Guided Search 6.0: An updated model of visual search

Biased competition between action representations

We propose a generalized version of the biased competition account of attention that may be applied to all domains of cognition. Based on our Generalized Biased Competition account, we propose a formal race model of selection of action representations. The model explains how action representations stored in long-term memory are competing for selection based on their match to the current environmental context and their importance weight. We then present results and model fits from three experiments using a recently developed multiple cue paradigm where several attention shifts with different associated reward values are competing. We show that participants were surprisingly efficient at selecting both when the number of cues and the number of possible reward values were increased. Only when we manipulated reward contingencies and knowledge of these, did the participants show suboptimal performance. The new Generalized Biased Competition account can also explain failures of executive control exemplified by goal neglect where instructions fail to influence behavior despite being retrievable. Finally, we argue that our model may provide a unified understanding of intentions, routines, and habits. Specifically, intentions, routines, and habits may be understood as a continuous range of the same fundamental form of action representation but with variation in their strength of long-term memory traces and importance weights.

Visual statistical learning requires attention

Statistical learning is a person's ability to automatically learn environmental regularities through passive exposure. Since the earliest studies of statistical learning in infants, it has been debated exactly how "passive" this learning can be (i.e., whether attention is needed for learning to occur). In Experiment 1 of the current study, participants performed a serial feature search task where they searched for a target shape among heterogenous nontarget shapes. Unbeknownst to the participants, one of these nontarget shapes was presented much more often in location. Even though the regularity concerned a nonsalient, nontarget item that did not receive any attentional priority during search, participants still learned its regularity (responding faster when it was presented at this high-probability location). While this may suggest that not much, if any, attention is needed for learning to occur, follow-up experiments showed that if an attentional strategy (i.e., color subset search or exogenous cueing) effectively prevents attention from being directed to this critical regularity, incidental learning is no longer observed. We conclude that some degree of attention to a regularity is needed for visual statistical learning to occur.

Large-scale functional networks underlying visual attention

Attention networks are loosely defined as the regions of the brain which interact to control behaviour during attentional tasks, but the specific definition of attention networks varies between research programs based on task demands and modalities. The Attention Network Task was designed to exemplify three aspects of attention, alerting, orienting, and executive control, using a visual cueing paradigm. Its proponents propose a system of networks which underlies these aspects. It is debated whether there exists a unified system of networks which underlies attention independently of other cognitive and sensory processing systems. We review the evidence for an attention system within the domain of visual attention. Neuroimaging research using fMRI, EEG, MEG, and others across a variety of tasks attributed to attention, visual cueing, visual search, and divided attention, is compared. This concludes with a discussion on the limitations of an independent "attention system" for describing how the brain flexibly controls many abilities attributed to visual attention.

Statistical Context Learning in Visual Search: Distinct Electrophysiological Signatures of Contextual Guidance and Context Suppression

Facilitation of visual search by repeated distractor contexts is typically studied employing distractor configurations that are 100% predictive of the target location. Yet, real-world contexts vary in predictivity. We used electroencephalography (EEG) in human participants of either sex to explore how visual search facilitation arises from two distinct processing modes-contextual guidance and context suppression-that depend on the predictivity of distractor contexts, comparing repeated distractor arrangements that were either predictive or nonpredictive of target location against a baseline of nonrepeated arrangements. In Experiment 1, we manipulated context predictivity by shifting repeated contexts from predictive to nonpredictive and vice versa, while in Experiment 2, we restricted repeated contexts to one side of the display to assess lateralized effects of the two processing modes. Both types of contexts behaviorally facilitated visual search, but facilitation was larger with predictive contexts. Making predictive contexts nonpredictive reduced the facilitation while rendering nonpredictive contexts predictive failed to produce gains. Half-display predictive contexts facilitated target detection on both sides, while nonpredictive contexts facilitated same-side target detection only. EEG analyses revealed that predictive contexts triggered an early N1pc (guidance signal), followed by an enhanced N2pc (attentional selection) and an increased contralateral delay activity (CDA, indexing working memory processing of the target) in occipitoparietal regions, indicative of contextual guidance boosting the entire processing chain. In contrast, nonpredictive contexts produced only an increased N2pc accompanied by reduced CDA, consistent with context suppression. These differential patterns demonstrate contextual guidance and context suppression to operate as electrophysiologically distinct processing modes.

Age-invariant benefits of spatiotemporal predictions amidst distraction during dynamic visual search

Visual search tasks are widely used to study attention amidst distraction, often revealing age-related differences. Research shows older adults typically exhibit poorer performance and greater sensitivity to distraction, reflecting declines in goal-driven attention. However, traditional search tasks are static and fail to capture the challenges and opportunities in natural environments, which include predictive structures within extended contexts. We designed a search variation where targets and distractors compete over time and embedded spatiotemporal regularities afford prediction-led guidance of attention. Critically, we manipulated the number of distractors to chart how benefits of expectations and deficits from distraction varied with age. Younger and older adults searched for multiple targets as they faded in and out of the display while varying the number of distracting elements between trials. Half the targets appeared at the same time and approximate locations and could be predicted. While we found evidence for decrement and elevated sensitivity to distraction with increasing age, benefits from predictions occurred in all groups. Interestingly, regardless of age, effects of predictions were only significant during periods of high distraction. This work extends our understanding of attention control through ageing to dynamic settings and indicates a dissociation between goal-directed and learning-driven attentional guidance.

A large neuronal dataset for natural category-based free-gaze visual search in macaques

Goal-directed visual attention is a fundamental cognitive process that demonstrates the brain's remarkable ability to prioritize visual information relevant to specific tasks or objectives. Despite its importance, there is a lack of comprehensive datasets to investigate the underlying neural mechanisms. Here, we present a large naturalistic visual search dataset in which rhesus macaques searched for targets among natural stimuli based on object categories using voluntary eye movements. The stimulus set included 40 images per category across four categories: faces, houses, flowers, and hands. We recorded activity from 6871 units in area V4, 8641 units in the inferior temporal cortex (IT), 5622 units in the orbital frontal cortex (OFC), and 9916 units in the lateral prefrontal cortex (LPFC). These units exhibited diverse receptive fields and selectivity for visual categories. Together, our extensive dataset provides a rich neuronal population across multiple brain areas, enabling a comprehensive analysis of the neural processes underlying goal-directed visual attention.

Easy does it: Selection during interactive search tasks is biased towards objects that can be examined easily

It is well understood that attentional selection is required to deploy visual attention to relevant objects within displays during visual search tasks. Interactive search, an extension of visual search, refers to tasks wherein an individual must manipulate items within their environment to uncover obscured information whilst searching for a target object. Here, we conducted two independent interactive search experiments where participants were asked to interact with virtual cubes to locate a target T shape embedded onto the side of one of the cubes. Our goal here was to investigate the drivers of attentional selection within interactive searches. To do so, we manipulated the effort required to rotate cubes (Experiment 1) and the quantity of shapes attached to the cubes (Experiment 2). Our findings suggest that the perceived effort required to interact with an object is an extremely strong driver of attentional selection within interactive search behaviors. Here, targets may be slower to be detected when that target is obscured within or by an object that conveys, in some shape or form, greater difficulty to examine compared with other objects. These findings provide an exciting first step towards understanding the factors that influence selection during interactive searches. Data and experimental code for all experiments in this study can be accessed online via this web address: https://osf.io/2zyvf/?view_only=ae4f4f2c36ab4e6aae5da3e99fb81988 . Experiments were not preregistered.

Attention to complex scene features

In daily visual experiences, the human visual system extracts functionally meaningful features from the visual environment to perform necessary cognitive tasks. How does visual attention operate in such complex environments? Would conventional attention theories, such as feature integration theory (FIT) and guided search (GS), apply to such scene features? These theories provide a framework for how selective attention parses visual input into basic features and binds those features into integral percepts. This theoretical framework so far been tested mainly with basic, localized features, such as colour and orientation. Here, we investigate to what extent the FIT and GS framework generalizes to ecologically valid scene features. We conducted a series of visual search experiments in which participants searched for a target scene among distractor scenes. These scenes were generated within a two-dimensional parametric space of high-level scene features, such as indoor lighting, scene layout, or surface texture. We sampled target and distractor scenes from this space in such a way that we could compare feature and conjunction search behaviours. Visual search performance across different set sizes showed that 1) search was never efficient, both feature and conjunction search conditions exhibited set size effects, but 2) feature search was significantly more efficient than conjunction search. Given these results, we propose that real-world scene features are not preattentive, requiring selective attention for successful visual search. However, these features still meaningfully guide attention in a manner consistent with GS.

Mixing it up: Intermixed and blocked visual search tasks produce similar results

We have decades of visual search data from experiments where observers look for targets among distractors. Typically, observers are tested in blocks of several hundred trials, and conclusions about underlying mechanisms are inferred from Reaction Time × Set Size functions and errors. However, in the real world, searchers almost never search for the same target or the same type of target hundreds of times in a row. You search for cereal, then milk, then a bowl. Do the rules derived from blocks of trials apply when search tasks are mixed? Here, we compare mixed and blocked conditions in five experiments. In Experiment 1, four different feature searches are tested. In Experiments 2 and 3, the target was the same in four tasks that were defined by different distractor sets. In Experiment 4, different targets are searched for amongst distractors that remained constant across trials. Finally, in Experiment 5, we allowed participants to choose which of four tasks to perform on each trial. In each experiment, there was no qualitative change in search behavior as a function of the mixed/blocked manipulation. The results support the generality of rules of search learned from blocked trials. However, these results do pose a challenge to simple adaptive models of search termination.

Top-down categorical information can be utilized in distractor suppression

Studies of attention have found behavioral benefits when observers are provided with top-down information related to distractor items. This effect is known as distractor suppression and is thought to be an independent process from target guidance. Most studies have focused on salient or singleton cues to elucidate upon the top-down versus bottom-up debate. Here, we examined if distractor suppression applies to categorical cues through three experiments. In Experiment 1, we modeled previously reported paradigms and replicated suppression effects to salient stimuli but with categorical objects. In Experiment 2, stimulus salience was kept constant, and participants were informed that a category of objects was always a distractor. We found distractor suppression effects where response times (RTs) were faster on trials that included the cued distractor category. In Experiment 3, distractor suppression effects were preserved when we utilized a slightly modified target set embedded in categorical objects. The present set of studies indicate that categorical information can be suppressed. The results suggest that attentional guidance may not be reliant on only the weighting of target features when categorical information is known, but also the use of relevant distractor information.

Color singletons are suppressed under serial search, but not abrupt onsets

In the fields of cognitive psychology, two types of stimuli are well known to powerfully capture one's attention: salient, singleton stimuli standing out from its surroundings and abruptly appearing stimuli. The present study compared how these two kinds of attention-capturing stimuli affect visual search tasks. Specifically, we investigated whether the effects of singleton stimuli and abrupt onsets would differ, depending on how visual searches proceed. As a result, significant attentional capture by a singleton stimulus was found when multiple stimuli were processed in parallel within a large attentional window. However, when the degree of serial processing increased, the singleton stimulus was suppressed. By contrast, abrupt onsets consistently captured attention, regardless of how searches proceed. The present study demonstrates distinct mechanisms mediating attentional capture by salient singletons and abrupt onsets and pinpoints the importance of attentional window and search modes on attentional capture.

Noise correlations and neuronal diversity may limit the utility of winner-take-all readout in a pop out visual search task

Visual search involves active scanning of the environment to locate objects of interest against a background of irrelevant distractors. One widely accepted theory posits that pop out visual search is computed by a winner-take-all (WTA) competition between contextually modulated cells that form a saliency map. However, previous studies have shown that the ability of WTA mechanisms to accumulate information from large populations of neurons is limited, thus raising the question of whether WTA can underlie pop out visual search. To address this question, we conducted a modeling study to investigate how accurately the WTA mechanism can detect the deviant stimulus in a pop out task. We analyzed two types of WTA readout mechanisms: single-best-cell WTA, where the decision is made based on a single winning cell, and a generalized population-based WTA, where the decision is based on the winning population of similarly tuned cells. Our results show that neither WTA mechanism can account for the high accuracy found in behavioral experiments. The inherent neuronal heterogeneity prevents the single-best-cell WTA from accumulating information even from large populations, whereas the accuracy of the generalized population-based WTA algorithm is negatively affected by the widely reported noise correlations. These findings underscore the need to revisit the key assumptions explored in our theoretical analysis, particularly concerning the decoding mechanism and the statistical properties of neuronal population responses to pop out stimuli. The analysis identifies specific response statistics that require further empirical characterization to accurately predict WTA performance in biologically plausible models of visual pop out detection.

How robust is categorial distractor suppression? Assessing the impact of additional categories and increased set size

Distractor suppression is the process of utilizing top-down information about distractors to improve search performance. Most studies have utilized simple stimuli and concluded that basic visual features are suppressed. However, recent studies have shown that categorical information can be suppressed, albeit with limited categories and display set sizes. In three experiments, we examined whether suppression for categorical distractors remained robust in more realistic search conditions by increasing the number of categories and display set sizes. Across our experiments, we modified previous experiments' paradigms where participants searched for specific t orientations that were embedded in categorical objects. In Experiment 1, we increased the number of categories. In Experiment 2, we only increased the display set size. In Experiment 3, we increased both the number of categories and the display set size. Response times were faster on trials where the cued distractor category appeared, indicating distractor suppression effects in Experiments 1 and 2 but not Experiment 3. Combined, the results suggest that categorical distractor suppression effects likely occur in more realistic contexts, but other more beneficial search strategies may also be employed with increased task complexity.

Priming of pop-out in the spatial-cueing paradigm

Searching for a unique target is faster when its unique feature repeats than when it changes. The standard account for this priming-of-popout (PoP) phenomenon is that selecting a target increases the attentional priority of its features in subsequent searches. However, empirical tests of this priority account have yielded contradictory findings. Here, we attempted to clarify why support of its predictions has been elusive in spatial-cueing studies. We noted that the repetition manipulation is stronger in PoP studies than in spatial-cueing studies: The target and nontarget features either repeat or swap in the former, whereas in the latter, the target color either repeats or changes while the nontarget color remains constant. Here, we implemented the stronger repetition manipulation in the spatial-cueing paradigm. If PoP affects attentional priority, the cue-validity effect should be larger when the current-cue color and previous-target color match than when they mismatch. The results of Experiment 1 revealed the opposite effect. Moreover, they showed that well-replicated contingent-capture effects do not hold when target and nontarget colors are allowed to swap-an observation that was confirmed in Experiment 2. In Experiment 3, we verified that with our experimental set-up, a subtle manipulation of attentional priority could modulate cue-validity effects. While the present study does not resolve why evidence for the priority account is inconsistent with the spatial-cueing paradigm, they eliminate one possible reason for such inconsistency. They also reveal that allowing the target and distractors color to swap masks contingent-capture effects, thereby highlighting the complexity of spatial-cueing effects.

Attentional misguidance from contextual learning after target location changes in natural scenes

Attentional orienting in complex visual environments is supported by statistical learning of regularities. For instance, visual search for a target is faster when a distractor layout is repeatedly encountered, illustrating that learned contextual invariances improve attentional guidance (contextual cueing). Although contextual learning is usually relatively efficient, relocating the target (within an otherwise unchanged layout) typically abolishes contextual cueing, while revealing only a slow recovery of learning. However, such a "lack-of-adaptation" was usually only shown with artificial displays with target/distractor letters. The current study in turn used more realistic natural scene images to determine whether a comparable cost would also be evident in real-life contexts. Two experiments compared initial contextual cueing and the subsequent updating after a change in displays that either presented artificial letters, or natural scenes as contexts. With letter displays, an initial cueing effect was found that was associated with non-explicit, incidental learning, which vanished after the change. Natural scene displays either revealed a rather large cueing effect that was related to explicit memory (Experiment 1), or cueing was less strong and based on incidental learning (Experiment 2), with the size of cueing and the explicitness of the memory representation depending on the variability of the presented scene images. However, these variable initial benefits in scene displays always led to a substantial reduction after the change, comparable to the pattern in letter displays. Together, these findings show that the "richness" of natural scene contexts does not facilitate flexible contextual updating.

Responses guide attention

Internalizing regularities between motor responses and stimuli is crucial for adaptive functioning. However, the influence of these regularities on attentional selection remains poorly understood. This study explored whether responses, which predict the locations of search targets, direct attention toward these associated locations, a phenomenon termed response-induced attention. The experiments consist of acquisition and test phases. In the acquisition phase, participants performed a dual task involving an identification task followed by a search task. In the identification task, participants responded to the color of an object presented at the center. Immediately after this response, a search target appeared on either the left or right side. Critically, the response for the identification target predicted a more probable location of the search target. Faster responses for search targets were observed at the response-cued location than the other location, suggesting an attentional bias toward the response-cued location. In the test phase, the colors of identification targets were changed, and the responses for the identification targets were no longer informative about the search target locations. Nevertheless, search remained faster when targets appeared at the response-cued location, suggesting that responses, not colors, guided attention. This response-induced attention effect was observed in Experiment 1, where responses predicted spatially compatible target locations, as well as in Experiments 2 and 3, where they predicted incompatible locations. Experiment 4 confirmed that the observed effects resulted from the spatial distribution of attention. These findings provide new insights into the ability to learn response-stimulus regularities for the intelligent allocation of attention, demonstrating the significant role of the motor dimension in attentional selection.

A model of thalamo-cortical interaction for incremental binding in mental contour-tracing

Object-basd visual attention marks a key process of mammalian perception. By which mechanisms this process is implemented and how it can be interacted with by means of attentional control is not completely understood yet. Incremental binding is a mechanism required in demanding scenarios of object-based attention and is experimentally well investigated. Attention spreads across a representation of the visual object and labels bound elements by constant up-modulation of neural activity. The speed of incremental binding was found to be dependent on the spatial arrangement of distracting elements in the scene and to be scale invariant giving rise to the growth-cone hypothesis. In this work, we propose a neural dynamical model of incremental binding that provides a mechanistic account for these findings. Through simulations, we investigate the model properties and demonstrate how an attentional spreading mechanism tags neurons that participate in the object binding process. They utilize Gestalt properties and eventually show growth-cone characteristics labeling perceptual items by delayed activity enhancement of neuronal firing rates. We discuss the algorithmic process underlying incremental binding and relate it to our model computations. This theoretical investigation encompasses complexity considerations and finds the model to be not only of explanatory value in terms of neurophysiological evidence, but also to be an efficient implementation of incremental binding striving to establish a normative account. By relating the connectivity motifs of the model to neuroanatomical evidence, we suggest thalamo-cortical interactions to be a likely candidate for the flexible and efficient realization suggested by the model. There, pyramidal cells are proposed to serve as the processors of incremental grouping information. Local bottom-up evidence about stimulus features is integrated via basal dendritic sites. It is combined with an apical signal consisting of contextual grouping information which is gated by attentional task-relevance selection mediated via higher-order thalamic representations.

Color-color feature guidance in visual search

Previous work has demonstrated that when the target and distractors differ in two features across different dimensions (e.g., red and square), search can unfold in parallel in either a simultaneous or a sequential feature-guidance manner. However, the underlying mechanism of how two features within a single feature dimension guide search remains elusive. This study specifically aims to explore how two colors, arranged in a center-surround configuration (e.g., red center/green surround), guide search. Our investigation encompasses homogeneous (Experiments 1-3) and heterogeneous (Experiment 4) search displays. Experiment 1 demonstrated a parallel search mechanism with a two-color location-bound search template by using a search display containing distractors that have inverse color relation with the target. Experiments 2 revealed a strategic preference for using a single color to guide search without location binding when distractor types were intermixed across trials, and this preference persisted even when the template was emphasized by presenting it before each trial. Furthermore, Experiment 3 illustrated that, with fixed-distractor practice, participants can acquire a two-color location-bound search strategy. Once in place, this strategy persists, even when the distractor types become intermixed in subsequent blocks of trials. Experiments 4A-D used a computational modeling approach and found that two-color guidance search works in a parallel sequential manner in heterogeneous displays. Participants utilize one of the two target colors first in a location-bound manner to filter out one subset of distractors and then attended to the second target color (location bound) to reject the remaining distractors.

Dominant as Underdogs: Inefficient Search for Dominant-Looking Faces

Detecting dominant individuals within crowds is crucial for human survival, prompting investigation into the tension between quick detection and careful recognition of dominant faces. In our visual search tasks, participants located a target face with a specific identity, with dominance being task-irrelevant. Targets varied in dominance (high or low), and the dominance congruency between targets and distractors was manipulated. Results showed more efficient search when targets differed from distractors by dominance, suggesting leverage of latent dominance contrast. Surprisingly, searching for high-dominance faces exhibited lower efficiency. Experiment 2 replicated these findings and incorporated eye-tracking, revealing longer distractor inspection, more revisits to target faces, and prolonged identification times for high-dominance face searches. Experiment 3 showed search inefficiency even with only dominant faces' eye regions, underscoring the role of local features. Our findings offer a nuanced perspective on how perceived dominance influences cognition and behavior, challenging the assumed ease of dominance detection.

Inference About Absence as a Window Into the Mental Self-Model

To represent something as absent, one must know that they would know if it were present. This form of counterfactual reasoning critically relies on a mental self-model: a simplified schema of one's own cognition, which specifies expected perceptual and cognitive states under different world states and affords better monitoring and control over cognitive resources. Here I propose to use inference about absence as a unique window into the structure and function of the mental self-model. I draw on findings from low-level perception, visual search, and long-term memory, in support of the idea that self-knowledge is a computational bottleneck for efficient inference about absence, and show that alternative "direct perception" and "heuristic" accounts either fail to account for empirical data, or implicitly assume a self-model. I end with a vision for an empirical science of self-modelling, where inference about absence provides a cross-cutting framework for probing key features of the mental self-model that are not accessible for introspection.

Spatial Processing Enhancement in the Prefrontal Cortex for Rapid Detection of Valuable Objects

It is recently shown that objects with long-term reward associations can be efficiently located during visual search. The neural mechanism for valuable object pop-out is unknown. In this work, we recorded neuronal responses in the ventrolateral prefrontal cortex (vlPFC) with known roles in visual search and reward processing in macaques while monkeys engaged in efficient versus inefficient visual search for high-value fractal objects (targets). Behavioral results and modeling using multialternative attention-modulated drift-diffusion indicated that efficient search was concurrent with enhanced processing for peripheral objects. Notably, neural results showed response amplification and receptive field widening to peripherally presented targets in vlPFC during visual search. Both neural effects predict higher target detection and were found to be correlated with it. Our results suggest that value-driven efficient search independent of low-level visual features arises from reward-induced spatial processing enhancement of peripheral valuable objects.

Cognitive control during scene categorization: The role of identity repetition and timing in congruence sequence effects

Cognitive control abilities include maintaining goal-directed behaviors in spite of the incongruence between habitual and desired responses. In interference paradigms, slower responses to incongruent compared to congruent trials are observed; this interference is reduced after incongruent trials (congruence sequential effect, CSE), suggesting that the control exerted to counteract interference in the previous trial also propagates into the following trial. Moreover, a larger CSE is observed when trial features are repeated. Binding-retrieval accounts suggest that trial features that occur in the same time frame are bound together in an episodic representation; if a feature is repeated in the next trial, the control state that was active in the previous trial is also reactivated, resulting in a modulation of congruence effects. However, previous studies that used stimulus sets characterized by intracategory variability (e.g., faces and scenes) observed CSE modulation by the repetition of response categories but were inconclusive concerning whether repeating the identity of a stimulus may modulate CSE. The present study investigates whether episodic stimulus representations include both stimulus identity and response category information, by comparing the impact of the repetition of novel pictures (no identity repetition) and of frequent pictures (in which identity is repeated over trials) in a picture-word interference task. Results indicated that stimulus identity was not critical in the modulation of CSE, and that CSE was little affected by response-stimulus interval. Altogether, the present results contribute to the understanding and theoretical specification of sequential effects.

A tutorial review on methods for collecting similarity judgments from human observers

Similarity is a central concept in the study of cognition, having been identified as an explanatory factor in the dynamics of myriad psychological phenomena. The collection of similarity judgments, however, can be a difficult, laborious, and time-consuming process. There is presently a vast and diverse array of methodologies applied throughout the psychological sciences from which to gather judgments of similarity perceptions, and each carries its own relative advantages and disadvantages. Each method may be suitable for a specific set of contexts and stimuli but be inappropriate for others. This tutorial review is meant to serve as a guided tour of common similarity judgment-gathering methods currently utilized in the psychological sciences, and to provide an overview of how and when researchers should leverage them.

Template-based attentional guidance and generic procedural learning in contextual guided visual search: Evidence from reduced response time variability

The contextual cueing effect-where participants search repeated displays faster than novel ones-is often explained by the "attention guidance" account, which posits that repeated exposure helps individuals learn the context and attend to the likely target locations. Alternatively, the "generic procedural learning" account suggests that a general search strategy is developed for all displays, although repeated contexts play a higher weight in optimizing the strategy due to their higher presented frequency. This makes responses faster for repeated displays than novel displays. The current study examined these two mechanisms using a varied contextual cueing paradigm to analyze response time (RT) variability with the coefficient of variation (CV) and time-frequency analysis of RTs. Experiment 1 involved uninterrupted training with repeated and novel displays presented separately, followed by a test with randomly interleaved repeated and novel displays. Experiment 2 used interleaved displays for training before an uninterrupted test phase. Both experiments revealed faster RTs and reduced template-based variability for repeated displays early in the training, supporting attentional guidance. However, generic procedural learning, indicated by a late onset of lower cross-display variability for repeated displays, required more time and training to validate the cueing effect. These findings suggest that attentional guidance dominates early learning, but both mechanisms contribute to the contextual cueing effect overall.

Inhibition in large set sizes depends on search mode, not salience

Attention can be attracted to salient items in a visual scene. Recent studies have shown that when the feature of an irrelevant salient item is known, it can be suppressed below baseline leading to facilitated search. Wang and Theeuwes (Experimental Psychology: Human Perception and Performance, 46(10), 1051-1057, 2020) criticised previous inhibition studies by claiming that the sparse displays attenuated the salience of the distractors. In their study they increased the number of display items (i.e., set size), and found that an irrelevant salient distractor captured attention. The current paper argues that the displays used by Wang and Theeuwes encouraged participants to use a singleton search mode, in which participants actively look for salient regions to find the target and consequently do not inhibit salient items. Specifically, their displays included multiple repeated non-target shapes, so that the target became a singleton. We used two search displays with ten items, one with repeated non-targets (R-NT displays), allowing a singleton search mode, and one with heterogeneous non-targets, encouraging a feature search mode. In Experiment 1 the singleton distractor was inhibited in the heterogeneous condition, but not in the R-NT condition. Experiment 2 intermixed the two display types in unbalanced blocks. When the majority of trials had heterogeneous non-targets, inhibition was observed for both the heterogeneous displays and the R-NT displays. Conversely, when R-NT displays were the majority, inhibition was attenuated for both display types. These results show that distractor features can be suppressed at large set sizes dependant on the search strategy promoted by the displays.

Distinct attentional characteristics of neurons with visual feature coding in the primate brain

Visual attention and object recognition are two critical cognitive functions that shape our perception of the world. While these neural processes converge in the temporal cortex, the nature of their interactions remains largely unclear. Here, we systematically investigated the interplay between visual attention and stimulus feature coding by training macaques to perform a free-gaze visual search task with natural stimuli. Recording from a large number of units across multiple brain areas, we found that units exhibiting visual feature coding showed stronger attentional modulation of responses and spike-local field potential coherence than units without feature coding. Across brain areas, attention directed toward search targets enhanced the neuronal pattern separation of stimuli, with this enhancement more pronounced for units encoding visual features. Together, our results suggest a complex interplay between visual feature and attention coding in the primate brain, likely driven by interactions between brain areas engaged in these processes.

Evaluating the contribution of parallel processing of color and shape in a conjunction search task

Traditionally, researchers interpret the difficulty in conjunction search as difficulty in binding features. In the present study, we used a behavioral-computational approach to assess if parameters from feature search could predict performance in a color-shape conjunction search task. We also investigated whether pooling-mediated processing in peripheral regions was a key-limiting factor in performance in conjunction search by manipulating display arrangements across different experiments. The results indicated that parameters in homogeneous search displays can indeed be used to successfully predict performance in conjunction search displays. This finding is noteworthy because it indicates that the visual system must be extracting the same information from the display in feature and conjunction search tasks (i.e., the target-distractor similarity) using color and shape. Furthermore, there was no compelling evidence that pooling-mediated processing was the primary constraint on performance in this conjunction search task. A model-comparison approach compared the accuracy of different distractor rejection architectures in predicting performance in conjunction search tasks. The winning model showed participants engaging hierarchically with the display, selecting and rejecting distractor subsets based on a single defining feature. Taken in the context of previous research on heterogeneous search performance, the current results imply that the inherent demands of search for a conjunction of color and shape compel participants to adopt this targeted search strategy.

Learning of the mean, but not variance, of color distributions cues target location probability

Humans are good at picking up statistical regularities in the environment. Probability cueing paradigms have demonstrated that the location of a target can be predicted based on spatial regularities. This is assumed to rely on flexible spatial priority maps that are influenced by visual context. We investigated whether stimulus features such as color distributions differing in mean and variance can cue location regularities. In experiment 1, participants searched for an oddly colored target diamond in a 6 × 6 set. On each trial, the distractors were drawn from one of two color distributions centered on different color averages. Each distribution was associated with different target location probabilities, one distribution where the target had an 80% chance to appear on the left (the rich location), while the rich location would be on the right for the other distribution. Participants were significantly faster at locating the target when it appeared in the rich location for both distributions, demonstrating learning of the relationship between color average and location probability. In experiments 2 and 3, observers performed a similar search task, but the distributions had different variances with the same average color. There was no evidence that search became faster when the target appeared in a rich location, suggesting that contingencies between target probabilities and color variance were not learned. These results demonstrate how statistical location learning is flexible, with different visual contexts leading to different spatial priority maps, but they also reveal important limits to such learning.

Coarse matching was sufficient to capture attention by working memory representations unless matching features with the target

BACKGROUND

In most theoretical frameworks, the effectiveness of attentional selection relies significantly on the perceptual similarity between the target template and visual input. Nevertheless, ambiguity exists surrounding whether attentional capture triggered by irrelevant representations in Working Memory (WM) is influenced by the perceptual similarity levels of features between WM content and its matching distractors.

METHODS

We designed a hybrid WM and visual search task, varying such perceptual similarity of colors across three levels: exact, high-similar, and low-similar matching. To quantify the extent of the capture effect, we compared these conditions against a neutral baseline (i.e., completely different color) using eye movement and behavioral data in two experiments.

RESULTS

We consistently observed robust attentional capture effects across two experiments, evident in both eye movement indices and manual reaction times. In Experiment 1, where WM representations solely matched features to visual search distractors (task-irrelevant scenario), we found that changes in perceptual similarity did not influence attentional capture. Conversely, in Experiment 2, where WM representations had the potential to match the visual search target (task-relevant scenario), we observed a significantly more robust attentional capture effect for high-similar matching compared to low-similar matching conditions.

CONCLUSIONS

These findings imply that coarse matching between distractors and WM contents is sufficient to capture attention, unless the matching features potentially correspond to the visual target. Furthermore, task relevance sharpens perceptual sensitivity to visual input, highlighting distinct mechanisms underlying attentional capture by irrelevant representations and target templates within WM.

Attentional capture by abrupt onsets: Foundations and emerging issues

The study of attentional allocation due to external stimulation has a long history in psychology. Early research by Yantis and Jonides suggested that abrupt onsets constitute a unique class of stimuli that captures attention in a stimulus-driven fashion unless attention is proactively directed elsewhere. Since then, the study of visual attention has evolved significantly. This article revisits the core conclusions by Yantis and Jonides in light of subsequent findings and highlights emerging issues for future investigation. These issues include clarifying key concepts of visual attention, adopting measures with greater spatiotemporal precision, exploring how past experiences modulate the effects of abrupt onsets, and understanding individual differences in attentional allocation. Addressing these issues is challenging but crucial, and we offer some perspectives on how one might choose to study these issues going forward. Finally, we call for more investigation into abrupt onsets. Perhaps due to their strong potential to capture attention, abrupt onsets are often set aside in pursuit of other conditions that show attenuation of distractor interference. However, given their real-world relevance, abrupt onsets represent the exact type of stimuli that we need to study more to connect laboratory attention research to real life. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

EEG evidence for spatial selectivity in feature-based preparation for visual search

In many visual search tasks, the detection of target objects in visual search requires feature-selective attentional guidance and space-based attentional selection. Feature-based attention is often assumed to operate in a spatially global fashion across the entire visual field, but there is also evidence that it can be restricted to task-relevant locations under some conditions. Here, we investigated whether such spatial filtering processes are already evident when representations of target-defining features (attentional templates) are activated during the preparation for an upcoming search episode. We measured N2pc components (an electrophysiological index of attentional allocation) in response to a rapid series of lateral task-irrelevant but template-matching colour probes that appeared while participants prepared for an upcoming search task with colour-defined targets. Critically, search targets would either always appear in the same lateral regions of visual space as the probes, or at different locations (near fixation or in lateral areas that never contained probes), thus rendering the probed locations either task-relevant or irrelevant. N2pc components triggered by target-colour probes during the preparation period emerged later and were attenuated when probes were presented at irrelevant locations. This demonstrates that the effects of preparatory feature-based attentional templates can be modulated by spatial expectations. However, this type of spatial filtering during search preparation only attenuates but not completely eliminates feature-based attentional modulations.

Differential Neural Mechanisms Underlying Inhibition of Color and Dynamic Motion Distractors

Navigating visually complex environments requires focusing on relevant information while filtering out (salient) distractions. The signal suppression hypothesis posits that salient stimuli generate an automatic saliency signal that captures attention unless overridden by learned suppression mechanisms. In support of this, ERP studies have demonstrated that salient stimuli that do not capture attention elicit a distractor positivity (PD), a putative neural index of suppression. Yet, to date, this hypothesis has been primarily tested with color singletons, leaving it unclear if the PD reflects general suppression or is specific to color singletons. This study compared lateralized ERPs elicited by color singleton and dynamic motion distractors using a variant of the additional singleton paradigm that has been shown to result in proactive suppression of colored distractors. Behavioral results showed a singleton presence benefit for both distractor types, indicating distractor suppression. However, ERP data revealed clear differences in the underlying neural mechanisms: Color singletons elicited a PD component indicative of proactive suppression, whereas motion singletons elicited a later positivity preceded by an N2pc, suggesting reactive suppression. Our findings suggest that motion singletons, unlike color singletons, are suppressed reactively after initial capture. This study highlights the importance of considering distractor feature dimensions in understanding attentional suppression mechanisms and underscores the need for caution in establishing proactive suppression based on a single metric. Further research is needed to clarify the conditions under which the early PD reliably indicates proactive suppression and to explore the neural processes underlying the suppression of various salient distractors.

Physically activated modes of attentional control

As we navigate through the day, our attentional control processes are constantly challenged by changing sensory information, goals, expectations, and motivations. At the same time, our bodies and brains are impacted by changes in global physiological state that can influence attentional processes. Based on converging lines of evidence from brain recordings in physically active humans and nonhumans, we propose a new framework incorporating at least two physically activated modes of attentional control in humans: altered gain control and differential neuromodulation of control networks. We discuss the implications of this framework for understanding a broader range of states and cognitive functions studied both in the laboratory and in the wild.

Examining Limits of Small Multiples: Frame Quantity Impacts Judgments With Line Graphs

Small multiples are a popular visualization method, displaying different views of a dataset using multiple frames, often with the same scale and axes. However, there is a need to address their potential constraints, especially in the context of human cognitive capacity limits. These limits dictate the maximum information our mind can process at once. We explore the issue of capacity limitation by testing competing theories that describe how the number of frames shown in a display, the scale of the frames, and time constraints impact user performance with small multiples of line charts in an energy grid scenario. In two online studies (Experiment 1 n = 141 and Experiment 2 n = 360) and a follow-up eye-tracking analysis (n = 5), we found a linear decline in accuracy with increasing frames across seven tasks, which was not fully explained by differences in frame size, suggesting visual search challenges. Moreover, the studies demonstrate that highlighting specific frames can mitigate some visual search difficulties but, surprisingly, not eliminate them. This research offers insights into optimizing the utility of small multiples by aligning them with human limitations.

Electrophysiological evidence for the optimal tuning of attention

Optimal tuning of attention refers to shifts in goal-driven attention that increase the difference between the representation of the target and nontarget features. Evidence for optimal tuning comes from studies measuring the memory representation of the target and, to a lesser degree, from studies measuring attentional selectivity. In one study on attentional selectivity, cueing effects were found to be greater for cue colors deviating away from the nontarget color compared to cue colors deviating toward the nontarget color, suggesting that participants' search goal was optimally tuned. To address alternative accounts, we measured event-related potentials (ERPs) elicited by different cue colors at posterior electrodes PO7/PO8. We found that ERPs associated with attentional orienting (N1pc) or selection (N2pc) were larger for cue colors deviating away from the nontarget color, which is consistent with the optimal tuning of attention. In contrast, the results are difficult to reconcile with alternative accounts such as rapid disengagement or object updating. Further, we aimed to evaluate contributions from sensory adaptation by analyzing the Ppc component, a lateralized ERP in the P1 time range. Two control conditions, however, suggested that the Ppc was more likely driven by imbalanced saliency than sensory adaptation.

Accentuation and Attention: From Perceptual Organization to Consciousness

Background: This study investigates the complex relationship between accentuation and attention in visual perception, extending classical Gestalt principles by introducing dissimilarity as a complementary mechanism to similarity in perceptual organization. Objectives and Methods: Through a series of phenomenological experiments, we demonstrate how accentuation, driven by dissimilarity, plays a crucial role in shaping visual experience and guiding attention. Results: Our findings reveal that accentuation serves as a pre-attentive mechanism for highlighting salient features, influencing initial perceptual organization, and modulating the apparent shape and orientation of visual elements. We show that while accentuation operates rapidly and automatically, attention acts as a flexible, selective mechanism that can either reinforce or override accentuation-based percepts. This interplay suggests a two-stage process of visual perception, with implications for theories of consciousness and information processing in biological systems. This study also explores the evolutionary significance of accentuation in camouflage and sexual selection, providing insights into how perceptual mechanisms may have evolved to enhance adaptive fitness. Conclusions: Our results have broad implications for understanding visual cognition, design, and clinical applications related to attentional disorders.

Computational modelling reveals the influence of object similarity and proximity on visually guided movements

The paper aims to understand how humans reach for a single target object in multi-object scenes. In a previous empirical study, human subjects were asked to execute reaches to a single target among non-targets (choice reaching task). In the current work, we re-analysed the human data and implemented a neurobiologically-plausible cognitive robotics model (choice reaching with a LEGO arm robot, CoRLEGO) that mimics human reaches in the choice reaching task. The results from the experiment confirmed the commonly made assumption that proximity and similarity between objects (also termed perceptual grouping) affect the quality of the reaches. However, what was novel here was that modelling the reaches also allowed to temporally separate these factors, as the start of the movement was affected by both factors while the reach trajectory was affected only by proximity between target and distractor objects indicating that human information processing of visual stimuli applies these factors in a serial fashion. In particular, our model architecture and the optimised parameter settings suggest that object proximity directly influences the movement onset. In addition, our computational model confirmed this interpretation but also revealed that the relationship between the two factors may be affected by how the participants balanced speed (starting time of the movement) and accuracy of reaching (straightness of reaches). Future research will need to test whether this plausible prediction is correct.

Likelihood Systems Can Improve Hit Rates in Low-Prevalence Visual Search Over Binary Systems

OBJECTIVE

To study the performance consequences of binary versus likelihood decision support systems in low-prevalence visual search.

BACKGROUND

Hit rates in visual search are often low if target prevalence is low, an issue that is relevant for numerous real-world visual search tasks (e.g., luggage screening and medical imaging). Given that binary decision support systems produce many false alarms at low prevalence, they have often been discounted as a solution to this low-prevalence problem. By offering additional information about the certainty of target-present indications through splitting these into warnings and alarms, likelihood-based systems could potentially boost hit rates without raising the number of false alarms.

METHOD

We used a simulated medical search task with low target prevalence in a paradigm where participants sequentially uncovered parts of the stimulus with their mouse. In two sessions, participants completed the task either while being supported by a binary or a likelihood system.

RESULTS

Hit rates were higher when interacting with the likelihood systems than with the binary system, at no cost of higher false alarms.

CONCLUSION

Likelihood systems are a promising way to tackle the low-prevalence problem, and might further be an effective means to make systems more transparent.

APPLICATION

Simple-to-process information about system certainty for each case might be a solution to low hit rates in domains with low target prevalence, such as radiology.

Breaking the silence: Exploring the influence of auditory singularity on visual search

The pip-and-pop effect describes the phenomenon of auditory pure-tone stimuli (pip) causing simultaneously visual target to pop out. This study utilised a dynamic visual search paradigm and conducted two eye movement experiments (Experiment 1: set size = 24 items; Experiment 2: set size = 48 items) to explore the influence of auditory singularity on the Pip-and-Pop effect through single-sound condition (singularity) and multiple-sound condition (non-singularity). In Experiment 1, there were no significant differences between the no-sound, single-sound, and multiple-sound conditions in terms of reaction time, accuracy, or fixation number. In Experiment 2, compared with the no-sound condition, both the single-sound and multiple-sound conditions significantly reduced the Search time (RTs), accuracy, and fixation numbers when the target was present. Both Experiments 1 and 2 revealed that the fixation duration under the single-sound condition was significantly longer than that under the no-sound condition. These findings suggest that the singularity of auditory stimuli is not a necessary condition for the pip-and-pop effect. Audiovisual interaction is more likely to be a prerequisite for the occurrence of the pip-and-pop effect.

A robotics-inspired scanpath model reveals the importance of uncertainty and semantic object cues for gaze guidance in dynamic scenes

The objects we perceive guide our eye movements when observing real-world dynamic scenes. Yet, gaze shifts and selective attention are critical for perceiving details and refining object boundaries. Object segmentation and gaze behavior are, however, typically treated as two independent processes. Here, we present a computational model that simulates these processes in an interconnected manner and allows for hypothesis-driven investigations of distinct attentional mechanisms. Drawing on an information processing pattern from robotics, we use a Bayesian filter to recursively segment the scene, which also provides an uncertainty estimate for the object boundaries that we use to guide active scene exploration. We demonstrate that this model closely resembles observers' free viewing behavior on a dataset of dynamic real-world scenes, measured by scanpath statistics, including foveation duration and saccade amplitude distributions used for parameter fitting and higher-level statistics not used for fitting. These include how object detections, inspections, and returns are balanced and a delay of returning saccades without an explicit implementation of such temporal inhibition of return. Extensive simulations and ablation studies show that uncertainty promotes balanced exploration and that semantic object cues are crucial to forming the perceptual units used in object-based attention. Moreover, we show how our model's modular design allows for extensions, such as incorporating saccadic momentum or presaccadic attention, to further align its output with human scanpaths.

The temporal dynamics of visual attention

Researchers have long debated how humans select relevant objects amid physically salient distractions. An increasingly popular view holds that the key to avoiding distractions lies in suppressing the attentional priority of a salient distractor. However, the precise mechanisms of distractor suppression remain elusive. Because the computation of attentional priority is a time-dependent process, distractor suppression must be understood within these temporal dynamics. In four experiments, we tracked the temporal dynamics of visual attention using a novel forced-response method, by which participants were required to express their latent attentional priority at varying processing times via saccades. We show that attention could be biased either toward or away from a salient distractor depending on the timing of observation, with these temporal dynamics varying substantially across experiments. These dynamics were explained by a computational model assuming the distractor and target priority signals arrive asynchronously in time and with different influences on saccadic behavior. The model suggests that distractor signal suppression can be achieved via a "slow" mechanism in which the distractor priority signal dictates saccadic behavior until a late-arriving priority signal overrides it, or a "fast" mechanism which directly suppresses the distractor priority signal's behavioral expression. The two mechanisms are temporally dissociable and can work collaboratively, resulting in time-dependent patterns of attentional allocation. The current work underscores the importance of considering the temporal dynamics of visual attention and provides a computational architecture for understanding the mechanisms of distractor suppression. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Getting a grip on visual search: Relating effort exertion to the control of attention

Humans are generally biased to conserve energy, limiting the exertion of physical and mental effort. The need for attention to selectively process perceptual information is a ubiquitous part of mental life, but how mentally effortful is the process of finding the target of a visual search, and how much mental effort is required to focus attention in the face of potentially distracting stimuli? Does learning from demands on physical effort shape the control of attention, much like rewards and punishments? In this tutorial review, we provide an overview of a novel approach to probing the mental effort involved in visual search and the control of attention more generally. Situations are created in which exerting physical effort, via a hand dynamometer, can modify the demands of a visual search task. More specifically, participants can exert physical effort to reduce the putative mental effort required to find a target. When comparing across search conditions, this approach can reveal the conditions that participants are willing to physically work to achieve, with implications for the mental effort associated with these conditions. We also introduce a reciprocal approach in which demands on physical effort, and their association with the visual search task, are manipulated, providing an opportunity to examine how the control of attention is shaped by these effort demands. Some practical considerations for the implementation of these novel approaches are discussed, as are potential new research directions for which these approaches are well suited.

Distractor-response binding influences visual search

Intertrial priming effects in visual search and action control suggest the involvement of binding and retrieval processes. However, the role of distractor-response binding (DRB) in visual search has been largely overlooked, and the specific processing stage within the functional architecture of attentional guidance where the DRB occurs remains unclear. To address these gaps, we implemented two search tasks, where participants responded based on a separate feature from the one defining the target. We kept the target dimension consistent across trials while varying the color and shape of the distractor. Moreover, we either repeated or randomized the target position in different sessions. Our results revealed a pronounced response priming, a difference between trials where the response changed versus repeated, and importantly this response priming was stronger when distractor features or the target position were repeated than when they changed. These insights affirm the presence of DRB during visual search and support the framework of binding and retrieval in action control as a basis for observed intertrial priming effects related to distractor features. All data are available at: https://github.com/msenselab/distractor_binding .

Getting value out of working memory through strategic prioritisation: Implications for storage and control

Working memory is an active system responsible for the temporary maintenance and processing of information in the support of cognition and action. In keeping with this, a growing body of research has explored the close links between working memory and attention, and how these might be harnessed to impact performance and possibly improve working memory efficiency. This is theoretically and practically important, given that working memory is a central hub in complex cognition yet is extremely capacity- and resource-limited. We review work carried out over the last 10 years or so looking at how high "value" items in working memory can be strategically prioritised through selective attention, drawing principally from visual working memory paradigms with young adult participants, while also discussing how the core effects extend to different task domains and populations. A consistent set of core findings emerges, with improved memory for items that are allocated higher value but no change in overall task performance, and a recency advantage regardless of point allocation when items are encountered sequentially. Value-directed prioritisation is effortful, under top-down strategic control, and appears to vary with perceptual distraction and executive load. It is driven by processes operating during encoding, maintenance, and retrieval, though the extent to which these are influenced by different features of the task context remains to be mapped out. We discuss implications for working memory, attention, and strategic control, and note some possible future directions of travel for this promising line of research.

Under pressure in the Eriksen flanker task

A classical observation in experimental psychology is a reduction in reaction time and response accuracy under time pressure (TP). This speed-accuracy tradeoff may be understood from the combined perspectives of affordance competition and urgency gating. This view implies that action programs compete with each other from stimulus onset until the final response. Furthermore, responses are thought to be determined not just by the outcome of this competition but also by the urgency to respond. The latter aspect may play an important role in the case of speed stress. An experiment was conducted employing the Eriksen flanker task with different levels of TP. Behavioral, electromyographic (EMG), and electroencephalographic (EEG) data were registered. In the EEG analysis, source-level time-frequency activity was isolated for three sources (occipito-temporal, motor, and medial-frontal cortex). Inter-source phase coherence was computed to assess the neural dynamics underlying the effects of TP and flanker congruency. The EEG and EMG data revealed that TP affects visuo-motor links and motoric processes, while the flanker congruency effect was present from a very early level up to the final response. The present findings fit well within the combined perspectives of affordance competition and urgency gating.

The degree of parallel/serial processing affects stimulus-driven and memory-driven attentional capture: Evidence for the attentional window account

The issue of whether a salient stimulus in the visual field captures attention in a stimulus-driven manner has been debated for several decades. The attentional window account proposed to resolve this issue by claiming that a salient stimulus captures attention and interferes with target processing only when an attentional window is set wide enough to encompass both the target and the salient distractor. By contrast, when a small attentional window is serially shifted among individual stimuli to find a target, no capture is found. Research findings both support and challenge this attentional window account. However, in these studies, the attentional window size was improperly estimated, necessitating a re-evaluation of the account. Here, using a recently developed visual search paradigm, we investigated whether visual stimuli were processed in a parallel or a serial manner. We found significant attentional capture when multiple stimuli were processed in parallel within a large attentional window. By contrast, when a small window had to be serially shifted, no capture was found. We conclude that the attentional window account can be a useful framework to resolve the widespread debate regarding stimulus-driven attentional capture.

Readiness for Perception and Action: Towards a More Mechanistic Understanding of Phasic Alertness

Human survival requires prompt perception and action to address relevant events in the environment. For this, the brain has evolved a system that uses warning stimuli to elicit phasic alertness, a state readying the brain for upcoming perception and action. Although a wealth of empirical evidence revealed how phasic alertness improves a wide range of perceptual and cognitive processing, it is still unclear by what cognitive mechanisms this is achieved. Here, we identify key problems that have to be solved for this to be possible and delineate concrete ways to achieve this. Specifically, we discover I) how to establish phasic alertness as a cognitive state of readiness for perception and action, II) how it can affect cognition online or offline, III) how it could be triggered internally without a warning, and IV) to what degrees it relied on bottom-up processing, or top-down temporal or stimulus expectations and the current task. As a result, the discussion provides us with a research program yielding the theoretical and empirical basis for mechanistic and computational models of phasic alertness and its neurophysiological underpinnings.

Contributions of distractor dwelling, skipping, and revisiting to age differences in visual search

Visual search becomes slower with aging, particularly when targets are difficult to discriminate from distractors. Multiple distractor rejection processes may contribute independently to slower search times: dwelling on, skipping of, and revisiting of distractors, measurable by eye-tracking. The present study investigated how age affects each of the distractor rejection processes, and how these contribute to the final search times in difficult (inefficient) visual search. In a sample of Dutch healthy adults (19-85 years), we measured reaction times and eye-movements during a target present/absent visual search task, with varying target-distractor similarity and visual set size. We found that older age was associated with longer dwelling and more revisiting of distractors, while skipping was unaffected by age. This suggests that increased processing time and reduced visuo-spatial memory for visited distractor locations contribute to age-related decline in visual search. Furthermore, independently of age, dwelling and revisiting contributed stronger to search times than skipping of distractors. In conclusion, under conditions of poor guidance, dwelling and revisiting have a major contribution to search times and age-related slowing in difficult visual search, while skipping is largely negligible.

Spatial Predictive Context Speeds Up Visual Search by Biasing Local Attentional Competition

The human visual system is equipped to rapidly and implicitly learn and exploit the statistical regularities in our environment. Within visual search, contextual cueing demonstrates how implicit knowledge of scenes can improve search performance. This is commonly interpreted as spatial context in the scenes becoming predictive of the target location, which leads to a more efficient guidance of attention during search. However, what drives this enhanced guidance is unknown. First, it is under debate whether the entire scene (global context) or more local context drives this phenomenon. Second, it is unclear how exactly improved attentional guidance is enabled by target enhancement and distractor suppression. In the present magnetoencephalography experiment, we leveraged rapid invisible frequency tagging to answer these two outstanding questions. We found that the improved performance when searching implicitly familiar scenes was accompanied by a stronger neural representation of the target stimulus, at the cost specifically of those distractors directly surrounding the target. Crucially, this biasing of local attentional competition was behaviorally relevant when searching familiar scenes. Taken together, we conclude that implicitly learned spatial predictive context improves how we search our environment by sharpening the attentional field.

Electrophysiological Correlates of Visual Memory Search

In everyday life, we frequently engage in 'hybrid' visual and memory search, where we look for multiple items stored in memory (e.g., a mental shopping list) in our visual environment. Across three experiments, we used event-related potentials to better understand the contributions of visual working memory (VWM) and long-term memory (LTM) during the memory search component of hybrid search. Experiments 1 and 2 demonstrated that the FN400 (an index of LTM recognition) and the CDA (an index of VWM load) increased with memory set size (target load), suggesting that both VWM and LTM are involved in memory search, even when target load exceeds capacity limitations of VWM. In Experiment 3, we used these electrophysiological indices to test how categorical similarity of targets and distractors affects memory search. The CDA and FN400 were modulated by memory set size only if items resembled targets. This suggests that dissimilar distractor items can be rejected before eliciting a memory search. Together, our findings demonstrate the interplay of VWM and LTM processes during memory search for multiple targets.