task demands

Previous neuroimaging research has documented that patterns of intrinsic (resting state) functional connectivity (FC) among brain regions covary with individual measures of cognitive performance. Here, we examined the relation between intrinsic FC and a reaction time (RT) measure of performance, as a function of age group and task demands. We obtained filtered, event-related functional magnetic resonance imaging data, and RT measures of visual search performance, from 21 younger adults (19–29 years old) and 21 healthy, older adults (60–87 years old). Age-related decline occurred in the connectivity strength in multiple brain regions, consistent with previous findings. Among 8 pairs of regions, across somatomotor, orbitofrontal, and subcortical networks, increasing FC was associated with faster responding (lower RT). Relative to younger adults, older adults exhibited a lower strength of this RT-connectivity relation and greater disruption of this relation by a salient but irrelevant display item (color singleton distractor). Age-related differences in the covariation of intrinsic FC and cognitive performance vary as a function of task demands.

Attentional Capture by Salient Distractors during Visual Search Is Determined by Temporal Task Demands

The question whether attentional capture by salient but task-irrelevant visual stimuli is triggered in a bottom-up fashion or depends on top-down task settings is still unresolved. Strong support for bottom-up capture was obtained in the additional singleton task, in which search arrays were visible until response onset. Equally strong evidence for top-down control of attentional capture was obtained in spatial cueing experiments in which display durations were very brief. To demonstrate the critical role of temporal task demands on salience-driven attentional capture, we measured ERP indicators of capture by task-irrelevant color singletons in search arrays that could also contain a shape target. In Experiment 1, all displays were visible until response onset. In Experiment 2, display duration was limited to 200 msec. With long display durations, color singleton distractors elicited an N2pc component that was followed by a late Pd component, suggesting that they triggered attentional capture, which was later replaced by location-specific inhibition. When search arrays were visible for only 200 msec, the distractor-elicited N2pc was eliminated and was replaced by a Pd component in the same time range, indicative of rapid suppression of capture. Results show that attentional capture by salient distractors can be inhibited for short-duration search displays, in which it would interfere with target processing. They demonstrate that salience-driven capture is not a purely bottom-up phenomenon but is subject to top-down control.

Trial-by-trial adjustments of top-down set modulate oculomotor capture

The role of top-down control in visual search has been a subject of much debate. Recent research has focused on whether attentional and oculomotor capture by irrelevant salient distractors can be modulated through top-down control, and if so, whether top-down control can be rapidly initiated based on current task goals. In the present study, participants searched for a unique shape in an array containing otherwise homogeneous shapes. A cue prior to each trial indicated the probability that an irrelevant color singleton distractor would appear on that trial. Initial saccades were less likely to land on the target and participants took longer to initiate a saccade to the target when a color distractor was present than when it was absent; this cost was greatly reduced on trials in which the probability that a distractor would appear was high, as compared to when the probability was low. These results suggest that top-down control can modulate oculomotor capture in visual search, even in a singleton search task in which distractors are known to readily capture both attention and the eyes. Furthermore, the results show that top-down distractor suppression mechanisms can be initiated quickly in anticipation of irrelevant salient distractors and can be adjusted on a trial-by-trial basis.

The visual hemifield asymmetry in the spatial blink during singleton search and feature search

The present study examined a visual field asymmetry in the contingent capture of attention that was previously observed by Du and Abrams (2010). In our first experiment, color singleton distractors that matched the color of a to-be-detected target produced a stronger capture of attention when they appeared in the left visual hemifield than in the right visual hemifield. This replicated Du and Abrams and also revealed a difference between hemifields in the time course of this effect. Our second experiment suggested that this asymmetry is moderated by the tuning of attentional control settings: when the target was easier to detect the asymmetry was attenuated. Our third experiment showed that this asymmetry is also present during singleton detection: a color singleton distractor produced a larger capture effect in the left hemifield than in the right hemifield. Finally, our fourth experiment suggested that this asymmetry is moderated by the salience of the attention-capturing distractor: when the distractor was not salient, the asymmetry was attenuated. These results suggest that there are boundary conditions in the observed hemifield asymmetry in the contingent capture of attention and several underlying brain systems might be involved.