Conceptual information of meaningful objects is stored incidentally.

Prior research has shown that visual working memory capacity is enhanced for meaningful stimuli (i.e., real-world objects) compared to abstract shapes (i.e., colored circles). Here, we hypothesized that the shape of meaningful objects would be better remembered incidentally than the shape of nonmeaningful objects in a color memory task where the shape of the objects is task-irrelevant. We used a surprise-trial paradigm in which participants performed a color memory task for several trials before being probed with a surprise trial that asked them about the shape of the last object they saw. Across three experiments, we found a memory advantage for recognizable shapes relative to scrambled versions of these shapes (Experiment 1) that was robust across different encoding times (Experiment 2), and the addition of a verbal suppression task (Experiment 3). Interestingly, this advantage disappeared when all objects were from the same category (Experiment 4), suggesting that people are incidentally encoding broad conceptual information about object identities, but not visual details. Finally, when we asked about the location of objects in a surprise trial, we did not observe any difference between the two stimulus types (Experiment 5). Overall, these results show that conceptual information about the categories of meaningful objects is incidentally encoded into working memory even when task-irrelevant. This privilege for meaningful information does not exhibit a trade-off with location memory, suggesting that meaningful features influence representations of visual working memory in higher-level visual regions without altering the use of spatial reference frames at the lower level. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Attention to object categories: Selection history determines the breadth of attentional tuning during real-world object search.

People excel at learning the statistics of their environments. For instance, people rapidly learn to pay attention to locations that frequently contain visual search targets. Here, we investigated how frequently finding specific objects as search targets influences attentional selection during real-world object search. We investigated how learning that a specific object (e.g., a coat) is task-relevant affects searching for that object and whether a previously frequent target would influence search more broadly for all items of that target's category (e.g., all coats). Across five experiments, one or more objects from a single category were likely targets during a training phase, after which objects from many categories became equally likely to be targets in a neutral testing phase. Participants learned to find a single frequent target object faster than other objects (Experiment 1, N = 44). This learning was specific to that object, with no advantage in finding a novel category-matched object (Experiment 2, N = 32). In contrast, learning to prioritize multiple exemplars from one category spread to untrained objects from the same category, and this spread was comparable whether participants learned to find two, four, or six exemplars (Experiment 3, N = 72). These differences in the breadth of attention were due to variability in the learning environment and not differences in task (Experiment 4, N = 24). Finally, a set-size manipulation showed that learning affects attentional guidance itself, not only postselective processing (Experiment 5, N = 96). These experiments demonstrate that the breadth of attentional tuning is flexibly adjusted based on recent experience to effectively address task demands. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Representational structures as a unifying framework for attention.

Our visual system consciously processes only a subset of the incoming information. Selective attention allows us to prioritize relevant inputs, and can be allocated to features, locations, and objects. Recent advances in feature-based attention suggest that several selection principles are shared across these domains and that many differences between the effects of attention on perceptual processing can be explained by differences in the underlying representational structures. Moving forward, it can thus be useful to assess how attention changes the structure of the representational spaces over which it operates, which include the spatial organization, feature maps, and object-based coding in visual cortex. This will ultimately add to our understanding of how attention changes the flow of visual information processing more broadly.

Sequential encoding aids working memory for meaningful objects' identities but not for their colors.

Previous studies have found that real-world objects' identities are better remembered than simple features like colored circles, and this effect is particularly pronounced when these stimuli are encoded one by one in a serial, item-based way. Recent work has also demonstrated that memory for simple features like color is improved if these colors are part of real-world objects, suggesting that meaningful objects can serve as a robust memory scaffold for their associated low-level features. However, it is unclear whether the improved color memory that arises from the colors appearing on real-world objects is affected by encoding format, in particular whether items are encoded sequentially or simultaneously. We test this using randomly colored silhouettes of recognizable versus unrecognizable scrambled objects that offer a uniquely controlled set of stimuli to test color working memory of meaningful versus non-meaningful objects. Participants were presented with four stimuli (silhouettes of objects or scrambled shapes) simultaneously or sequentially. After a short delay, they reported either which colors or which shapes they saw in a two-alternative forced-choice task. We replicated previous findings that meaningful stimuli boost working memory performance for colors (Exp. 1). We found that when participants remembered the colors (Exp. 2) there was no difference in performance across the two encoding formats. However, when participants remembered the shapes and thus identity of the objects (Exp. 3), sequential presentation resulted in better performance than simultaneous presentation. Overall, these results show that different encoding formats can flexibly impact visual working memory depending on what the memory-relevant feature is.

Comparing memory capacity across stimuli requires maximally dissimilar foils: Using deep convolutional neural networks to understand visual working memory capacity for real-world objects.

The capacity of visual working and visual long-term memory plays a critical role in theories of cognitive architecture and the relationship between memory and other cognitive systems. Here, we argue that before asking the question of how capacity varies across different stimuli or what the upper bound of capacity is for a given memory system, it is necessary to establish a methodology that allows a fair comparison between distinct stimulus sets and conditions. One of the most important factors determining performance in a memory task is target/foil dissimilarity. We argue that only by maximizing the dissimilarity of the target and foil in each stimulus set can we provide a fair basis for memory comparisons between stimuli. In the current work we focus on a way to pick such foils objectively for complex, meaningful real-world objects by using deep convolutional neural networks, and we validate this using both memory tests and similarity metrics. Using this method, we then provide evidence that there is a greater capacity for real-world objects relative to simple colors in visual working memory; critically, we also show that this difference can be reduced or eliminated when non-comparable foils are used, potentially explaining why previous work has not always found such a difference. Our study thus demonstrates that working memory capacity depends on the type of information that is remembered and that assessing capacity depends critically on foil dissimilarity, especially when comparing memory performance and other cognitive systems across different stimulus sets.

Dissociable Neural Mechanisms Underlie the Effects of Attention on Visual Appearance and Response Bias.

A prominent theoretical framework spanning philosophy, psychology, and neuroscience holds that selective attention penetrates early stages of perceptual processing to alter the subjective visual experience of behaviorally relevant stimuli. For example, searching for a red apple at the grocery store might make the relevant color appear brighter and more saturated compared with seeing the exact same red apple while searching for a yellow banana. In contrast, recent proposals argue that data supporting attention-related changes in appearance reflect decision- and motor-level response biases without concurrent changes in perceptual experience. Here, we tested these accounts by evaluating attentional modulations of EEG responses recorded from male and female human subjects while they compared the perceived contrast of attended and unattended visual stimuli rendered at different levels of physical contrast. We found that attention enhanced the amplitude of the P1 component, an early evoked potential measured over visual cortex. A linking model based on signal detection theory suggests that response gain modulations of the P1 component track attention-induced changes in perceived contrast as measured with behavior. In contrast, attentional cues induced changes in the baseline amplitude of posterior alpha band oscillations (∼9-12 Hz), an effect that best accounts for cue-induced response biases, particularly when no stimuli are presented or when competing stimuli are similar and decisional uncertainty is high. The observation of dissociable neural markers that are linked to changes in subjective appearance and response bias supports a more unified theoretical account and demonstrates an approach to isolate subjective aspects of selective information processing.SIGNIFICANCE STATEMENT Does attention alter visual appearance, or does it simply induce response bias? In the present study, we examined these competing accounts using EEG and linking models based on signal detection theory. We found that response gain modulations of the visually evoked P1 component best accounted for attention-induced changes in visual appearance. In contrast, cue-induced baseline shifts in alpha band activity better explained response biases. Together, these results suggest that attention concurrently impacts visual appearance and response bias, and that these processes can be experimentally isolated.

Contextual and Temporal Constraints for Attentional Capture: Commentary on Theeuwes' 2023 Review "The Attentional Capture Debate: When Can We Avoid Salient Distractors and when Not?"

Salient distractors demand our attention. Their salience, derived from intensity, relative contrast or learned relevance, captures our limited information capacity. This is typically an adaptive response as salient stimuli may require an immediate change in behaviour. However, sometimes apparent salient distractors do not capture attention. Theeuwes, in his recent commentary, has proposed certain boundary conditions of the visual scene that result in one of two search modes, serial or parallel, that determine whether we can avoid salient distractors or not. Here, we argue that a more complete theory should consider the temporal and contextual factors that influence the very salience of the distractor itself.

No Fixed Limit for Storing Simple Visual Features: Realistic Objects Provide an Efficient Scaffold for Holding Features in Mind.

Prominent theories of visual working memory postulate that the capacity to maintain a particular visual feature is fixed. In contrast to these theories, recent studies have demonstrated that meaningful objects are better remembered than simple, nonmeaningful stimuli. Here, we tested whether this is solely because meaningful stimuli can recruit additional features-and thus more storage capacity-or whether simple visual features that are not themselves meaningful can also benefit from being part of a meaningful object. Across five experiments (30 young adults each), we demonstrated that visual working memory capacity for color is greater when colors are part of recognizable real-world objects compared with unrecognizable objects. Our results indicate that meaningful stimuli provide a potent scaffold to help maintain simple visual feature information, possibly because they effectively increase the objects' distinctiveness from each other and reduce interference.

Unveiling the time course of visual stabilization through human electrophysiology.

Object positions are coded relative to their surroundings, presumably providing visual stability during eye movements. But when does this perceived stability arise? Here we used a visual illusion, the frame-induced position shift, and measured electrophysiological activity elicited by an object whose perceived position was either shifted because of a surrounding frame or not, thus dissociating perceived and physical locations. We found that visually evoked responses were sensitive to only physical location earlier in time (∼70 ms), but both physical and illusory location information was present at a later time point (∼140 ms). Furthermore, location information could be reliably decoded across physical and illusory locations during the later time interval but not during the earlier time interval, demonstrating that neural activity patterns are shared between the two processes at a later stage. These results suggest that visual stability of objects emerges relatively late and is thus dependent on recurrent feedback from higher processing stages.

Feature-based attention warps the perception of visual features.

Selective attention improves sensory processing of relevant information but can also impact the quality of perception. For example, attention increases visual discrimination performance and at the same time boosts apparent stimulus contrast of attended relative to unattended stimuli. Can attention also lead to perceptual distortions of visual representations? Optimal tuning accounts of attention suggest that processing is biased towards "off-tuned" features to maximize the signal-to-noise ratio in favor of the target, especially when targets and distractors are confusable. Here, we tested whether such tuning gives rise to phenomenological changes of visual features. We instructed participants to select a color among other colors in a visual search display and subsequently asked them to judge the appearance of the target color in a 2-alternative forced choice task. Participants consistently judged the target color to appear more dissimilar from the distractor color in feature space. Critically, the magnitude of these perceptual biases varied systematically with the similarity between target and distractor colors during search, indicating that attentional tuning quickly adapts to current task demands. In control experiments we rule out possible non-attentional explanations such as color contrast or memory effects. Overall, our results demonstrate that selective attention warps the representational geometry of color space, resulting in profound perceptual changes across large swaths of feature space. Broadly, these results indicate that efficient attentional selection can come at a perceptual cost by distorting our sensory experience.

Distractor ignoring is as effective as target enhancement when incidentally learned but not when explicitly cued.

Explicit knowledge about upcoming target or distractor features can increase performance in tasks like visual search. However, explicit distractor cues generally result in smaller performance benefits than target cues, suggesting that suppressing irrelevant information is less effective than enhancing relevant information. Is this asymmetry a general principle of feature-based attention? Across four experiments (N = 75 each) we compared the efficiency of target selection and distractor ignoring through either incidental experience or explicit instructions. Participants searched for an orientation-defined target amidst seven distractors-three in the target color and four in another color. In Experiment 1, either targets (Exp. 1a) or distractors (Exp. 1b) were presented more often in a specific color than other possible search colors. Response times showed comparable benefits of learned attention towards (Exp. 1a) and away from (Exp. 1b) the frequent color, suggesting that learned target selection and distractor ignoring can be equally effective. In Experiment 2, participants completed a nearly identical task, only with explicit cues to the target (Exp. 2a) or distractor color (Exp. 2b), inducing voluntary attention. Both target and distractor cues were beneficial for search performance, but distractor cues much less so than target cues, consistent with previous results. Cross-experiment analyses verified that the relative inefficiency of distractor ignoring versus target selection is a unique characteristic of voluntary attention that is not shared by incidentally learned attention, pointing to dissociable mechanisms of voluntary and learned attention to support distractor ignoring.

Simulating the low-temperature, metastable electrochromism of Photosystem I: Applications to Thermosynechococcus vulcanus and Chroococcidiopsis thermalis.

Low-temperature, metastable electrochromism has been used as a tool to assign pigments in Photosystem I (PS I) from Thermosynechococcus vulcanus and both the white light and far-red light (FRL) forms of Chroococcidiopsis thermalis. We find that a minimum of seven pigments is required to satisfactorily model the electrochromism of PS I. Using our model, we provide a short list of candidates for the chlorophyll f pigment in FRL C. thermalis that absorbs at 756 nm, whose identity, to date, has proven to be controversial. Specifically, we propose the linker pigments A40 and B39 and two antenna pigments A26 and B24 as defined by crystal structure 1JB0. The pros and cons of these assignments are discussed, and we propose further experiments to better understand the functioning of FRL C. thermalis.

What You See Is What You Hear: Sounds Alter the Contents of Visual Perception.

Visual object recognition is not performed in isolation but depends on prior knowledge and context. Here, we found that auditory context plays a critical role in visual object perception. Using a psychophysical task in which naturalistic sounds were paired with noisy visual inputs, we demonstrated across two experiments (young adults; ns = 18-40 in Experiments 1 and 2, respectively) that the representations of ambiguous visual objects were shifted toward the visual features of an object that were related to the incidental sound. In a series of control experiments, we found that these effects were not driven by decision or response biases (ns = 40-85) nor were they due to top-down expectations (n = 40). Instead, these effects were driven by the continuous integration of audiovisual inputs during perception itself. Together, our results demonstrate that the perceptual experience of visual objects is directly shaped by naturalistic auditory context, which provides independent and diagnostic information about the visual world.

Feature similarity is non-linearly related to attentional selection: Evidence from visual search and sustained attention tasks.

Although many theories of attention highlight the importance of similarity between target and distractor items for selection, few studies have directly quantified the function underlying this relationship. Across two commonly used tasks-visual search and sustained attention-we investigated how target-distractor similarity impacts feature-based attentional selection. Importantly, we found comparable patterns of performance in both visual search and sustained feature-based attention tasks, with performance (response times and d', respectively) plateauing at medium target-distractor distances (40°-50° around a luminance-matched color wheel). In contrast, visual search efficiency, as measured by search slopes, was affected by a much more narrow range of similarity levels (10°-20°). We assessed the relationship between target-distractor similarity and attentional performance using both a stimulus-based and psychologically-based measure of similarity and found this nonlinear relationship in both cases. However, psychological similarity accounted for some of the nonlinearities observed in the data, suggesting that measures of psychological similarity are more appropriate when studying effects of target-distractor similarities. These findings place novel constraints on models of selective attention and emphasize the importance of considering the similarity structure of the feature space over which attention operates. Broadly, the nonlinear effects of similarity on attention are consistent with accounts that propose attention exaggerates the distance between competing representations, possibly through enhancement of off-tuned neurons.

Ten simple rules to study distractor suppression.

Distractor suppression refers to the ability to filter out distracting and task-irrelevant information. Distractor suppression is essential for survival and considered a key aspect of selective attention. Despite the recent and rapidly evolving literature on distractor suppression, we still know little about how the brain suppresses distracting information. What limits progress is that we lack mutually agreed upon principles of how to study the neural basis of distractor suppression and its manifestation in behavior. Here, we offer ten simple rules that we believe are fundamental when investigating distractor suppression. We provide guidelines on how to design conclusive experiments on distractor suppression (Rules 1-3), discuss different types of distractor suppression that need to be distinguished (Rules 4-6), and provide an overview of models of distractor suppression and considerations of how to evaluate distractor suppression statistically (Rules 7-10). Together, these rules provide a concise and comprehensive synopsis of promising advances in the field of distractor suppression. Following these rules will propel research on distractor suppression in important ways, not only by highlighting prominent issues to both new and more advanced researchers in the field, but also by facilitating communication between sub-disciplines.

No evidence for proactive suppression of explicitly cued distractor features.

Visual search benefits from advance knowledge of nontarget features. However, it is unknown whether these negatively cued features are suppressed in advance (proactively) or during search (reactively). To test this, we presented color cues varying from trial-to-trial that predicted target or nontarget colors. Experiment 1 (N = 96) showed that both target and nontarget cues speeded search. To test whether attention proactively modified cued feature representations, in Experiment 2 (N = 200), we interleaved color probe and search trials and had participants detect the color of a briefly presented ring that could either match the cued color or not. People detected positively cued colors better than other colors, whereas negatively cued colors were detected no better or worse than other colors. These results demonstrate that nontarget features are not suppressed proactively, and instead suggest that anticipated nontarget features are ignored via reactive mechanisms.

Guidance of attention by working memory is a matter of representational fidelity.

Items that are held in visual working memory can guide attention toward matching features in the environment. Predominant theories propose that to guide attention, a memory item must be internally prioritized and given a special template status, which builds on the assumption that there are qualitatively distinct states in working memory. Here, we propose that no distinct states in working memory are necessary to explain why some items guide attention and others do not. Instead, we propose variations in attentional guidance arise because individual memories naturally vary in their representational fidelity, and only highly accurate memories automatically guide attention. Across a series of experiments and a simulation we show that (a) items in working memory vary naturally in representational fidelity; (b) attention is guided by all well-represented items, though frequently only one item is represented well enough to guide; and (c) no special working memory state for prioritized items is necessary to explain guidance. These findings challenge current models of attentional guidance and working memory and instead support a simpler account for how working memory and attention interact: Only the representational fidelity of memories, which varies naturally between items, determines whether and how strongly a memory representation guides attention. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The role of meaning in visual working memory: Real-world objects, but not simple features, benefit from deeper processing.

Visual working memory is a capacity-limited cognitive system used to actively store and manipulate visual information. Visual working memory capacity is not fixed, but varies by stimulus type: Stimuli that are more meaningful are better remembered. In the current work, we investigate what conditions lead to the strongest benefits for meaningful stimuli. We propose that in some situations participants may try to encode the entire display holistically (i.e., in a quick "snapshot"). This may lead them to treat objects as simply meaningless, colored "blobs", rather than individually and in a high-level way, which could reduce benefits of meaningful stimuli. In a series of experiments, we directly test whether real-world objects, colors, perceptually matched less-meaningful objects, and fully scrambled objects benefit from deeper processing. We systematically vary the presentation format of stimuli at encoding to be either simultaneous-encouraging a parallel, "take-a-quick-snapshot" strategy-or present the stimuli sequentially, promoting a serial, each-item-at-once strategy. We find large advantages for meaningful objects in all conditions, but find that real-world objects-and to a lesser degree lightly scrambled, still meaningful versions of the objects-benefit from the sequential encoding and thus deeper, focused-on-individual-items processing, while colors do not. Our results suggest single-feature objects may be an outlier in their affordance of parallel, quick processing, and that in more realistic memory situations, visual working memory likely relies upon representations resulting from in-depth processing of objects (e.g., in higher-level visual areas) rather than solely being represented in terms of their low-level features. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Expectations about dynamic visual objects facilitates early sensory processing of congruent sounds.

The perception of a moving object can lead to the expectation of its sound, yet little is known about how visual expectations influence auditory processing. We examined how visual perception of an object moving continuously across the visual field influences early auditory processing of a sound that occurred congruently or incongruently with the object's motion. In Experiment 1, electroencephalogram (EEG) activity was recorded from adults who passively viewed a ball that appeared either on the left or right boundary of a display and continuously traversed along the horizontal midline to make contact and elicit a bounce sound off the opposite boundary. Our main analysis focused on the auditory-evoked event-related potential. For audio-visual (AV) trials, a sound accompanied the visual input when the ball contacted the opposite boundary (AV-synchronous), or the sound occurred before contact (AV-asynchronous). We also included audio-only and visual-only trials. AV-synchronous sounds elicited an earlier and attenuated auditory response relative to AV-asynchronous or audio-only events. In Experiment 2, we examined the roles of expectancy and multisensory integration in influencing this response. In addition to the audio-only, AV-synchronous, and AV-asynchronous conditions, participants were shown a ball that became occluded prior to reaching the boundary of the display, but elicited an expected sound at the point of occluded collision. The auditory response during the AV-occluded condition resembled that of the AV-synchronous condition, suggesting that expectations induced by a moving object can influence early auditory processing. Broadly, the results suggest that dynamic visual stimuli can help generate expectations about the timing of sounds, which then facilitates the processing of auditory information that matches these expectations.

Greater Visual Working Memory Capacity for Visually Matched Stimuli When They Are Perceived as Meaningful.

Almost all models of visual working memory-the cognitive system that holds visual information in an active state-assume it has a fixed capacity: Some models propose a limit of three to four objects, where others propose there is a fixed pool of resources for each basic visual feature. Recent findings, however, suggest that memory performance is improved for real-world objects. What supports these increases in capacity? Here, we test whether the meaningfulness of a stimulus alone influences working memory capacity while controlling for visual complexity and directly assessing the active component of working memory using EEG. Participants remembered ambiguous stimuli that could either be perceived as a face or as meaningless shapes. Participants had higher performance and increased neural delay activity when the memory display consisted of more meaningful stimuli. Critically, by asking participants whether they perceived the stimuli as a face or not, we also show that these increases in visual working memory capacity and recruitment of additional neural resources are because of the subjective perception of the stimulus and thus cannot be driven by physical properties of the stimulus. Broadly, this suggests that the capacity for active storage in visual working memory is not fixed but that more meaningful stimuli recruit additional working memory resources, allowing them to be better remembered.