Involuntary top-down control by search-irrelevant features: Visual working memory biases attention in an object-based manner

The dominoes of features: Dynamic sequential refinement of working memory representations

Despite the adaptative nature of working memory (WM) refinement (e.g. repulsion), a fundamental question remains unaddressed: what constitutes the unit of WM refinement? Specifically, does the refinement process apply to the entire object (object-based), specific features (feature-based), or potentially involve other mechanisms? Utilizing dual-feature objects and the continuous memory task, we examined whether the repulsion distortion induced in one feature (the trigger feature) could be transmitted to other features (the dependent feature) of the same object. Across one preliminary experiment and five formal experiments, we supported that the WM refinement is neither strictly object-based nor feature-based, but occurs dynamically and sequentially across distinct features. Specifically, the repulsion induced by the trigger feature was transmitted to the dependent feature only during extended maintenance periods, not during short maintenance. Our findings supported the dynamic sequential refinement of WM: refinement induced by a trigger feature could extend to other features, but this transmission is time-consuming.

Multiple item representations in visual working memory simultaneously guide attention

Visual working memory (VWM) is a subject of ongoing debate regarding whether multiple item representations can simultaneously guide attention. The Single Item Template hypothesis (SIT) posits that VWM representations only allow a single item to guide attention, while the Multiple Item Template hypothesis (MIT) suggests that multiple items in VWM representations can guide attention simultaneously. This study further investigates this through a dual-task paradigm. Participants were required to complete memory-search tasks under different memory and match types, with memory items and distractors being of the same category (Experiment 1) and different categories (Experiment 2). Results show: (1) In Experiment 1, when the memory type was color, multiple item representations in VWM simultaneously guided attention, providing support for the MIT hypothesis; however, when the memory type was graphic, multiple item representations in VWM did not simultaneously guide attention, providing support for the SIT hypothesis. (2) In Experiment 2, whether the memory type was color or graphic, multiple item representations in VWM did not simultaneously guide attention, providing support for the SIT hypothesis. Whether multiple item representations in VWM can simultaneously guide attention is significantly influenced by memory types and the relationship between memory items and categories of distractors.

The effects of aerobic exercise on goal-directed attention and inhibitory control in individuals with high trait anxiety: an EEG study

Anxiety is known to significantly impair cognitive function, particularly attentional control. While exercise has been demonstrated to alleviate these cognitive deficits, the precise neural mechanisms underlying these effects remain poorly understood. This study examines the effects of exercise on attentional control in individuals with high trait anxiety, based on attentional control theory, which suggests that such individuals have reduced top-down attention. Thirty-eight participants were randomly assigned to either an exercise group or a reading group. The exercise group engaged in 30 min of moderate-intensity cycling, while the reading group spent 30 min reading quietly. In Experiment 1, goal-directed attention was assessed using a cue-object paradigm, and in Experiment 2, inhibitory control was evaluated through a visual search task. EEG data indicated that the exercise group exhibited significantly larger Pd components in both experiments, suggesting enhanced attentional focus and improved inhibition of distractors. These findings suggest that aerobic exercise enhances top-down attentional processes, particularly goal-directed attention and distractor inhibition, offering potential as an intervention for individuals with high trait anxiety.

Long-term memory for distractors: Effects of involuntary attention from working memory

In a visual search task, attention to task-irrelevant distractors impedes search performance. However, is it maladaptive to future performance? Here, I showed that attended distractors in a visual search task were better remembered in long-term memory (LTM) in the subsequent surprise recognition task than non-attended distractors. In four experiments, participants performed a visual search task using real-world objects of a single color. They encoded color in working memory (WM) during the task; because each object had a different color, participants directed their attention to the WM-matching colored distractor. Then, in the surprise recognition task, participants were required to indicate whether an object had been shown in the earlier visual search task, regardless of its color. The results showed that attended distractors were remembered better in LTM than non-attended distractors (Experiments 1 and 2). Moreover, the more participants directed their attention to distractors, the better they explicitly remembered them. Participants did not explicitly remember the color of the attended distractors (Experiment 3) but remembered integrated information with object and color (Experiment 4). When the color of the distractors in the recognition task was mismatched with the color in the visual search task, LTM decreased compared to color-matching distractors. These results suggest that attention to distractors impairs search for a target but is helpful in remembering distractors in LTM. When task-irrelevant distractors become task-relevant information in the future, their attention becomes beneficial.

Top-down knowledge surpasses selection history in influencing attentional guidance

Visual attention is influenced by the characteristics of the stimuli (bottom-up), their task relevance (top-down), and prior experience (e.g., selection history and learning). However, it is largely unclear how learning and selection history interact with top-down attentional guidance. We combined trial-and-error learning with a spatial cueing protocol to test whether previously learned target-defining features continued to capture attention if participants were instructed to search for a new target feature (Experiment 1) or had to learn a new target feature (Experiment 2). It turned out that the previously learned feature quickly stopped capturing attention when the target feature changed (Experiment 1; even before participants learned the new target-defining feature, in Experiment 2). Finally, in Experiment 3, in which participants learned to search for targets defined by two redundant features (color and orientation), we found possible reasons for the dominance of the instructed feature over learning. Participants reported using only the target color for their search. Consequently, only cues with a target color captured attention. The unused target orientation only captured attention in participants aware of both target-defining features (13 out of 23) and only if the orientation was presented in the target color. We conclude that knowledge of target-defining features and their use as search criterion is critical for attentional guidance, while previously learned target features either influence attentional guidance only contingent on such deliberately selected top-down based attentional control settings or may influence visual search but not attentional guidance.

Negative cues minimize visual search specificity effects

Prior target knowledge (i.e., positive cues) improves visual search performance. However, there is considerable debate about whether distractor knowledge (i.e., negative cues) can guide search. Some studies suggest the active suppression of negatively cued search items, while others suggest the initial capture of attention by negatively cued items. Prior work has used pictorial or specific text cues but has not explicitly compared them. We build on that work by comparing positive and negative cues presented pictorially and as categorical text labels using photorealistic objects and eye movement measures. Search displays contained a target (cued on positive trials), a lure from the target category (cued on negative trials), and four categorically-unrelated distractors. Search performance with positive cues resulted in stronger attentional guidance and faster object recognition for pictorial relative to categorical cues (i.e., a pictorial advantage, suggesting specific visual details afforded by pictorial cues improved search). However, in most search performance metrics, negative cues mitigate the pictorial advantage. Given that the negatively cued items captured attention, generated target guidance but mitigated the pictorial advantage, these results are partly consistent with both existing theories. Specific visual details provided in positive cues produce a large pictorial advantage in all measures, whereas specific visual details in negative cues only produce a small pictorial advantage for object recognition but not for attentional guidance. This asymmetry in the pictorial advantage suggests that the down-weighting of specific negatively cued visual features is less efficient than the up-weighting of specific positively cued visual features.

The presence of a distractor matching the content of working memory induces delayed quitting in visual search

Previous research has shown that the presence of a distractor object matching the current content of working memory interacts with visual search. Because finding a target and quitting a search without finding a target may be implemented by qualitatively different processes, it is possible that the effects of a memory-matching distractor on target-present trials and on target-absent trials reveal different mechanisms by which the memory-matching distractor interacts with visual search. Although previous studies have well established the effect of attentional capture by a memory-matching distractor when the target object is found in the search display, there remains an open question about whether the presence of a memory-matching distractor can affect the process of search termination when no target is found. In the present study, we showed that search termination times on target-absent trials were delayed by the presence of a distractor matching the content of visual working memory. This delayed quitting effect cannot be conceived of as a more general influence of visual short-term memory, because the presence of a distractor matching the content of passive visual short-term memory (i.e., visual priming) did not influence quitting behavior in visual search. These findings offer a novel perspective that distractors matching the information maintained in visual working memory can cause observers to delay search termination when no target has been found.

Effects of visual search task on attentional bias and stress response under pressure

BACKGROUND

it has always been a problem for athletes that their performance is out of order due to pressure in major competitions. The change of attention pattern and the emergence of stress response (SR) caused by negative affect (NA) are the direct reasons for the greater impact on the performance of athletes. It is a hot topic to explore how to improve attention bias (AB) and SR of athletes in stressful situations.

OBJECTIVE

the study aimed to analyze the improvement effect of visual search task (VST) training on AB and SR of athletes under pressure situations.

METHODS

62 male basketball players with national level 2 or above of Shenyang sports institute were divided into experimental group (EG) and control group (CG). Visual search task training program was used in the EG (happy, sad, disgusted, neutral faces) and sham training program was used in the CG (all faces with neutral expression) for two months. Under the stress situation, attention behavior of all subjects before and after training was tested. Physiological coherence and autonomic balance system were used to record heart rate variability synchronously. Parallel frequency domain analysis was divided into very low frequency band (VLF), low frequency (LF), high frequency (HF) and total spectrum (TP). The normalized treatment obtained indexes such as HFnorm, LFnorm, and LF/HF. The e-prime 2.0 software was adopted to obtain the attention bias score. The Positive and Negative Affect Scale (PANAS) and the self-rating stress scale were adopted for evaluation before and after training.

RESULTS

the self-rating pressure in the two groups was lower than that before the training, and the pressure in the experimental group was lower than that in the control group (P < 0.05). After training, the positive emotion of the experimental group was higher than that of the control group, and the EG was lower than that of the CG (P < 0.05). After training, the score of attention bias of happy and neutral faces in the EG was higher than that of theCG, while the score of attention bias of sad and disgusted faces was lower than that of the CG (P < 0.05). After training, LF/HF and LFnorm in the EG were lower than those in the CG, and HFnorm was higher than those in the CG (P < 0.05).

CONCLUSIONS

the training of visual search task can effectively improve the athletes' PA and AB of positive information, reduce the attention bias of negative information and psychological pressure, and relieve theSR.

Allocation of resources in working memory: Theoretical and empirical implications for visual search

Recently, working memory (WM) has been conceptualized as a limited resource, distributed flexibly and strategically between an unlimited number of representations. In addition to improving the precision of representations in WM, the allocation of resources may also shape how these representations act as attentional templates to guide visual search. Here, we reviewed recent evidence in favor of this assumption and proposed three main principles that govern the relationship between WM resources and template-guided visual search. First, the allocation of resources to an attentional template has an effect on visual search, as it may improve the guidance of visual attention, facilitate target recognition, and/or protect the attentional template against interference. Second, the allocation of the largest amount of resources to a representation in WM is not sufficient to give this representation the status of attentional template and thus, the ability to guide visual search. Third, the representation obtaining the status of attentional template, whether at encoding or during maintenance, receives an amount of WM resources proportional to its relevance for visual search. Thus defined, the resource hypothesis of visual search constitutes a parsimonious and powerful framework, which provides new perspectives on previous debates and complements existing models of template-guided visual search.

Eye movements and the label feedback effect: Speaking modulates visual search via template integrity

The label-feedback hypothesis (Lupyan, 2012) proposes that language modulates low- and high-level visual processing, such as priming visual object perception. Lupyan and Swingley (2012) found that repeating target names facilitates visual search, resulting in shorter response times (RTs) and higher accuracy. In the present investigation, we conceptually replicated and extended their study, using additional control conditions and recording eye movements during search. Our goal was to evaluate whether self-directed speech influences target locating (i.e. attentional guidance) or object perception (i.e., distractor rejection and target appreciation). In three experiments, during object search, people spoke target names, nonwords, irrelevant (absent) object names, or irrelevant (present) object names (all within-participants). Experiments 1 and 2 examined search RTs and accuracy: Speaking target names improved performance, without differences among the remaining conditions. Experiment 3 incorporated eye-tracking: Gaze fixation patterns suggested that language does not affect attentional guidance, but instead affects both distractor rejection and target appreciation. When search trials were conditionalized according to distractor fixations, language effects became more orderly: Search was fastest while people spoke target names, followed in linear order by the nonword, distractor-absent, and distractor-present conditions. We suggest that language affects template maintenance during search, allowing fluent differentiation of targets and distractors. Materials, data, and analyses can be retrieved here: https://osf.io/z9ex2/.

Memory-driven capture occurs for individual features of an object

Items held in working memory (WM) capture attention (memory-driven capture). People can selectively prioritize specific object features in WM. Here, we examined whether feature-specific prioritization within WM modulates memory-driven capture. In Experiment 1, after remembering the color and orientation of a triangle, participants were instructed, via retro-cue, whether the color, the orientation, or both features were relevant. To measure capture, we asked participants to execute a subsequent search task, and we compared performance in displays that did and did not contain the memory-matching feature. Color attracted attention only when it was relevant. No capture by orientation was found. In Experiment 2, we presented the retro-cue at one of the four locations of the search display to direct attention to specific objects. We found capture by color and this capture was larger when it was indicated as relevant. Crucially, orientation also attracted attention, but only when it was relevant. These findings provide evidence for reciprocal interaction between internal prioritization and external attention on the features level. Specifically, internal feature-specific prioritization modulates memory-driven capture but this capture also depends on the salience of the features.

Oculomotor capture by search-irrelevant features in visual working memory: on the crucial role of target-distractor similarity

When searching for varying targets in the environment, a target template has to be maintained in visual working memory (VWM). Recently, we showed that search-irrelevant features of a VWM template bias attention in an object-based manner, so that objects sharing such features with a VWM template capture the eyes involuntarily. Here, we investigated whether target-distractor similarity modulates capture strength. Participants saccaded to a target accompanied by a distractor. A single feature (e.g., shape) defined the target in each trial indicated by a cue, and the cue also varied in one irrelevant feature (e.g., color). The distractor matched the cue's irrelevant feature in half of the trials. Nine experiments showed that target-distractor similarity consistently influenced the degree of oculomotor capture. High target-distractor dissimilarity in the search-relevant feature reduced capture by the irrelevant feature (Experiments 1, 3, 6, 7). However, capture was reduced by high target-distractor similarity in the search-irrelevant feature (Experiments 1, 4, 5, 8). Strong oculomotor capture was observed if target-distractor similarity was reasonably low in the relevant and high in the irrelevant feature, irrespective of whether color or shape were relevant (Experiments 2 and 5). These findings argue for involuntary and object-based, top-down control by VWM templates, whereas its manifestation in oculomotor capture depends crucially on target-distractor similarity in relevant and irrelevant feature dimensions of the search object.

Visual working memory modulates the temporal resolution of visual perception

The present study examined how visual working memory affects temporal resolution of visual stimuli that match the memorised nontemporal information about stimulus features (e.g., shapes). The results show that active maintenance of a sample shape in visual working memory impaired the concurrent detection of a sufficiently brief temporal gap within a matching visual target stimulus. The impairment of temporal gap detection was not likely due to the mechanism of visual priming from the presentation of the sample shape, because there was no evidence for priming effects when the sample was only passively viewed without working memory demands or when the sample was initially encoded into memory but did not need to be actively maintained in mind by the time the target stimulus appeared. These findings demonstrate that visual working memory can lower the temporal resolution of visual perception and thereby impair performance in the temporal gap detection task that requires fine temporal segregation of visual information, and they suggest the existence of a previously unknown downside to the interplay between working memory and visual perception.

Object-based grouping benefits without integrated feature representations in visual working memory

Visual working memory (VWM) is typically considered to represent complete objects—that is, separate parts of an object are maintained as bound objects. Yet it remains unclear whether and how the features of disparate parts are integrated into a whole-object memory representation. Using a change detection paradigm, the present study investigated whether VWM performance varies as a function of grouping strength for features that either determine the grouped object (orientation) or that are not directly grouping relevant (color). Our results showed a large grouping benefit for grouping-relevant orientation features and, additionally, a much smaller, albeit reliable, benefit for grouping-irrelevant color features when both were potentially task relevant. By contrast, when color was the only task-relevant feature, no grouping benefit from the orientation feature was revealed both under lower or relatively high demands for precision. Together, these results indicate that different features of an object are stored independently in VWM; and an emerging, higher-order grouping structure does not automatically lead to an integrated representation of all available features of an object. Instead, an object benefit depends on the specific task demands, which may generate a linked, task-dependent representation of independent features.

Bottom-up perceptual salience and top-down retro-cues concurrently determine state in visual working memory

Recent studies have demonstrated that in visual working memory (VWM), only items in an active state can guide attention. Further evidence has revealed that items with higher perceptual salience or items prioritised by a valid retro-cue in VWM tend to be in an active state. However, it is unclear which factor (perceptual salience or retro-cues) is more important for influencing the item state in VWM or whether the factors can act concurrently. Experiment 1 examined the role of perceptual salience by asking participants to hold two features with relatively different perceptual salience (colour vs. shape) in VWM while completing a visual search task. Guidance effects were found when either colour or both colour and shape in VWM matched one of the search distractors but not when shape matched. This demonstrated that the more salient feature in VWM can actively guide attention, while the less salient feature cannot. However, when shape in VWM was cued to be more relevant (prioritised) in Experiment 2, we found guidance effects in both colour-match and shape-match conditions. That is, both more salient but non-cued colour and less salient but cued shape could be active in VWM, such that attentional selection was affected by the matching colour or shape in the visual search task. This suggests that bottom-up perceptual salience and top-down retro-cues can jointly determine the active state in VWM.

Object features reinstated from episodic memory guide attentional selection

When observers search for an object in the environment, they compare the incoming sensory information to the attentional template, a representation of the target in visual working memory (VWM). Previous studies have shown that visual search is more efficient when the attentional template is precise. We pursued the hypothesis that the attentional template in VWM is automatically complemented by features from long-term memory, possibly to increase its precision. At the beginning of the experiment, observers learned associations between shape and color. Then, we tested whether selecting one of these shapes was influenced by the previously associated color. To this end, we ran a saccadic selection task consisting of a memory and choice display. In the memory display, the target shape was presented at central fixation and participants were instructed to foveate this shape in the subsequent choice display. In the choice display, the target shape appeared together with a distractor shape at eccentric positions. Importantly, the target shape was colorless (gray) in the memory display so that only shape, but not color was loaded into VWM. However, saccades went more frequently to the target shape when it was shown in the learned color than when this color was shown in the distractor. Thus, the color of the target shape was reinstated from episodic memory to complement the attentional template in VWM.

Feature-based guidance of attention during post-saccadic selection

Current models of trans-saccadic perception propose that, after a saccade, the saccade target object must be localized among objects near the landing position. However, the nature of the attentional mechanisms supporting this process is currently under debate. In the present study, we tested whether surface properties of the saccade target object automatically bias post-saccadic selection using a variant of the visual search task. Participants executed a saccade to a shape-singleton target in a circular array. During this primary saccade, the array sometimes rotated so that the eyes landed between the target and an adjacent distractor, requiring gaze correction. In addition, each object in the array had an incidental color value. On Switch trials, the target and adjacent distractor switched colors. The accuracy and latency of gaze correction to the target (measures that provide a direct index of target localization) were compared with a control condition in which no color switch occurred (No-switch trials). Gaze correction to the target was substantially impaired in the Switch condition. This result was obtained even when participants had substantial incentive to avoid encoding the color of the saccade target. In addition, similar effects were observed when the roles of the two feature dimensions (color and shape) were reversed. The results indicate that saccade target features are automatically encoded before a saccade, are retained in visual working memory across the saccade, and instantiate a feature-based selection operation when the eyes land, biasing attention toward objects that match target features.

The contents of visual working memory delay the perceived offset of matching visual stimuli

Previous research suggests that the perception of stimulus onset can be accelerated by a match between the contents of visual working memory and the stimulus presented alone in the peripheral visual field. This onset acceleration effect might contribute to previously reported effects of working memory on perceived stimulus duration. However, it remains possible that the contents of visual working memory may also modulate the offset perception of matching visual stimuli, thereby contributing to the modulation of duration perception by working memory. The present study directly tested this possibility by using a simple reaction time task to assess the effect of visual working memory on perceived stimulus offset. Participants were asked to maintain a sample stimulus in working memory and subsequently had to respond to the offset of a single visual target. Across three experiments, we showed that the offset response was reliably slower when the target matched the sample held in visual working memory, as compared with when the target did not. This effect was not likely attributed to the mechanism of repetition priming from the presentation of the sample, because we failed to observe a priming effect either when the sample was only passively viewed without working memory demands or when the sample was initially encoded into memory but did not need to be actively maintained in mind by the time the offset target appeared. The findings provide direct evidence indicating that active maintenance of information in visual working memory delays the perceived offset of matching visual stimuli.

Task-Irrelevant Features in Visual Working Memory Influence Covert Attention: Evidence from a Partial Report Task

Selecting a target based on a representation in visual working memory (VWM) affords biasing covert attention towards objects with memory-matching features. Recently, we showed that even task-irrelevant features of a VWM template bias attention. Specifically, when participants had to saccade to a cued shape, distractors sharing the cue's search-irrelevant color captured the eyes. While a saccade always aims at one target location, multiple locations can be attended covertly. Here, we investigated whether covert attention is captured similarly as the eyes. In our partial report task, each trial started with a shape-defined search cue, followed by a fixation cross. Next, two colored shapes, each including a letter, appeared left and right from fixation, followed by masks. The letter inside that shape matching the preceding cue had to be reported. In Experiment 1, either target, distractor, both, or no object matched the cue's irrelevant color. Target-letter reports were most frequent in target-match trials and least frequent in distractor-match trials. Irrelevant cue and target color never matched in Experiment 2. Still, participants reported the distractor more often to the target's disadvantage, when cue and distractor color matched. Thus, irrelevant features of a VWM template can influence covert attention in an involuntarily object-based manner when searching for trial-wise varying targets.

Working Memory and Attention - A Conceptual Analysis and Review

There is broad agreement that working memory is closely related to attention. This article delineates several theoretical options for conceptualizing this link, and evaluates their viability in light of their theoretical implications and the empirical support they received. A first divide exists between the concept of attention as a limited resource, and the concept of attention as selective information processing. Theories conceptualizing attention as a resource assume that this resource is responsible for the limited capacity of working memory. Three versions of this idea have been proposed: Attention as a resource for storage and processing, a shared resource for perceptual attention and memory maintenance, and a resource for the control of attention. The first of these three is empirically well supported, but the other two are not. By contrast, when attention is understood as a selection mechanism, it is usually not invoked to explain the capacity limit of working memory - rather, researchers ask how different forms of attention interact with working memory, in two areas. The first pertains to attentional selection of the contents of working memory, controlled by mechanisms of filtering out irrelevant stimuli, and removing no-longer relevant representations from working memory. Within working memory contents, a single item is often selected into the focus of attention for processing. The second area pertains to the role of working memory in cognitive control. Working memory contributes to controlling perceptual attention - by holding templates for targets of perceptual selection - and controlling action - by holding task sets to implement our current goals.

Task-dependent effects of voluntary space-based and involuntary feature-based attention on visual working memory

Previous research has shown that visual working memory (VWM) can be modulated by space-based or feature-based attentional selection. However, it remains unclear how the two modes of attention operate jointly to affect VWM, and in particular, if involuntary feature-based attention plays a role in VWM. In this study, a pre-cued change detection paradigm was employed to investigate the concurrent effects of space- and feature-based attention on VWM. Space-based attention was manipulated by informative spatial cueing and by varying the proximity between the test item and the cued (fixated) memory item, while feature-based attention was induced in an involuntary manner by having the test item to share the same color or shape with the cued item on a fraction of trials. The results showed that: (1) the memory performance for the cued items was always better than the uncued items, suggesting a beneficial effect of voluntary spatial attention; (2) with a brief duration of the memory array (250 ms), cue-test proximity benefited VWM in the shape judgment task but not in the color judgment task, whereas with a longer duration (1200 ms), no proximity effect was found for either task; (3) VWM was improved for the same-colored items regardless of the task and duration; (4) VWM was improved for the same-shaped items only in the shape judgment task with the longer duration of the memory array. A discrimination task further showed that the proximity effect associated with VWM reflects a perceptual bottleneck in memory encoding for shape but not for color with a brief display. Our results suggest that involuntary feature-based attention could be triggered by spatial cueing to modulate VWM; involuntary color-based attention facilitates VWM independently of task, whereas shape-based facilitation is task-dependent, i.e., confined only to the shape judgment task, presumably reflecting different attention-guiding potencies of the two features.

The precision of attentional selection is far worse than the precision of the underlying memory representation

Voluntary attentional selection requires the match of sensory input to a stored representation of the target features. We compared the precision of attentional selection to the precision of the underlying memory representation of the target. To measure the precision of attentional selection, we used a cue-target paradigm where participants searched for a colored target. Typically, RTs are shorter at the cued compared to uncued locations when the cue has the same color as the target. In contrast, cueing effects are absent or even inverted when cue and target colors are dissimilar. By systematically varying the difference between cue and target color, we calculated a function relating cue color to cueing effects. The width of this function reflects the precision of attentional selection and was compared to the precision of judgments of the target color on a color wheel. The precision of the memory representation was far better than the precision of attentional selection. When the task was made more difficult by increasing the similarity between the target and the nontarget stimuli in the target display, the precision of attentional selection increased, but was still worse than the precision of memory. When the search task was made more difficult, we also observed that for dissimilar cue colors, RTs were slower at cued than at uncued locations (i.e., same location costs), suggesting that improvements in attentional selectivity were achieved by suppressing non-target colors.

Multiple representations in visual working memory simultaneously guide attention: The type of memory-matching representation matters

Whether multiple visual working memory (VWM) representations can simultaneously become active templates to guide attention is controversial. The single-item-template hypothesis argues that only one VWM representation can be active at a time, whereas the multiple-item-template hypothesis argues that multiple VWM templates can simultaneously guide attention. The present study examined the two hypotheses in three (out of four) experiments, using three different types of memory objects: Experiment 1: shapes; Experiment 2: colors; and Experiment 3: colored shapes. Participants were required to hold one (memory-1) or two objects (memory-2) in VWM while performing a tilted line search task. Zero (match-0), one (match-1), or two (match-2) memory stimuli reappeared as distractors in the search array. Guidance effects were found for each type of memory stimuli. More importantly, the guidance effect for memory-2/match-2 trials was significantly larger than that for memory-2/match-1 and memory-1/match-1 trials when holding two colors or two colored shapes in VWM, which is in line with the multiple-item-template hypothesis. However, the pattern of simultaneous guidance effect is not perfectly found for two memory shapes, which may indicate that a reliable simultaneous guidance effect from two representations in VWM can be observed only when the memory-matching stimuli is more effective in guiding attention. Experiment 4 directly compared the guidance effect induced by feature-based matches (partial matching) with the guidance effect induced object-based matches (complete matching) in memory-set-size 2. Reliable guidance effects in match-1 and match-2 trials for object-based matches but not for feature-based matches confirmed the crucial role of the type of memory-matching stimuli in guiding attention.

Learned feature variance is encoded in the target template and drives visual search

Real world visual search targets are frequently imperfect perceptual matches to our internal target templates. For example, the same friend on different occasions is likely to wear different clothes, hairstyles, and accessories, but some of these may be more likely to vary than others. The ability to deal with template-to-target variability is important to visual search in natural environments, but we know relatively little about how feature variability is handled by the attentional system. In these studies, we test the hypothesis that top-down attentional biases are sensitive to the variance of target feature dimensions over time and prioritize information from less-variable dimensions. On each trial, subjects were shown a target cue composed of colored dots moving in a specific direction followed by a working memory probe (30%) or visual search display (70%). Critically, the target features in the visual search display differed from the cue, with one feature drawn from a distribution narrowly centered over the cued feature (low-variance dimension), and the other sampled from a broader distribution (high-variance dimension). The results demonstrate that subjects used knowledge of the likely cue-to-target variance to set template precision and bias attentional selection. Moreover, an individual's working memory precision for each feature predicted search performance. Our results suggest that observers are sensitive to the variance of feature dimensions within a target and use this information to weight mechanisms of attentional selection.

Hide and seek: Directing top-down attention is not sufficient for accelerating conscious access

At any moment in time, we have a single conscious visual experience representing a minute part of our visual world. As such, the visual input stimulating our retinae is in continuous competition for reaching conscious access. Many complex cognitive operations can only be applied to consciously accessible visual information, thereby raising the question whether humans have the ability to select which parts of their visual input reaches consciousness. Top-down attention allows humans to flexibly assign more processing resources to certain parts of our visual input, making it a likely mechanism to volitionally bias conscious access. Here, we investigated whether directing top-down attention to a particular location or feature accelerates conscious access of an initially suppressed visual stimulus at the attended location, or of the attended feature. We instructed participants to attend a spatial location (Experiment 1) or color (Experiment 2) for a speeded discrimination task, using a highly predictive cue. The predictive cues were highly effective in prompting sustained attention towards the cued location or color, as evidenced by faster discrimination of cued relative to uncued targets. We simultaneously measured detection times to interocularly suppressed probes that were either of the cued (i.e., attended) color/location or not, and were visually distinct from the targets used for the discrimination task. Despite our successful manipulation of top-down attention, suppressed probes were not released from suppression faster when they were presented at the attended location, or in the attended color. In contrast, when observers were cued to attend a color for locating targets of an ill-defined shape (inciting a broader attentional template), we did observe faster conscious access of probes in the attended color (Experiment 3). We discuss our findings in light of the specificity of attentional templates, and the inherent limitations that this poses for top-down attentional biases on conscious access.