Singleton Search Research Articles

Target templates and the time course of distractor location learning

When searching for a shape target, colour distractors typically capture our attention. Capture is smaller when observers search for a fixed target that allows for a feature-specific target template compared to a varying shape singleton target. Capture is also reduced when observers learn to predict the likely distractor location. We investigated how the precision of the target template modulates distractor location learning in an additional singleton search task. As observers are less prone to capture with a feature-specific target, we assumed that distractor location learning is less beneficial and therefore less pronounced than with a mixed-feature target. Hierarchical Bayesian parameter estimation was used to fit fine-grained distractor location learning curves. A model-based analysis of the time course of distractor location learning revealed an effect on the asymptotic performance level: when searching for a fixed-feature target, the asymptotic distractor cost indicated smaller distractor interference than with a mixed-feature target. Although interference was reduced for distractors at the high-probability location in both tasks, asymptotic distractor suppression was less pronounced with fixed-feature compared to mixed-feature targets. We conclude that with a more precise target template less distractor location learning is required, likely because the distractor dimension is down-weighted and its salience signal reduced.

Will to the Original: Platonism in Henry James’ Roderick Hudson

Will to the Original: Platonism in Henry James’ <i>Roderick Hudson</i>

Preparatory template activation during feature versus singleton search

Preparatory template activation during feature versus singleton search

Search mode, not the attentional window, determines the magnitude of attentional capture

A salient color distractor is known to capture attention during search for a less salient shape target, but the mechanisms underlying attentional capture are debated. Theeuwes (2004, Psychonomic Bulletin & Review, 11(1), 65–70) argued that attentional capture depends on the size of the attentional window. If the attentional window is large, search is efficient and attentional capture should be stronger because the distractor is more likely to be inside the window. Consistently, we found higher search efficiency and more attentional capture in singleton than in feature search. However, differences in attentional capture only occurred when singleton and feature search were performed by different groups of participants, but not when singleton and feature search occurred unpredictably in the same group of participants. This result contradicts the attentional window account because search efficiency was always higher in singleton than in feature search. Rather, the results support search mode theory, which claims that participants looked for the most salient stimulus in singleton search (“singleton detection mode”), which resulted in more capture by the salient color distractor. When search types varied unpredictably, it was impossible to apply a consistent search strategy, which eliminated the differences between singleton and feature search. Further, we manipulated search efficiency by target–nontarget similarity. With dissimilar nontargets, the target was salient and search efficiency was high. Therefore, the attentional window account predicts more capture. However, we found the opposite result in singleton search and no difference in feature search. Taken together, these observations are inconsistent with the attentional window account but support search mode theory.

Top-down then automatic: Instructions can continue to influence visual search when no longer actively implemented.

The present study investigated the automaticity of top-down instructions in visual search when the instruction was no longer actively implemented. To do so, we exploited the Priming of Pop-out (PoP) effect, a selection history phenomenon that reflects faster responses when the target and distractor colors are repeated than switched across trials of singleton search. We then had participants perform a color singleton search task where they implemented the instruction of imagining the opposite color of the previous target, which put the target colors underlying PoP and the imagery instruction in opposition. To assess automaticity, on some trials participants were instructed to stop implementing the imagery instruction. When the imagery instruction was implemented, responses were faster when the target and distractor colors switched (i.e., imagery congruent) than repeated (i.e., imagery incongruent) across search displays - a pattern of results opposite to the PoP effect. When participants were to not implement this instruction, the PoP effect was absent, indicating the imagery instruction had a lingering influence on visual search. This remained true even when participants reported successfully not implementing the instruction, and only when the imagery abandonment instruction was supplanted by a different top-down task was the lingering influence removed such that the PoP effect returned. Overall, the present study demonstrates that top-down instructions can continue to influence visual search despite the will of the observer.

Selection history and task predictability determine the precision expectations in attentional control.

Predictive processing frameworks have demonstrated the central role that prediction plays in a range of cognitive processes including bottom-up and top-down mechanisms of attention control. However, relatively little is understood about how predictive processes interact with the third main determinant of attentional priority - selection history. In this experiment, participants developed a history of either color or shape selection while we observed the impact of these histories in an additional singleton search task using behavioral measures and ERP measures of attentional control. Throughout the experiment, participants were encouraged to predict the upcoming display, but prediction errors were either high or low depending on session. Persistent group differences in our results showed that selection history contributes to the precision weighting of a stimulus, and that this is mediated by overall prediction error. Color-singleton distractors captured attention and required greater suppression when participants had a history of color selection; however, these participants gained large benefits when the upcoming stimuli were highly predictable. We suggest that selection history modulates the precision expectations for a feature in a persistent and implicit way, producing an attentional bias that predictability can help to counteract, but cannot prevent or eliminate entirely.

On target selection as reflected by posterior ERP components in feature-guided visual search.

The N2pc event-related potential is a widely studied ERP component that reflects the covert deployment of visuo-spatial attention to target stimuli displayed laterally relative to fixation. Recently, an analogous ERP component, named N2pcb, has been proposed as a marker of the deployment of visuo-spatial attention to targets displayed on the vertical midline. Two studies that investigated the N2pcb component found analogous results, using however two different algorithms to compute the amplitude of N2pcb. One study subtracted the ipsilateral activity elicited by a lateral target from the bilateral activity elicited by a target displayed on the vertical midline, whereas the other study subtracted the bilateral activity elicited by target-absent displays from the bilateral activity elicited by a target displayed on the vertical midline. Here we show both algorithms estimate properly the N2pc as well as the N2pcb components. In addition, we explored whether the singleton detection positivity (SDP) component, a posterior bilateral positivity temporally concomitant to N2pc recently reported in studies using singleton search, could be observed in the present study in which a target was defined by a combination of features. Given that such component was indeed found using feature search, we named this component posterior processing positivity (PPP), and showed that bilateral activity elicited by target-absent displays is an adequate baseline for its correct isolation.

Guidance of visual search by negative attentional templates depends on task demands.

Visual search for a target is faster when its features are known before the search display appears, but there is an ongoing discussion about whether knowledge of nontarget features has a similar effect. Stored target or nontarget features used to guide visual search are referred to as positive or negative attentional templates, respectively. We suggest that the inconsistent findings concerning negative attentional templates may arise from 2 methodological choices in past research. The activation of negative attentional templates was never directly assessed and the use of negative attentional templates by the participant was optional. We addressed these issues in the contingent capture paradigm, which provides a marker for the activation of attentional templates in conditions where attentional templates are optional or mandatory. If an attentional template for a color is activated, cuing effects are larger for spatial cues in a matching color than for spatial cues in a nonmatching color. The question is whether the activation of negative attentional templates results in a similar difference between matching and nonmatching colors. We found that negative attentional templates were not activated when the target could be located based on its saliency (singleton search) and the use of the negative attentional template was optional. In contrast, when the negative attentional template was necessary to locate the target (feature search), we found the expected difference between matching and nonmatching spatial cues. Thus, the activation of negative attentional templates depends on task demands. In contrast, positive attentional templates were activated irrespective of task demands. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Pop-out search instigates beta-gated feature selectivity enhancement across V4 layers

Visual search is a workhorse for investigating how attention interacts with processing of sensory information. Attentional selection has been linked to altered cortical sensory responses and feature preferences (i.e., tuning). However, attentional modulation of feature selectivity during search is largely unexplored. Here we map the spatiotemporal profile of feature selectivity during singleton search. Monkeys performed a search where a pop-out feature determined the target of attention. We recorded laminar neural responses from visual area V4. We first identified "feature columns" which showed preference for individual colors. In the unattended condition, feature columns were significantly more selective in superficial relative to middle and deep layers. Attending a stimulus increased selectivity in all layers but not equally. Feature selectivity increased most in the deep layers, leading to higher selectivity in extragranular layers as compared to the middle layer. This attention-induced enhancement was rhythmically gated in phase with the beta-band local field potential. Beta power dominated both extragranular laminar compartments, but current source density analysis pointed to an origin in superficial layers, specifically. While beta-band power was present regardless of attentional state, feature selectivity was only gated by beta in the attended condition. Neither the beta oscillation nor its gating of feature selectivity varied with microsaccade production. Importantly, beta modulation of neural activity predicted response times, suggesting a direct link between attentional gating and behavioral output. Together, these findings suggest beta-range synaptic activation in V4's superficial layers rhythmically gates attentional enhancement of feature tuning in a way that affects the speed of attentional selection.

Attentional templates are sharpened through differential signal enhancement, not differential allocation of attention

In visual search, the internal representation of the target feature is referred to as the attentional template. The attentional template can be broad or precise depending on the task requirements. In singleton search, the attentional template is broad because the target is the only colored element in the display. In feature search, a precise attentional template is required because the target is in a specific color in an array of varied colors. To measure the precision of the attentional template, we used a cue-target paradigm where cueing benefits decrease when the cue color differs from the target color. Consistent with broad and precise attentional templates, the decrease of cueing effects was stronger in feature than in singleton search. Measurements of ERPs showed that the N2pc elicited by the cue decreased with increasing color difference, suggesting that attention was more strongly captured by cues that were similar to the target. However, the cue-elicited N2pc did not differ between feature and singleton search, making it unlikely to reflect the mechanism underlying attentional template precision. Furthermore, there was no evidence for attentional suppression as there was no cue-elicited PD, even in conditions where the cueing benefit turned into a same-location cost. However, an index of signal enhancement, the contralateral positivity, reflected attention template precision. In general, there was sensory enhancement of the stimulus appearing at the cued location in the search display. With broad attentional templates, any stimulus at the cued location was enhanced, whereas enhancement was restricted to target-matching colors with precise attentional templates.

Attentional capture in goal-directed action during childhood, adolescence, and early adulthood

Attentional capture occurs when salient but task-irrelevant information disrupts our ability to respond to task-relevant information. Although attentional capture costs have been found to decrease between childhood and adulthood, it is currently unclear the extent to which such age-related changes reflect an improved ability to recover from attentional capture or to avoid attentional capture. In addition, recent research using hand-tracking techniques with adults indicates that attentional capture by a distractor can generate response activations corresponding to the distractor’s location, consistent with action-centered models of attention. However, it is unknown whether attentional capture can also result in the capture of action in children and adolescents. Therefore, we presented 5-year-olds, 9-year-olds, 13- and 14-year-olds, and adults (N = 96) with a singleton search task in which participants responded by reaching to touch targets on a digital display. Consistent with action-centered models of attention, distractor effects were evident in each age group’s movement trajectories. In contrast to movement trajectories, movement times revealed significant age-related reductions in the costs of attentional capture, suggesting that age-related improvements in attentional control may be driven in part by an enhanced ability to recover from—as opposed to avoid—attentional capture. Children’s performance was also significantly affected by response repetition effects, indicating that children may be more susceptible to interference from a wider range of task-irrelevant factors than adults. In addition to presenting novel insights into the development of attention and action, these results highlight the benefits of incorporating hand-tracking techniques into developmental research.

Comparing imagery and perception: Using eye movements to dissociate mechanisms in search.

It has been demonstrated that color imagery can have a profound impact when generated prior to search, while at the same time, perceptual cues have a somewhat limited influence. Given this discrepancy, the present study evaluated the processes impacted by imagery and perception using a singleton search task where participants had to find an oddball colored target among homogenously colored distractors. Prior to each trial, a perceptual color was displayed or imagery was generated that could match the target, distractors, or neither item in the search array. It was revealed that color imagery led to both a larger benefit when it matched the target and a larger cost when it matched the distractors relative to perceptual cues. By parsing response times into pre-search, search, and response phases based on eye movements, it was revealed that, while imagery and perceptual cues both influenced the search phase, imagery had a significantly greater influencethan perceptual cues. Further, imagery influenced pre-search and response phases as well. Overall, the present findings reveal that the influence of imagery is profound as it affects multiple processes in the vision-perception pipeline, while perception only appeared to impact search.

Top-down imagery overrides the influence of selection history effects

The present study investigated whether color imagery could override the representations of the prevalent selection history effect termed Priming of Pop-out (PoP), which is constituted by faster responding when the target color is repeated rather than switched across trials of color singleton search. Participants imagined a color in the interval between trials of a color singleton search task that could be the same as or different to the previous target color, and they were to rate the vividness of these representations following each imagery event. It was revealed that when highly vivid imagery was reported, the PoP effect was attenuated relative to less vivid forms of it (and absent in two out of three experiments), and that color imagery eliminated the build-up of priming following consecutive target color repeats. Overall, the present findings suggest the representations of the selection history system can be overridden by top-down imagery.

Visual search under physical effort is faster but more vulnerable to distractor interference

Cognition and action are often intertwined in everyday life. It is thus pivotal to understand how cognitive processes operate with concurrent actions. The present study aims to assess how simple physical effort operationalized as isometric muscle contractions affects visual attention and inhibitory control. In a dual-task paradigm, participants performed a singleton search task and a handgrip task concurrently. In the search task, the target was a shape singleton among distractors with a homogeneous but different shape. A salient-but-irrelevant distractor with a unique color (i.e., color singleton) appeared on half of the trials (Singleton distractor present condition), and its presence often captures spatial attention. Critically, the visual search task was performed by the participants with concurrent hand grip exertion, at 5% or 40% of their maximum strength (low vs. high physical load), on a hand dynamometer. We found that visual search under physical effort is faster, but more vulnerable to distractor interference, potentially due to arousal and reduced inhibitory control, respectively. The two effects further manifest in different aspects of RT distributions that can be captured by different components of the ex-Gaussian model using hierarchical Bayesian method. Together, these results provide behavioral evidence and a novel model for two dissociable cognitive mechanisms underlying the effects of simple muscle exertion on the ongoing visual search process on a moment-by-moment basis.

Automatic capture of attention by flicker

Visual motion captures attention, but little is known about the automaticity of these effects. Here, we tested if deviant flicker frequencies, as one form of motion, automatically capture attention. Observers searched for a vertical target among tilted distractors. Prior to the target display, a cue array of sinusoidally modulating (flickering) annuli, each surrounding one location of the subsequent target(-plus-distractors) display was presented for variable durations. Annuli either flickered all at 1 Hz (neutral condition, no-singleton cue), or a single annulus flickered at a unique frequency of 5 Hz, 10 Hz, or 15 Hz. The location of this singleton-frequency cue was uncorrelated with target location. Thus, we could measure benefits (target at cued location) and costs (target ≠ cued location) for cues of different frequencies and durations. The results showed that deviant flicker frequencies capture attention, as we observed benefits and costs, falsifying that nonspatial filtering accounted for the cueing effect. In line with automatic capture, cueing was effective in singleton (Experiment 1) and nonsingleton search tasks (Experiment 2), and is thus not dependent on (“top-down”) singleton detection mode. Moreover, analysis of results ruled out trial-by-trial “swapping” of flicker frequencies from preceding target to subsequent distractor locations. Results also revealed increasing cueing effects with higher cue flicker frequency and longer duration. This indicates a significantly longer period of automatic capture by sinusoidal flicker than the typical inhibition of return observed around 250 ms after the onset of uninformative static or single-transient cues.

Attentional Templates Are Sharpened through Differential Signal Enhancement, Not Differential Allocation of Attention.

In visual search, the internal representation of the target feature is referred to as the attentional template. The attentional template can be broad or precise depending on the task requirements. In singleton search, the attentional template is broad because the target is the only colored element in the display. In feature search, a precise attentional template is required because the target is in a specific color in an array of varied colors. To measure the precision of the attentional template, we used a cue-target paradigm where cueing benefits decrease when the cue color differs from the target color. Consistent with broad and precise attentional templates, the decrease of cueing effects was stronger in feature than in singleton search. Measurements of ERPs showed that the N2pc elicited by the cue decreased with increasing color difference, suggesting that attention was more strongly captured by cues that were similar to the target. However, the cue-elicited N2pc did not differ between feature and singleton search, making it unlikely to reflect the mechanism underlying attentional template precision. Furthermore, there was no evidence for attentional suppression as there was no cue-elicited PD, even in conditions where the cueing benefit turned into a same-location cost. However, an index of signal enhancement, the contralateral positivity, reflected attention template precision. In general, there was sensory enhancement of the stimulus appearing at the cued location in the search display. With broad attentional templates, any stimulus at the cued location was enhanced, whereas enhancement was restricted to target-matching colors with precise attentional templates.

Rapid disengagement hypothesis and signal suppression hypothesis of visual attentional capture

<p id="C3">In the traditional theory of visual attentional capture, the stimulus-driven theory and goal-driven theory were argued for nearly 20 years. Later, two new hybrid models were proposed, which combined bottom-up capture and top-down control settings, called the rapid disengagement hypothesis and the signal suppression hypothesis. The main content of the rapid disengagement hypothesis is that a salient distractor can always capture attention in a bottom-up manner, but attention is immediately disengaged when the distractor does not contain target’s defining attribute. Signal suppression hypothesis posits that a salient distractor can automatically produce a bottom-up “attend-to-me” signal, but this signal can be suppressed via top-down control processes so that it does not actually capture attention. The empirical evidence of the rapid disengagement hypothesis indicated that the spatial-cuing paradigm and oculomotor disengagement paradigm were most often adopted, and participants took the singleton search strategy. The empirical evidence of the signal suppression hypothesis indicated that the additional singleton paradigm was most often adopted, and participants were forced to take the feature search strategy. In the future, more studies adopting different stimuli and experimental methods are needed to support those two hybrid models. The effects of reward and training on “attentional capture-disengagement” and “signal-suppression” should also be explored in future research.

Visual imagery influences attentional guidance during visual search: Behavioral and electrophysiological evidence.

Recent behavioral studies have shown that color imagery can benefit visual search when it is congruent with an upcoming target. In the present study we investigated whether this color imagery benefit was due to the processes underlying attentional guidance, as indicated by the electrophysiological marker known as the N2pc component. Participants were instructed to imagine a color prior to each trial of a singleton search task. On some trials, the imagined color was congruent with the target, and on other trials, it was congruent with the distractors. The analyses revealed that the N2pc was present when color imagery was congruent with the search target, and absent when it was congruent with the distractors. Further, there was preliminary evidence that attentional guidance depended on the vividness of color imagery and the frequency at which participants implemented the imagery instruction. Overall, the results of the present study indicate that color imagery can influence the attentional guidance processes underlying visual search.

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.