Introducing ART: A new method for testing auditory memory with circular reproduction tasks.

Theories of visual working memory have seen significant progress through the use of continuous reproduction tasks. However, these tasks have mainly focused on studying visual features, with limited examples existing in the auditory domain. Therefore, it is unknown to what extent newly developed memory models reflect domain-general limitations or are specific to the visual domain. To address this gap, we developed a novel methodology: the Auditory Reproduction Task (ART). This task utilizes Shepard tones, which create an infinite rising or falling tone illusion by dissecting pitch chroma and height, to create a 1-360° auditory circular space. In Experiment 1, we validated the perceptual circularity and uniformity of this auditory stimulus space. In Experiment 2, we demonstrated that auditory working memory shows similar set size effects to visual working memory-report error increased at a set size of 2 relative to 1, caused by swap errors. In Experiment 3, we tested the validity of ART by correlating reproduction errors with commonly used auditory and visual working memory tasks. Analyses revealed that ART errors were significantly correlated with performance in both auditory and visual working memory tasks, albeit with a stronger correlation observed with auditory working memory. While these experiments have only scratched the surface of the theoretical and computational constraints on auditory working memory, they provide a valuable proof of concept for ART. Further research with ART has the potential to deepen our understanding of auditory working memory, as well as to explore the extent to which existing models are tapping into domain-general constraints.

Common Neural Mechanisms Control Attention and Working Memory.

Although previous studies point to qualitative similarities between working memory (WM) and attention, the degree to which these two constructs rely on shared neural mechanisms remains unknown. Focusing on one such potentially shared mechanism, we tested the hypothesis that selecting an item within WM utilizes similar neural mechanisms as selecting a visible item via a shift of attention. We used fMRI and machine learning to decode both the selection among items visually available and the selection among items stored in WM in human subjects (both sexes). Patterns of activity in visual, parietal, and to a lesser extent frontal cortex predicted the locations of the selected items. Critically, these patterns were strikingly interchangeable; classifiers trained on data during attentional selection predicted selection from WM, and classifiers trained on data during selection from memory predicted attentional selection. Using models of voxel receptive fields, we visualized topographic population activity that revealed gain enhancements at the locations of the externally and internally selected items. Our results suggest that selecting among perceived items and selecting among items in WM share a common mechanism. This common mechanism, analogous to a shift of spatial attention, controls the relative gains of neural populations that encode behaviorally relevant information.SIGNIFICANCE STATEMENT How we allocate our attention to external stimuli that we see and to internal representations of stimuli stored in memory might rely on a common mechanism. Supporting this hypothesis, we demonstrated that not only could patterns of human brain activity predict which items were selected during perception and memory, but that these patterns were interchangeable during external and internal selection. Additionally, this generalized selection mechanism operates by changes in the gains of the neural populations both encoding attended sensory representations and storing relevant memory representations.

Humans incorporate trial-to-trial working memory uncertainty into rewarded decisions.

Working memory (WM) plays an important role in action planning and decision making; however, both the informational content of memory and how that information is used in decisions remain poorly understood. To investigate this, we used a color WM task in which subjects viewed colored stimuli and reported both an estimate of a stimulus color and a measure of memory uncertainty, obtained through a rewarded decision. Reported memory uncertainty is correlated with memory error, showing that people incorporate their trial-to-trial memory quality into rewarded decisions. Moreover, memory uncertainty can be combined with other sources of information; after inducing expectations (prior beliefs) about stimuli probabilities, we found that estimates became shifted toward expected colors, with the shift increasing with reported uncertainty. The data are best fit by models in which people incorporate their trial-to-trial memory uncertainty with potential rewards and prior beliefs. Our results suggest that WM represents uncertainty information, and that this can be combined with prior beliefs. This highlights the potential complexity of WM representations and shows that rewarded decision can be a powerful tool for examining WM and informing and constraining theoretical, computational, and neurobiological models of memory.

Working memory is corrupted by strategic changes in search templates.

When searching for a specific object, we often form an image of the target, which we use as a search template. This template is thought to be maintained in working memory, primarily because of evidence that the contents of working memory influences search behavior. However, it is unknown whether this interaction applies in both directions. Here, we show that changes in search templates influence working memory. Participants were asked to remember the orientation of a line that changed every trial, and on some trials (75%) search for that orientation, but on remaining trials recall the orientation. Critically, we manipulated the target template by introducing a predictable context-distractors in the visual search task were always counterclockwise (or clockwise) from the search target. The predictable context produced a large bias in search. Importantly, we also found a similar bias in orientation memory reports, demonstrating that working memory and target templates were not held as completely separate, isolated representations. However, the memory bias was considerably smaller than the search bias, suggesting that, although there is a common source, the two may not be driven by a single, shared process.

Winter is coming: How humans forage in a temporally structured environment.

Much is known about visual search for single targets, but relatively little about how participants "forage" for multiple targets. One important question is how long participants will search before moving to a new display. Evidence suggests that participants should leave when intake drops below the average rate ("optimal foraging," Charnov, 1976). However, the real world has temporal structure (e.g., seasons) that could influence behavior. Does it matter if winter is coming and the next display will be worse than the last? We gave participants a series of search displays and asked them to collect targets as fast as possible. Target density was structured-rising and falling systematically across trials. We measured the duration for which participants foraged in each display (trials were terminated by participants). Foraging behavior was affected by temporal structure-counter to a simple optimal foraging account, observers searched displays longer when quality was falling compared to rising (Experiments 1 and 2). Additionally, we found that temporal structure altered explicit predictions about display quality (Experiment 2). These results demonstrate that foraging theories need to consider richer models of observers' representations of the world.

The attentional blink reveals the probabilistic nature of discrete conscious perception.

Attention and awareness are two tightly coupled processes that have been the subject of the same enduring debate: Are they allocated in a discrete or in a graded fashion? Using the attentional blink paradigm and mixture-modeling analysis, we show that awareness arises at central stages of information processing in an all-or-none manner. Manipulating the temporal delay between two targets affected subjects' likelihood of consciously perceiving the second target, but did not affect the precision of its representation. Furthermore, these results held across stimulus categories and paradigms, and they were dependent on attention having been allocated to the first target. The findings distinguish the fundamental contributions of attention and awareness at central stages of visual cognition: Conscious perception emerges in a quantal manner, with attention serving to modulate the probability that representations reach awareness.

Modeling visual working memory with the MemToolbox.

The MemToolbox is a collection of MATLAB functions for modeling visual working memory. In support of its goal to provide a full suite of data analysis tools, the toolbox includes implementations of popular models of visual working memory, real and simulated data sets, Bayesian and maximum likelihood estimation procedures for fitting models to data, visualizations of data and fit, validation routines, model comparison metrics, and experiment scripts. The MemToolbox is released under the permissive BSD license and is available at http://memtoolbox.org.

Meaningful objects avoid attribute amnesia due to incidental long-term memories.

Attribute amnesia describes the failure to unexpectedly report the attribute of an attended stimulus, likely reflecting a lack of working memory consolidation. Previous studies have shown that unique meaningful objects are immune to attribute amnesia. However, these studies used highly dissimilar foils to test memory, raising the possibility that good performance at the surprise test was based on an imprecise (gist-like) form of long-term memory. In Experiment 1, we explored whether a more sensitive memory test would reveal attribute amnesia in meaningful objects. We used a four-alternative-forced-choice test with foils having mis-matched exemplar (e.g., apple pie/pumpkin pie) and/or state (e.g., cut/full) information. Errors indicated intact exemplar, but not state information. Thus, meaningful objects are vulnerable to attribute amnesia under the right conditions. In Experiments 2A-2D, we manipulated the familiarity signals of test items by introducing a critical object as a pre-surprise target. In the surprise trial, this critical item matched one of the foil choices. Participants selected the critical object more often than other items. By demonstrating that familiarity influences responses in this paradigm, we suggest that meaningful objects are not immune to attribute amnesia but instead side-step the effects of attribute amnesia.

Probabilistic and rich individual working memories revealed by a betting game.

When asked to remember a color, do people remember a point estimate (e.g., a particular shade of red), a point estimate plus an uncertainty estimate, or are memory representations rich probabilistic distributions over feature space? We asked participants to report the color of a circle held in working memory. Rather than collecting a single report per trial, we had participants place multiple bets to create trialwise uncertainty distributions. Bet dispersion correlated with performance, indicating that internal uncertainty guided bet placement. While the first bet was on average the most precisely placed, the later bets systematically shifted the distribution closer to the target, resulting in asymmetrical distributions about the first bet. This resulted in memory performance improvements when averaging across bets, and overall suggests that memory representations contain more information than can be conveyed by a single response. The later bets contained target information even when the first response would generally be classified as a guess or report of an incorrect item, suggesting that such failures are not all-or-none. This paradigm provides multiple pieces of evidence that memory representations are rich and probabilistic. Crucially, standard discrete response paradigms underestimate the amount of information in memory representations.

Perception, performance, and detectability of conversational artificial intelligence across 32 university courses.

The emergence of large language models has led to the development of powerful tools such as ChatGPT that can produce text indistinguishable from human-generated work. With the increasing accessibility of such technology, students across the globe may utilize it to help with their school work-a possibility that has sparked ample discussion on the integrity of student evaluation processes in the age of artificial intelligence (AI). To date, it is unclear how such tools perform compared to students on university-level courses across various disciplines. Further, students' perspectives regarding the use of such tools in school work, and educators' perspectives on treating their use as plagiarism, remain unknown. Here, we compare the performance of the state-of-the-art tool, ChatGPT, against that of students on 32 university-level courses. We also assess the degree to which its use can be detected by two classifiers designed specifically for this purpose. Additionally, we conduct a global survey across five countries, as well as a more in-depth survey at the authors' institution, to discern students' and educators' perceptions of ChatGPT's use in school work. We find that ChatGPT's performance is comparable, if not superior, to that of students in a multitude of courses. Moreover, current AI-text classifiers cannot reliably detect ChatGPT's use in school work, due to both their propensity to classify human-written answers as AI-generated, as well as the relative ease with which AI-generated text can be edited to evade detection. Finally, there seems to be an emerging consensus among students to use the tool, and among educators to treat its use as plagiarism. Our findings offer insights that could guide policy discussions addressing the integration of artificial intelligence into educational frameworks.

How selection in the mind is different from attention to the world.

Attentional mechanisms allow us to focus on objects that would help us achieve our goals while ignoring those that would distract us. Attention can also be focused internally toward specific items in memory. But does selection within memory work similarly to selection within perception? Perceptual attention is fast and effective at selecting regions of space. Across five experiments, we used a memory search task to investigate whether spatial selection is also efficient for selection in memory. Participants remembered four items on a grid before being asked to access their memory of one item and update one of its features. We found that it took longer to access an item when referenced by its spatial location than by its color, despite memory accuracy for location being superior. We conclude that there must be multiple, distinct memory representations in the brain and that selection in memory is different from perceptual selection. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

How do expectations change behavior? Investigating the contributions at encoding versus decision-making.

Expectations about the environment play a large role in shaping behavior, but how does this occur? Do expectations change the way we perceive the world, or just our decisions based on unbiased perceptions? We investigated the relative contributions of priors to these 2 stages by manipulating when information about expected color was provided. We compared cases where the prior could affect encoding into perceptual/working memory representations (e.g., when provided prestimulus) against cases where it could not (e.g., when given at response after a delay). Although priors had a minor influence on encoding, the bulk of the effects were at decision-making. Furthermore, these effects appeared to be distinct. The effect on decision-making was Bayesian-like, with priors inducing bias while improving precision. In contrast, the same priors at encoding improved precision without causing changes in bias. Priors do not just affect encoding or decision-making, but appear to affect both, via distinct mechanisms. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

No evidence that the retro-cue benefit requires reallocation of memory resources.

Selective mechanisms allow us to prioritize items held in working memory. Does this reflect reallocation of working memory resources? We examined a critical prediction of this account-that reallocating more resources from one item to another should provide a greater benefit. We used a reward manipulation to create variable allocation of resources. Subsequently, a retro-cue instructed participants to drop a memory item. This retro-cue improved performance for the prioritized items relative to a neutral baseline. However, in contrast to the prevailing reallocation account, we found no difference between dropping a higher versus lower reward item. Importantly, removal of high versus low reward items led to better encoding of subsequently presented items, demonstrating that our reward manipulation was successful. While allocation of resources can influence the encoding and storage of new information into working memory, reallocation does not appear to be essential for selection effects in working memory.

Perception is rich and probabilistic.

When we see a stimulus, e.g. a star-shaped object, our intuition is that we should perceive a single, coherent percept (even if it is inaccurate). But the neural processes that support perception are complex and probabilistic. Simple lines cause orientation-selective neurons across a population to fire in a probabilistic-like manner. Does probabilistic neural firing lead to non-probabilistic perception, or are the representations behind perception richer and more complex than intuition would suggest? To test this, we briefly presented a complex shape and had participants report the correct shape from a set of options. Rather than reporting a single value, we used a paradigm designed to encourage to directly report a representation over shape space-participants placed a series of Gaussian bets. We found that participants could report more than point-estimates of shape. The spread of responses was correlated with accuracy, suggesting that participants can convey a notion of relative imprecision. Critically, as participants placed more bets, the mean of responses show increased precision. The later bets were systematically biased towards the target rather than haphazardly placed around bet 1. These findings strongly indicate that participants were aware of more than just a point-estimate; Perceptual representations are rich and likely probabilistic.

Training modulates memory-driven capture.

Attention is captured by information matching the contents of working memory. Though many factors modulate the amount of capture, there is surprising resistance to cognitive control. Capture occurs even when participants are instructed either that an item would never be a target or to drop that item from memory. Does the persistence of capture under these conditions reflect a rigidity in capture, or can properly motivated participants learn to completely suppress distractors and/or completely drop items from memory? Surprisingly, no studies have looked at the influence of extensive training of involuntary capture from working memory items. Here, we addressed whether training leads to a reduction or even elimination of memory-driven capture. After memorizing a single object, participants were cued to remember or to forget this object. Subsequently, they were asked to execute a search task. To measure capture, we compared search performances in displays that did and did not contain a distractor matching the earlier memorized object. Participants completed multiple experimental sessions over four days. The results showed that attentional capture by to-be-remembered distractors was reduced, but not eliminated in subsequent sessions compared with the first session. Training did not impact capture by to-be-forgotten objects. The results suggest observable, but limited, cognitive control over memory-driven capture.

Object features fail independently in visual working memory: evidence for a probabilistic feature-store model.

The world is composed of features and objects and this structure may influence what is stored in working memory. It is widely believed that the content of memory is object-based: Memory stores integrated objects, not independent features. We asked participants to report the color and orientation of an object and found that memory errors were largely independent: Even when one of the object's features was entirely forgotten, the other feature was often reported. This finding contradicts object-based models and challenges fundamental assumptions about the organization of information in working memory. We propose an alternative framework involving independent self-sustaining representations that may fail probabilistically and independently for each feature. This account predicts that the degree of independence in feature storage is determined by the degree of overlap in neural coding during perception. Consistent with this prediction, we found that errors for jointly encoded dimensions were less independent than errors for independently encoded dimensions.

The road to long-term memory: Top-down attention is more effective than bottom-up attention for forming long-term memories.

Does the strength of representations in long-term memory (LTM) depend on which type of attention is engaged? We tested participants' memory for objects seen during visual search. We compared implicit memory for two types of objects-related-context nontargets that grabbed attention because they matched the target defining feature (i.e., color; top-down attention) and salient distractors that captured attention only because they were perceptually distracting (bottom-up attention). In Experiment 1, the salient distractor flickered, while in Experiment 2, the luminance of the salient distractor was alternated. Critically, salient and related-context nontargets produced equivalent attentional capture, yet related-context nontargets were remembered far better than salient distractors (and salient distractors were not remembered better than unrelated distractors). These results suggest that LTM depends not only on the amount of attention but also on the type of attention. Specifically, top-down attention is more effective in promoting the formation of memory traces than bottom-up attention.

Object-based selection in visual working memory.

Attentional mechanisms in perception can operate over locations, features, or objects. However, people direct attention not only towards information in the external world, but also to information maintained in working memory. To what extent do perception and memory draw on similar selection properties? Here we examined whether principles of object-based attention can also hold true in visual working memory. Experiment 1 examined whether object structure guides selection independently of spatial distance. In a memory updating task, participants encoded two rectangular bars with colored ends before updating two colors during maintenance. Memory updates were faster for two equidistant colors on the same object than on different objects. Experiment 2 examined whether selection of a single object feature spreads to other features within the same object. Participants memorized two sequentially presented Gabors, and a retro-cue indicated which object and feature dimension (color or orientation) would be most relevant to the memory test. We found stronger effects of object selection than feature selection: accuracy was higher for the uncued feature in the same object than the cued feature in the other object. Together these findings demonstrate effects of object-based attention on visual working memory, at least when object-based representations are encouraged, and suggest shared attentional mechanisms across perception and memory.

Selection in working memory is resource-demanding: Concurrent task effects on the retro-cue effect.

In a retro-cue paradigm, after memorizing a set of objects, people are cued to remember only a subset. Improved memory from the retro-cue suggests that selection processes can benefit items stored in working memory. Does selection in working memory require attention? If so, an attention-demanding task should disrupt retro-cue effects. Studies using a dual-task paradigm have found mixed results, with only one study (Janczyk & Berryhill, Attention, Perception, and Psychophysics, 76 (3), 715-724, 2014) showing a decreased retro-cue effect by a secondary task. Here we explore a potential issue in that study - the temporal overlap of the secondary task response with the memory test presentation. This raises questions about whether the secondary task was impairing selection processes in memory or was impacting the memory response. We replicated their paradigm by inserting a tone discrimination task at the retro-cue offset, but we also included a condition in which the tone task and the memory test were temporally separated. In Experiment 1, performing the tone task did not impair the retro-cue effect. In Experiment 2, we added an articulatory suppression task as in Janczyk and Berryhill's study, and we found that the requirement to execute the tone task impaired retro-cue effects. This impairment was independent of whether the tone and memory tasks overlapped. These findings suggest that internal prioritization can be impaired by dual-task interference, but may only occur when such interference is robust enough, for example, due to switching between multiple tasks.

What are the units of storage in visual working memory?

An influential theory suggests that integrated objects, rather than individual features, are the fundamental units that limit our capacity to temporarily store visual information (S. J. Luck & E. K. Vogel, 1997). Using a paradigm that independently estimates the number and precision of items stored in working memory (W. Zhang & S. J. Luck, 2008), here we show that the storage of features is not cost-free. The precision and number of objects held in working memory was estimated when observers had to remember either the color, the orientation, or both the color and orientation of simple objects. We found that while the quantity of stored objects was largely unaffected by increasing the number of features, the precision of these representations dramatically decreased. Moreover, this selective deterioration in object precision depended on the multiple features being contained within the same objects. Such fidelity costs were even observed with change detection paradigms when those paradigms placed demands on the precision of the stored visual representations. Taken together, these findings not only demonstrate that the maintenance of integrated features is costly; they also suggest that objects and features affect visual working memory capacity differently.