Flexible attention allocation to visual and auditory working memory tasks: manipulating reward induces a trade-off

Evidence for the Beneficial Effect of Reward on Working Memory: A Meta-Analytic Study

Rewards act as external motivators and can improve performance in various cognitive tasks. However, previous research demonstrated mixed findings regarding the effect of reward on working memory (WM) performance, and the question of whether reward enhances WM performance is arguable. It remains unclear how the effect of reward on WM can be influenced by various factors, such as types of reward and experimental paradigms. In this meta-analytic study, we systematically investigated the effect of reward on WM by analyzing data from 51 eligible studies involving a total of 1767 participants. Our results showed that reward robustly enhanced WM performance, with non-monetary rewards inducing more benefits than monetary rewards. This may be because, while both types of reward could induce extrinsic motivation, non-monetary rewards enhanced intrinsic motivation while monetary rewards reduced it. Notably, all three reward methods-reward binding, reward expectation, and subliminal reward-effectively improved WM performance, with the reward binding paradigm exhibiting the greatest effects. This finding suggests that the reward effect can be attributed to both increasing the total amount of WM resources and improving the flexibility of resource reallocation. Moreover, the type of WM, the experimental paradigms, and the outcome measures are three moderators that should be jointly considered when assessing the reward effects on WM. Overall, this meta-analytic study provides solid evidence that reward improves WM performance and reveals possible mechanisms underlying these improvements.

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.

The Relation Between Attention and Memory

The relation between attention and memory has long been deemed important for understanding cognition, and it was heavily researched even in the first experimental psychology laboratory by Wilhelm Wundt and his colleagues. Since then, the importance of the relation between attention and memory has been explored in myriad subdisciplines of psychology, and we incorporate a wide range of these diverse fields. Here, we examine some of the practical consequences of this relation and summarize work with various methodologies relating attention to memory in the fields of working memory, long-term memory, individual differences, life-span development, typical brain function, and neuropsychological conditions. We point out strengths and unanswered questions for our own embedded processes view of information processing, which is used to organize a large body of evidence. Last, we briefly consider the relation of the evidence to a range of other theoretical views before drawing conclusions about the state of the field.

Stress, working memory, and academic performance: a neuroscience perspective

The relationship between stress and working memory (WM) is crucial in determining students' academic performance, but the interaction between these factors is not yet fully understood. WM is a key cognitive function that is important for learning academic skills, such as reading, comprehension, problem-solving, and math. Stress may negatively affect cognition, including WM, via various mechanisms; these include the deleterious effect of glucocorticoids and catecholamines on the structure and function of brain regions that are key for WM, such as the prefrontal cortex and hippocampus. This review explores the mechanisms underlying how stress impacts WM and how it can decrease academic performance. It highlights the importance of implementing effective stress-management strategies to protect WM function and improve academic performance.

Dopamine receptor activation regulates reward expectancy signals during cognitive control in primate prefrontal neurons

Dopamine neurons respond to reward-predicting cues but also modulate information processing in the prefrontal cortex essential for cognitive control. Whether dopamine controls reward expectation signals in prefrontal cortex that motivate cognitive control is unknown. We trained two male macaques on a working memory task while varying the reward size earned for successful task completion. We recorded neurons in lateral prefrontal cortex while simultaneously stimulating dopamine D1 receptor (D1R) or D2 receptor (D2R) families using micro-iontophoresis. We show that many neurons predict reward size throughout the trial. D1R stimulation showed mixed effects following reward cues but decreased reward expectancy coding during the memory delay. By contrast, D2R stimulation increased reward expectancy coding in multiple task periods, including cueing and memory periods. Stimulation of either dopamine receptors increased the neurons' selective responses to reward size upon reward delivery. The differential modulation of reward expectancy by dopamine receptors suggests that dopamine regulates reward expectancy necessary for successful cognitive control.

Constraints of attention, stimulus modality, and feature similarity in working memory

Two of the most important concepts in working memory that differentiate many theories are the role of attention and similarity between items. Investigators have debated whether there is a central, general resource of attention, and whether interference between items depends mostly on their modality and type of code (i.e., verbal/acoustic versus visual/spatial coding) or upon multiple dimensions of feature similarity even within a modality. Here, we examine results from three experiments in which the features of items to be remembered differed for visual objects in color or orientation, or for acoustic objects in noise duration or tone pitch. There were one or two of these sets on a trial and, when there were two sets, the similarity between their features varied: there were sets in different modalities, sets with different feature types within a modality, or sets of the same feature type. One-set trials consistently produced superior performance. For two-set trials, dissimilarity of the sets mattered only when both sets had to be attended, compared with attention to only one set. Feature differences within a modality mattered at least as much as between-modality differences. The findings conflict with what would be expected if modality were the sole organizing principle and support a working memory model in which a capacity-limited attention is constrained by the feature similarity of task-relevant items.

Attention allocation between item and order information in short-term memory

In immediate memory for verbal lists, recently it has been shown that participants can choose to carry out encoding that prioritises readiness for an item test at some cost to order information or, conversely, that prioritises readiness for an order test at a cost to item information. Here, we ask whether participants can control attention to items and order in a graded fashion. We examined this issue by manipulating the percentage of order or item test trials participants would receive in a block (for each type of test, 25%, 50%, 75%, or 100% of the trials in a block). Overall, the results revealed that participants were able to allocate their attention in a fine-grained manner that took into account the trial distribution within the block. However, there was a difference between the effects of allocating attention to item versus order. Divided attention, compared with full attention to one attribute, had an asymmetry, such that divided attention impaired order performance more than item performance. The exact point at which this asymmetry could be seen differed between two experiments, which included different item tests (fragment completion vs. free recall). The results suggest a common resource for item and order encoding and/or retention in working memory, which can be voluntarily allocated to different mixtures of these two attributes.

Editing reality in the brain

Recent information technologies such as virtual reality (VR) and augmented reality (AR) allow the creation of simulated sensory worlds with which we can interact. Using programming language, digital details can be overlaid onto displays of our environment, confounding what is real and what has been artificially engineered. Natural language, particularly the use of direct verbal suggestion (DVS) in everyday and hypnotic contexts, can also manipulate the meaning and significance of objects and events in ourselves and others. In this review, we focus on how socially rewarding language can construct and influence reality. Language is symbolic, automatic and flexible and can be used to augment bodily sensations e.g. feelings of heaviness in a limb or suggest a colour that is not there. We introduce the term 'suggested reality' (SR) to refer to the important role that language, specifically DVS, plays in constructing, maintaining and manipulating our shared reality. We also propose the term edited reality to encompass the wider influence of information technology and linguistic techniques that results in altered subjective experience and review its use in clinical settings, while acknowledging its limitations. We develop a cognitive model indicating how the brain's central executive structures use our personal and linguistic-based narrative in subjective awareness, arguing for a central role for language in DVS. A better understanding of the characteristics of VR, AR and SR and their applications in everyday life, research and clinical settings can help us to better understand our own reality and how it can be edited.

Reward and loss incentives improve spatial working memory by shaping trial-by-trial posterior frontoparietal signals

Integrating motivational signals with cognition is critical for goal-directed activities. The mechanisms that link neural changes with motivated working memory continue to be understood. Here, we tested how externally cued and non-cued (internally represented) reward and loss impact spatial working memory precision and neural circuits in human subjects using fMRI. We translated the classic delayed-response spatial working memory paradigm from non-human primate studies to take advantage of a continuous numeric measure of working memory precision, and the wealth of translational neuroscience yielded by these studies. Our results demonstrated that both cued and non-cued reward and loss improved spatial working memory precision. Visual association regions of the posterior prefrontal and parietal cortices, specifically the precentral sulcus (PCS) and intraparietal sulcus (IPS), had increased BOLD signal during incentivized spatial working memory. A subset of these regions had trial-by-trial increases in BOLD signal that were associated with better working memory precision, suggesting that these regions may be critical for linking neural signals with motivated working memory. In contrast, regions straddling executive networks, including areas in the dorsolateral prefrontal cortex, anterior parietal cortex and cerebellum displayed decreased BOLD signal during incentivized working memory. While reward and loss similarly impacted working memory processes, they dissociated during feedback when money won or avoided in loss was given based on working memory performance. During feedback, the trial-by-trial amount and valence of reward/loss received was dissociated amongst regions such as the ventral striatum, habenula and periaqueductal gray. Overall, this work suggests motivated spatial working memory is supported by complex sensory processes, and that the IPS and PCS in the posterior frontoparietal cortices may be key regions for integrating motivational signals with spatial working memory precision.

Motivation improves working memory by two processes: Prioritisation and retrieval thresholds

Motivation can improve performance when the potential rewards outweigh the cost of effort expended. In working memory (WM), people can prioritise rewarded items at the expense of unrewarded items, suggesting a fixed memory capacity. But can capacity itself change with motivation? Across four experiments (N = 30-34) we demonstrate motivational improvements in WM even when all items were rewarded. However, this was not due to better memory precision, but rather better selection of the probed item within memory. Motivational improvements operated independently of encoding, maintenance, or attention shifts between items in memory. Moreover, motivation slowed responses. This contrasted with the benefits of rewarding items unequally, which allowed prioritisation of one item over another. We conclude that motivation can improve memory recall, not via precision or capacity, but via speed-accuracy trade-offs when selecting the item to retrieve.

Determining Whether Tai Chi Chuan Is Related to the Updating Function in Older Adults: Differences Between Practitioners and Controls

Background

Tai Chi Chuan (TCC) is an effective method for delaying cognitive decline in older adults. However, in older adults, the association between long-term TCC practice and working memory updating has not been extensively studied.

Objective

This cross-sectional study investigated how updating function operationalized via Reaction Times (RTs) and Accuracy Rates (ARs) of N-Back tasks being measured in a laboratory setting is related to long term practice of TCC.

Methods

Twenty-six healthy elderly people participated in this experiment. According to the duration of time TCC was practiced, 13 subjects in the TCC group had more than 5 years of experience with TCC exercise, and 13 elderly subjects who had not been systematically exposed to mind-body exercise were assigned to the control group. The N-back task was administered to every participant to evaluate the updating function.

Results

The TCC group had faster RTs than the control group (p < 0.05). For the 1-back task, the TCC group showed faster RTs than the control group; for the 2-back task, the TCC group exhibited faster RTs than the control group. The TCC group had higher ARs than the control group (p < 0.05). For the 1-back task, the TCC group showed higher ARs than the control group; for the 2-back task, the TCC group exhibited higher ARs than the control group.

Conclusions

Long-term TCC practitioners exhibit a better updating function as compared to controls who did not practice TCC. Thus, our findings suggest that long-term TCC positively influences the updating function of older adults, making it, in turn, an effective mind-body exercise to maintain specific aspects of cognitive functioning.

The effect of apparent distance on peripheral target detection

Previous research suggests that peripheral target detection is modulated by viewing distance and distance simulated by pictorial cues and optic flow. In the latter case, it is unclear what cues contribute to the effect of distance. The current study evaluated the effect of distance on peripheral detection in a virtual three-dimensional environment. Experiments 1–3 used a continuous, dynamic central task that simulated observers traveling either actively or passively through a virtual environment following a car. Peripheral targets were flashed on checkerboard-covered walls to the left and right of the path of motion, at a near and a far distance from the observer. The retinal characteristics of the targets were identical across distances. Experiment 1 found more accurate and faster detection for near targets compared to far targets, especially for larger eccentricities. Experiment 2 equated the predictability of target onset across distances and found the near advantage for larger eccentricities in accuracy but a much smaller effect in reaction time (RT). Experiment 3 removed the checkerboard background implemented in Experiments 1 and 2, and Experiment 4 manipulated several static, monocular cues. Experiments 3 and 4 found that the variation in the density of the checkerboard backgrounds could explain the main effect of distance on accuracy but could not completely account for the interaction between target distance and eccentricity. These results suggest that attention is modulated by target distance, but the effect is small. Finally, there were consistent divided attention costs in the central car-following task but not the peripheral detection task.

The Influence of Cognitive Load on Distractor-Response Bindings

Binding theories postulate an integration of stimulus and response features into temporary episodic traces or event files. In general, in the visual binding literature, attention is considered to be necessary to feature binding, and a higher cognitive load can lead to worse performance. On the other hand, in stimulus-response binding theories, central attention is not regarded as necessary in binding effects. A possible discrepancy between the visual feature binding findings and the findings in stimulus-response binding studies could lie in the amount of central load implemented, whereas another discrepancy was related to a specific type of process that was manipulated. In the present study, load was manipulated in three levels, such as no load, low load, and high load, and the binding effects were tested under each condition. Load was manipulated by using a secondary task, which was to be carried out simultaneously with the primary task. Additionally, the influence of targeting different working memory processes (maintenance and updating) was examined by varying the time point of the presentation of the secondary task. The results indicate that, under high load, binding effects are observed if memory contents are merely maintained, but not observed when memory contents are actively updated.

What affects the magnitude of age-related dual-task costs in working memory? The role of stimulus domain and access to semantic representations

Although there is evidence that the effect of including a concurrent processing demand on the storage of information in working memory is disproportionately larger for older than younger adults, not all studies show this age-related impairment, and the critical factors responsible for any such impairment remain elusive. Here we assess whether domain overlap between storage and processing activities, and access to semantic representations, are important determinants of performance in a sample of younger and older adults (N = 119). We developed four versions of a processing task by manipulating the type of stimuli involved (either verbal or non-verbal) and the decision that participants had to make about the stimuli presented on the screen. Participants either had to perform a spatial judgement, in deciding whether the verbal or non-verbal item was presented above or below the centre of the screen, or a semantic judgement, in deciding whether the stimulus refers to something living or not living. The memory task was serial-ordered recall of visually presented letters. The study revealed a large increase in age-related memory differences when concurrent processing was required. These differences were smaller when storage and processing activities both used verbal materials. Dual-task effects on processing were also disproportionate for older adults. Age differences in processing performance appeared larger for tasks requiring spatial decisions rather than semantic decisions. We discuss these findings in relation to three competing frameworks of working memory and the extant literature on cognitive ageing.

Attention effects in working memory that are asymmetric across sensory modalities

A key unanswered question about working memory is the nature of interference between items. At one extreme of existing theories, interference occurs between any two items because of a general capacity limit. At another extreme, interference depends on the similarity between particular features of different items. We examine this question in three experiments by presenting two sets of items on each trial, comprising tones or colors, with three levels of similarity between the two sets: cross-modal, unimodal with different marking features (two different musical instruments or shapes), and unimodal with the same marking feature. Another question is the extent to which the entry of presented items into working memory is obligatory or optional, which we examined by requiring retention of the first, the second, or both sets of stimuli for a recognition test shortly after the presentation of the two sets. The combination of the set similarity and attention manipulations allows us to draw conclusions about the nature of working-memory storage. The findings were not entirely in accord with any pre-existing theory. The effects of feature similarity were present in both modalities but more pronounced for sounds, whereas the detrimental effects of attention to both sets for retention occurred only for visual stimuli. Based on the findings we suggest a new, hybrid conception of working memory storage.

Monetary incentives have only limited effects on auditory distraction: evidence for the automaticity of cross-modal attention capture

The duplex-mechanism account of auditory distraction postulates that two distinct forms of auditory distraction can be distinguished by whether or not they can be cognitively controlled. While the interference-by-process component of auditory distraction is postulated to be automatic and independent of cognitive control, the stimulus-aspecific attention capture by auditory deviants and the stimulus-specific attentional diversion by auditorily presented distractor sentences should be suppressed by increased task engagement. Here we test whether incentive-induced changes in task engagement affect the disruption of serial recall by auditory deviants (Experiment 1) and distractor sentences (Experiment 2). Monetary incentives substantially affected recall performance in both experiments. However, the incentive-induced changes in task engagement had only limited effects on auditory distraction. In Experiment 2, increased task engagement was associated with a small decrease of distraction relative to a quiet condition, but strong effects of auditory distraction on performance persisted in conditions of high task engagement in both experiments. Most importantly, and in contrast to the predictions of the duplex-mechanism account, the effects of stimulus-aspecific attention capture (Experiment 1) and stimulus-specific attentional diversion (Experiment 2) remained unaffected by incentive-induced changes in task engagement. These findings are consistent with an automatic-capture account according to which only the processes responsible for the deliberate memorization of the target items are dependent on controlled mental effort while the attention capture by auditory deviants and the attentional diversion by distractor speech are largely automatic.

Allocation of Driver Attention for Varying In-Vehicle System Modalities

OBJECTIVE

This paper examines drivers' allocation of attention using response time to a tactile detection response task (TDRT) while interacting with an in-vehicle information system (IVIS) over time.

BACKGROUND

Longer TDRT response time is associated with higher cognitive workload. However, it is not clear what role is assumed by the human and system in response to varying in-vehicle environments over time.

METHOD

A driving simulator study with 24 participants was conducted with a restaurant selection task of two difficulty levels (easy and hard) presented in three modalities (audio only, visual only, hybrid). A linear mixed-effects model was applied to identify factors that affect TDRT response time. A nonparametric time-series model was also used to explore the visual attention allocation under the hybrid mode over time.

RESULTS

The visual-only mode significantly increased participants' response time compared with the audio-only mode. Females took longer to respond to the TDRT when engaged with an IVIS. The study showed that participants tend to use the visual component more toward the end of the easy tasks, whereas the visual mode was used more at the beginning of the harder tasks.

CONCLUSION

The visual-only mode of the IVIS increased drivers' cognitive workload when compared with the auditory-only mode. Drivers showed different visual attention allocation during the easy and hard restaurant selection tasks in the hybrid mode.

APPLICATION

The findings can help guide the design of automotive user interfaces and help manage cognitive workload.

Prioritization within visual working memory reflects a flexible focus of attention

When motivated, people can keep nonrecent items in a list active during the presentation of new items, facilitating fast and accurate recall of the earlier items. It has been proposed that this occurs by flexibly orienting attention to a single prioritized list item, thus increasing the amount of attention-based maintenance directed toward this item at the expense of other items. This is manipulated experimentally by associating a single distinct feature with a higher reward value, such as a single red item in a list of black items. These findings may be more parsimoniously explained under a distinctiveness of encoding framework rather than a flexible attention allocation framework. The retrieval advantage for the prioritized list position may be because the incongruent feature stands out in the list perceptually and causes it to become better encoded. Across three visual working memory experiments, we contrast a flexible attention theory against a distinctiveness of encoding theory by manipulating the reward value associated with the incongruent feature. Findings from all three experiments show strong support in favor of the flexible attention theory and no support for the distinctiveness of encoding theory. We also evaluate and find no evidence that strategy use, motivation, or tiredness/fatigue associated with reward value can adequately explain flexible prioritization of attention. Flexible attentional prioritization effects may be best understood under the context of an online attentional refreshing mechanism.

Cognitive aging and verbal labeling in continuous visual memory

The decline of working memory (WM) is a common feature of general cognitive decline, and visual and verbal WM capacity appear to decline at different rates with age. Visual material may be remembered via verbal codes or visual traces, or both. Souza and Skóra, Cognition, 166, 277-297 (2017) found that labeling boosted memory in younger adults by activating categorical visual long-term memory (LTM) knowledge. Here, we replicated this and tested whether it held in healthy older adults. We compared performance in silence, under instructed overt labeling (participants were asked to say color names out loud), and articulatory suppression (repeating irrelevant syllables to prevent labeling) in the delayed estimation paradigm. Overt labeling improved memory performance in both age groups. However, comparing the effect of overt labeling and suppression on the number of coarse, categorical representations in the two age groups suggested that older adults used verbal labels subvocally more than younger adults, when performing the task in silence. Older adults also appeared to benefit from labels differently than younger adults. In younger adults labeling appeared to improve visual, continuous memory, suggesting that labels activated visual LTM representations. However, for older adults, labels did not appear to enhance visual, continuous representations, but instead boosted memory via additional verbal (categorical) memory traces. These results challenged the assumption that visual memory paradigms measure the same cognitive ability in younger and older adults, and highlighted the importance of controlling differences in age-related strategic preferences in visual memory tasks.

Attentional flexibility and prioritization improves long-term memory

Recent evidence suggests the focus of attention (FoA) is a flexible resource within working memory (WM) used to temporarily maintain some information in a highly accessible state. This flexibility comes at the expense of other representations, demonstrating a resource trade-off in WM maintenance. The present experiments evaluate how flexibility within the FoA impacts long-term memory (LTM) for semantically meaningful information. A WM probe-recognition task was used in which two items were presented in black and a single item was presented in red. To encourage the prioritization and uninterrupted preferential maintenance of specific items, a process we call online refreshing, the red item was associated with a greater point-reward value than were the black items. This WM task was followed by a surprise delayed LTM test. In Experiment 1, the FoA flexibly adjusted to maintain non-recent semantic information with evidence for a resource trade-off across list positions. Flexibility also directly improved LTM. In Experiment 2, reward value was equated across red and black items to evaluate whether an alternative explanation, distinctiveness of encoding, could account for the LTM findings. When reward value was equated, the cued item did not encourage flexible orienting of the FoA toward non-recent items and there was no benefit of the distinct red item on LTM performance. While supportive of past research, these data further demonstrate that semantic information can be flexibly prioritized at the expense of other list positions and that this is directly tied to improvements in LTM.

Reward

Neurons throughout frontal cortex show robust responses to rewards, but a challenge is determining the specific function served by these different reward signals. Most neuropsychiatric disorders involve dysfunction of circuits between frontal cortex and subcortical structures, such as the striatum. There are multiple frontostriatal loops, and different neuropsychiatric disorders involve different loops to greater or lesser extents. Understanding the role of reward in each of these different circuits is a necessary step in developing novel treatments for these disorders. This chapter summarizes the recent literature that has identified the role of reward in different subregions of the frontal cortex. Orbitofrontal cortex integrates information about multiple aspects of expected rewards in order to derive their value, which can then be used to decide between alternative potential rewards. Neurons in anterior cingulate cortex encode the difference between the expected reward and the actual outcome. This information is useful for learning, since it can ensure that behavior changes when the outcome was not anticipated. Reward also affects signals in lateral prefrontal cortex related to attention and response selection, ensuring that behaviors are optimally prioritized. Finally, the chapter discusses how reward signals contribute to social processing and autonomic control.

Neural mechanisms of attending to items in working memory

Working memory, the ability to keep recently accessed information available for immediate manipulation, has been proposed to rely on two mechanisms that appear difficult to reconcile: self-sustained neural firing, or the opposite-activity-silent synaptic traces. Here we review and contrast models of these two mechanisms, and then show that both phenomena can co-exist within a unified system in which neurons hold information in both activity and synapses. Rapid plasticity in flexibly-coding neurons allows features to be bound together into objects, with an important emergent property being the focus of attention. One memory item is held by persistent activity in an attended or "focused" state, and is thus remembered better than other items. Other, previously attended items can remain in memory but in the background, encoded in activity-silent synaptic traces. This dual functional architecture provides a unified common mechanism accounting for a diversity of perplexing attention and memory effects that have been hitherto difficult to explain in a single theoretical framework.

Relative reinforcer rates determine pigeons' attention allocation when separately trained stimuli are presented together

Previous research suggests that organisms allocate more attention to stimuli associated with higher reinforcer rates. This finding has been replicated several times when stimuli are trained together as compounds, but not in other procedures. Thus, the generality of the relation between relative reinforcer rates and divided attention is not well established. Therefore, we investigated whether relative reinforcer rates determine attention allocation when stimuli are trained separately and then encountered together. Pigeons learned to associate two colors and two frequencies of key light on/off alternation with a left or right comparison key in a symbolic 0-s delayed matching-to-sample task. Across conditions, we varied the probability of reinforcement associated with each stimulus dimension during training. After training, we introduced test trials in which a color and flash-frequency stimulus were presented simultaneously. During sample-stimulus presentation in test trials, all pigeons preferred the stimulus associated with the higher reinforcer rate, suggesting that more attention was allocated to that stimulus. Interestingly, such attention allocation did not result in preference for the comparison that matched that stimulus. Instead, all pigeons preferred the comparison that was physically closer to the stimulus associated with the higher reinforcer rate, suggesting that comparison choice was controlled by the location of that stimulus. Nevertheless, overall, our results provide the first evidence that relative reinforcer rates determine divided attention between separately trained stimuli and thus demonstrate the generality of the relation between relative reinforcement and attention allocation. We suggest several avenues for future research to establish further the generality of this relation.

Extrinsic Cognitive Load Impairs Spoken Word Recognition in High- and Low-Predictability Sentences

OBJECTIVES

Listening effort (LE) induced by speech degradation reduces performance on concurrent cognitive tasks. However, a converse effect of extrinsic cognitive load on recognition of spoken words in sentences has not been shown. The aims of the present study were to (a) examine the impact of extrinsic cognitive load on spoken word recognition in a sentence recognition task and (b) determine whether cognitive load and/or LE needed to understand spectrally degraded speech would differentially affect word recognition in high- and low-predictability sentences. Downstream effects of speech degradation and sentence predictability on the cognitive load task were also examined.

DESIGN

One hundred twenty young adults identified sentence-final spoken words in high- and low-predictability Speech Perception in Noise sentences. Cognitive load consisted of a preload of short (low-load) or long (high-load) sequences of digits, presented visually before each spoken sentence and reported either before or after identification of the sentence-final word. LE was varied by spectrally degrading sentences with four-, six-, or eight-channel noise vocoding. Level of spectral degradation and order of report (digits first or words first) were between-participants variables. Effects of cognitive load, sentence predictability, and speech degradation on accuracy of sentence-final word identification as well as recall of preload digit sequences were examined.

RESULTS

In addition to anticipated main effects of sentence predictability and spectral degradation on word recognition, we found an effect of cognitive load, such that words were identified more accurately under low load than high load. However, load differentially affected word identification in high- and low-predictability sentences depending on the level of sentence degradation. Under severe spectral degradation (four-channel vocoding), the effect of cognitive load on word identification was present for high-predictability sentences but not for low-predictability sentences. Under mild spectral degradation (eight-channel vocoding), the effect of load was present for low-predictability sentences but not for high-predictability sentences. There were also reliable downstream effects of speech degradation and sentence predictability on recall of the preload digit sequences. Long digit sequences were more easily recalled following spoken sentences that were less spectrally degraded. When digits were reported after identification of sentence-final words, short digit sequences were recalled more accurately when the spoken sentences were predictable.

CONCLUSIONS

Extrinsic cognitive load can impair recognition of spectrally degraded spoken words in a sentence recognition task. Cognitive load affected word identification in both high- and low-predictability sentences, suggesting that load may impact both context use and lower-level perceptual processes. Consistent with prior work, LE also had downstream effects on memory for visual digit sequences. Results support the proposal that extrinsic cognitive load and LE induced by signal degradation both draw on a central, limited pool of cognitive resources that is used to recognize spoken words in sentences under adverse listening conditions.

Storage and processing in working memory: Assessing dual-task performance and task prioritization across the adult lifespan

There is a theoretical disagreement in the working memory literature, with some proposing that the storage and processing of information rely on distinct parts of the cognitive system and others who posit that they rely, to some extent, on a shared attentional capacity. This debate is mirrored in the literature on working memory and aging, where there have been mixed findings on the ability of older adults to perform simultaneous storage and processing tasks. We assess the overlap between storage and processing and how this changes with age using a procedure in which both tasks have been carefully adjusted to produce comparable levels of single-task performance across a sample (N = 164) of participants aged 18-81. By manipulating incentives to perform one task over the other, this procedure was also capable of disentangling concurrence costs (single- vs. dual-task performance) from prioritization costs (relative payoffs for storage vs. processing performance) in a theoretically meaningful manner. The study revealed a large general cost to serial letter recall performance associated with concurrent performance of an arithmetic verification processing task, a concurrence cost that increased with age. For the processing task, there was no such general concurrence cost. Rather, there was a prioritization effect in dual-task performance for both tasks, irrespective of age, in which performance levels depended on the relative emphasis assigned to memory versus processing. This prioritization effect was large, albeit with a large residual in performance. The findings place important constraints on both working memory theory and our understanding of how working memory changes across the adult lifespan. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The Sources of Dual-task Costs in Multisensory Working Memory Tasks

We investigated the sources of dual-task costs arising in multisensory working memory (WM) tasks, where stimuli from different modalities have to be simultaneously maintained. Performance decrements relative to unimodal single-task baselines have been attributed to a modality-unspecific central WM store, but such costs could also reflect increased demands on central executive processes involved in dual-task coordination. To compare these hypotheses, we asked participants to maintain two, three, or four visual items. Unimodal trials, where only this visual task was performed, and bimodal trials, where a concurrent tactile WM task required the additional maintenance of two tactile items, were randomly intermixed. We measured the visual and tactile contralateral delay activity (CDA/tCDA components) as markers of WM maintenance in visual and somatosensory areas. There were reliable dual-task costs, as visual CDA components were reduced in size and visual WM accuracy was impaired on bimodal relative to unimodal trials. However, these costs did not depend on visual load, which caused identical CDA modulations in unimodal and bimodal trials, suggesting that memorizing tactile items did not reduce the number of visual items that could be maintained. Visual load did not also affect tCDA amplitudes. These findings indicate that bimodal dual-task costs do not result from a competition between multisensory items for shared storage capacity. Instead, these costs reflect generic limitations of executive control mechanisms that coordinate multiple cognitive processes in dual tasks. Our results support hierarchical models of WM, where distributed maintenance processes with modality-specific capacity limitations are controlled by a central executive mechanism.

A Neural Mechanism for Surprise-related Interruptions of Visuospatial Working Memory

Surprising perceptual events recruit a fronto-basal ganglia mechanism for inhibition, which suppresses motor activity following surprise. A recent study found that this inhibitory mechanism also disrupts the maintenance of verbal working memory (WM) after surprising tones. However, it is unclear whether this same mechanism also relates to surprise-related interruptions of non-verbal WM. We tested this hypothesis using a change-detection task, in which surprising tones impaired visuospatial WM. Participants also performed a stop-signal task (SST). We used independent component analysis and single-trial scalp-electroencephalogram to test whether the same inhibitory mechanism that reflects motor inhibition in the SST relates to surprise-related visuospatial WM decrements, as was the case for verbal WM. As expected, surprising tones elicited activity of the inhibitory mechanism, and this activity correlated strongly with the trial-by-trial level of surprise. However, unlike for verbal WM, the activity of this mechanism was unrelated to visuospatial WM accuracy. Instead, inhibition-independent activity that immediately succeeded the inhibitory mechanism was increased when visuospatial WM was disrupted. This shows that surprise-related interruptions of visuospatial WM are not effected by the same inhibitory mechanism that interrupts verbal WM, and instead provides evidence for a 2-stage model of distraction.

Tone series and the nature of working memory capacity development

Recent advances in understanding visual working memory, the limited information held in mind for use in ongoing processing, are extended here to examine auditory working memory development. Research with arrays of visual objects has shown how to distinguish the capacity, in terms of the number of objects retained, from the precision of the object representations. We adapt the technique to sequences of nonmusical tones, in an investigation including children (6-13 years, N = 84) and adults (26-50 years, N = 31). For each series of 1 to 4 tones, the participant responded by using an 80-choice scale to try to reproduce the tone at a queried serial position. Despite the much longer-lasting usefulness of sensory memory for tones compared with visual objects, the observed tone capacity was similar to previous findings for visual capacity. The results also constrain theories of childhood working memory development, indicating increases with age in both the capacity and the precision of the tone representations, similar to the visual studies, rather than age differences in time-based memory decay. The findings, including patterns of correlations between capacity, precision, and some auxiliary tasks and questionnaires, establish capacity and precision as dissociable processes and place important constraints on various hypotheses of working memory development. (PsycINFO Database Record

Development of the ability to combine visual and acoustic information in working memory

Presentation of two kinds of materials in working memory (visual and acoustic), with the requirement to attend to one or both modalities, poses an interesting case for working memory development because competing predictions can be formulated. In two experiments, we assessed such predictions with children 7-13 years old and adults. With development, the ability to hold more information in the focus of attention could lead to an increase in the size of the trade-off between modalities; if attention can hold A items during unimodal-attention trials, then on average attention should hold A/2 of those same items during bimodal-attention trials. If A increases with age, so would the dual-task cost, A/2. The results clearly ruled out that possibility. It was the modality- or code-specific components of working memory that improved with age and not the central component. We discuss various mechanisms that could have produced these results, including alternative attention-based mechanisms. The findings point to a rich field for continued research.

The influence of lapses of attention on working memory capacity

In three experiments, the influence of lapses of attention on working memory (WM) capacity measures was examined. Participants performed various change detection tasks while also reporting whether they were focused on the current task or whether they were unfocused and mind-wandering. Participants reported that they were mind-wandering roughly 27% of the time, and when participants reported mind-wandering, their performance was worse compared to when they reported being on-task. Low WM capacity individuals reported more mind-wandering and lapses of attention than high WM capacity individuals, and mind-wandering and filtering abilities were shown to make independent contributions to capacity estimates. These results provide direct support for the notion that the ability to focus attention on-task and prevent lapses of attention is an important contributor to performance on measures of WM capacity.

The effects of long-term stress on neural dynamics of working memory processing: An investigation using ERP

This study examined the neural dynamics of working memory (WM) processing under long-term stress. Forty participants who had been exposed to a long period of major exam preparation (six months) and twenty-one control participants performed a numerical n-back task (n = 1, 2) while electroencephalograms were recorded. Psychological and endocrinal measurements confirmed significantly higher levels of long-term stress for participants in the exam group. The exam group showed significantly increased P2 amplitude in the frontal-central sites in the 1-back and 2-back conditions, whereas other ERP components, including the P1, N1 and P3 and behavioral performance, were unchanged. Notably, the P2 effect was most pronounced in participants in the exam group who reported perceiving high levels of stress. The perceived stress scores positively correlated with the P2 amplitude in the 1-back and 2-back conditions. These results suggest that long-term stress has an impact on attention and the initiation of the updating process in WM.

Resource allocation models of auditory working memory

Auditory working memory (WM) is the cognitive faculty that allows us to actively hold and manipulate sounds in mind over short periods of time. We develop here a particular perspective on WM for non-verbal, auditory objects as well as for time based on the consideration of possible parallels to visual WM. In vision, there has been a vigorous debate on whether WM capacity is limited to a fixed number of items or whether it represents a limited resource that can be allocated flexibly across items. Resource allocation models predict that the precision with which an item is represented decreases as a function of total number of items maintained in WM because a limited resource is shared among stored objects. We consider here auditory work on sequentially presented objects of different pitch as well as time intervals from the perspective of dynamic resource allocation. We consider whether the working memory resource might be determined by perceptual features such as pitch or timbre, or bound objects comprising multiple features, and we speculate on brain substrates for these behavioural models. This article is part of a Special Issue entitled SI: Auditory working memory.

Effect of working memory load on electrophysiological markers of visuospatial orienting in a spatial cueing task simulating a traffic situation

Visuospatial attentional orienting has typically been studied in abstract tasks with low ecological validity. However, real-life tasks such as driving require allocation of working memory (WM) resources to several subtasks over and above orienting in a complex sensory environment. The aims of this study were twofold: firstly, to establish whether electrophysiological signatures of attentional orienting commonly observed under simplified task conditions generalize to a more naturalistic task situation with realistic-looking stimuli, and, secondly, to assess how these signatures are affected by increased WM load under such conditions. Sixteen healthy participants performed a dual task consisting of a spatial cueing paradigm and a concurrent verbal memory task that simulated aspects of an actual traffic situation. Behaviorally, we observed a load-induced detriment of sensitivity to targets. In the EEG, we replicated orienting-related alpha lateralization, the lateralized ERPs ADAN, EDAN, and LDAP, and the P1-N1 attention effect. When WM load was high (i.e., WM resources were reduced), lateralization of oscillatory activity in the lower alpha band was delayed. In the ERPs, we found that ADAN was also delayed, while EDAN was absent. Later ERP correlates were unaffected by load. Our results show that the findings in highly controlled artificial tasks can be generalized to spatial orienting in ecologically more valid tasks, and further suggest that the initiation of spatial orienting is delayed when WM demands of an unrelated secondary task are high.

Visual selective attention is equally functional for individuals with low and high working memory capacity: evidence from accuracy and eye movements

Selective attention and working memory capacity (WMC) are related constructs, but debate about the manner in which they are related remains active. One elegant explanation of variance in WMC is that the efficiency of filtering irrelevant information is the crucial determining factor, rather than differences in capacity per se. We examined this hypothesis by relating WMC (as measured by complex span tasks) to accuracy and eye movements during visual change detection tasks with different degrees of attentional filtering and allocation requirements. Our results did not indicate strong filtering differences between high- and low-WMC groups, and where differences were observed, they were counter to those predicted by the strongest attentional filtering hypothesis. Bayes factors indicated evidence favoring positive or null relationships between WMC and correct responses to unemphasized information, as well as between WMC and the time spent looking at unemphasized information. These findings are consistent with the hypothesis that individual differences in storage capacity, not only filtering efficiency, underlie individual differences in working memory.

Central and peripheral components of working memory storage

This study reexamines the issue of how much of working memory storage is central, or shared across sensory modalities and verbal and nonverbal codes, and how much is peripheral, or specific to a modality or code. In addition to the exploration of many parameters in 9 new dual-task experiments and reanalysis of some prior evidence, the innovations of the present work compared to previous studies of memory for 2 stimulus sets include (a) use of a principled set of formulas to estimate the number of items in working memory and (b) a model to dissociate central components, which are allocated to very different stimulus sets depending on the instructions, from peripheral components, which are used for only 1 kind of material. We consistently find that the central contribution is smaller than was suggested by Saults and Cowan (2007) and that the peripheral contribution is often much larger when the task does not require the binding of features within an object. Previous capacity estimates are consistent with the sum of central plus peripheral components observed here. We consider the implications of the data as constraints on theories of working memory storage and maintenance.

Cross-Modal Decoding of Neural Patterns Associated with Working Memory: Evidence for Attention-Based Accounts of Working Memory

Recent studies suggest common neural substrates involved in verbal and visual working memory (WM), interpreted as reflecting shared attention-based, short-term retention mechanisms. We used a machine-learning approach to determine more directly the extent to which common neural patterns characterize retention in verbal WM and visual WM. Verbal WM was assessed via a standard delayed probe recognition task for letter sequences of variable length. Visual WM was assessed via a visual array WM task involving the maintenance of variable amounts of visual information in the focus of attention. We trained a classifier to distinguish neural activation patterns associated with high- and low-visual WM load and tested the ability of this classifier to predict verbal WM load (high-low) from their associated neural activation patterns, and vice versa. We observed significant between-task prediction of load effects during WM maintenance, in posterior parietal and superior frontal regions of the dorsal attention network; in contrast, between-task prediction in sensory processing cortices was restricted to the encoding stage. Furthermore, between-task prediction of load effects was strongest in those participants presenting the highest capacity for the visual WM task. This study provides novel evidence for common, attention-based neural patterns supporting verbal and visual WM.

Estimating working memory capacity for lists of nonverbal sounds

Working memory (WM) capacity limit has been extensively studied in the domains of visual and verbal stimuli. Previous studies have suggested a fixed WM capacity of typically about three or four items, on the basis of the number of items in working memory reaching a plateau after several items as the set size increases. However, the fixed WM capacity estimate appears to rely on categorical information in the stimulus set (Olsson & Poom Proceedings of the National Academy of Sciences 102:8776-8780, 2005). We designed a series of experiments to investigate nonverbal auditory WM capacity and its dependence on categorical information. Experiments 1 and 2 used simple tones and revealed capacity limit of up to two tones following a 6-s retention interval. Importantly, performance was significantly higher at set sizes 2, 3, and 4 when the frequency difference between target and test tones was relatively large. In Experiment 3, we added categorical information to the simple tones, and the effect of tone change magnitude decreased. Maximal capacity for each individual was just over three sounds, in the range of typical visual procedures. We propose that two types of information, categorical and detailed acoustic information, are kept in WM and that categorical information is critical for high WM performance.

Distraction Effects of Smoking Cues in Antismoking Messages: Examining Resource Allocation to Message Processing as a Function of Smoking Cues and Argument Strength

Findings from previous studies on smoking cues and argument strength in antismoking messages have shown that the presence of smoking cues undermines the persuasiveness of antismoking public service announcements (PSAs) with weak arguments. This study conceptualized smoking cues (i.e., scenes showing smoking-related objects and behaviors) as stimuli motivationally relevant to the former smoker population and examined how smoking cues influence former smokers' processing of antismoking PSAs. Specifically, by defining smoking cues and the strength of antismoking arguments in terms of resource allocation, this study examined former smokers' recognition accuracy, memory strength, and memory judgment of visual (i.e., scenes excluding smoking cues) and audio information from antismoking PSAs. In line with previous findings, the results of the study showed that the presence of smoking cues undermined former smokers' encoding of antismoking arguments, which includes the visual and audio information that compose the main content of antismoking messages.

Differential reinforcement and resistance to change of divided-attention performance

Behavioral momentum theory provides a framework for understanding how conditions of reinforcement influence instrumental response strength under conditions of disruption (i.e., resistance to change). The present experiment examined resistance to change of divided-attention performance when different overall probabilities of reinforcement were arranged across two components of a multiple schedule. Pigeons responded in a delayed-matching-to-sample procedure with compound samples (color + line orientation) and element comparisons (two colors or two line orientations). Reinforcement ratios of 1:9, 1:1, and 9:1 for accurate matches on the two types of comparison trials were examined across conditions using reinforcement probabilities (color/lines) of .9/.1, .5/.5, and .1/.9 in the rich component and .18/.02, .1/.1, and .02/.18 in the lean component. Relative accuracy with color and line comparisons was an orderly function of relative reinforcement, but this relation did not depend on the overall rate of reinforcement between components. The resistance to change of divided-attention performance was greater for both trial types in the rich component with presession feeding and extinction, but not with decreases in sample duration. These findings suggest promise for the applicability of quantitative models of operant behavior to divided-attention performance, but they highlight the need to further explore conditions impacting the resistance to change of attending.

Models of verbal working memory capacity: what does it take to make them work?

Theories of working memory (WM) capacity limits will be more useful when we know what aspects of performance are governed by the limits and what aspects are governed by other memory mechanisms. Whereas considerable progress has been made on models of WM capacity limits for visual arrays of separate objects, less progress has been made in understanding verbal materials, especially when words are mentally combined to form multiword units or chunks. Toward a more comprehensive theory of capacity limits, we examined models of forced-choice recognition of words within printed lists, using materials designed to produce multiword chunks in memory (e.g., leather brief case). Several simple models were tested against data from a variety of list lengths and potential chunk sizes, with test conditions that only imperfectly elicited the interword associations. According to the most successful model, participants retained about 3 chunks on average in a capacity-limited region of WM, with some chunks being only subsets of the presented associative information (e.g., leather brief case retained with leather as one chunk and brief case as another). The addition to the model of an activated long-term memory component unlimited in capacity was needed. A fixed-capacity limit appears critical to account for immediate verbal recognition and other forms of WM. We advance a model-based approach that allows capacity to be assessed despite other important processing contributions. Starting with a psychological-process model of WM capacity developed to understand visual arrays, we arrive at a more unified and complete model.

Cross-domain interference costs during concurrent verbal and spatial serial memory tasks are asymmetric

Some evidence suggests that memory for serial order is domain-general. Evidence also points to asymmetries in interference between verbal and visual-spatial tasks. We confirm that concurrently remembering verbal and spatial serial lists provokes substantial interference compared with remembering a single list, but we further investigate the impact of this interference throughout the serial position curve, where asymmetries are indeed apparent. A concurrent verbal order memory task affects spatial memory performance throughout the serial positions of the list, but performing a spatial order task affects memory for the verbal serial list only for early list items; in the verbal task only, the final items are unaffected by a concurrent task. Adding suffixes eliminates this asymmetry, resulting in impairment throughout the list for both tasks. These results suggest that domain-general working memory resources may be supplemented with resources specific to the verbal domain, but perhaps not with equivalent spatial resources.

WoMMBAT: A user interface for hierarchical Bayesian estimation of working memory capacity

The change detection paradigm has become an important tool for researchers studying working memory. Change detection is especially useful for studying visual working memory, because recall paradigms are difficult to employ in the visual modality. Pashler (Perception & Psychophysics, 44, 369–378, 1988) and Cowan (Behavioral and Brain Sciences, 24, 87–114, 2001) suggested formulas for estimating working memory capacity from change detection data. Although these formulas have become widely used, Morey (Journal of Mathematical Psychology, 55, 8–24, 2011) showed that the formulas suffer from a number of issues, including inefficient use of information, bias, volatility, uninterpretable parameter estimates, and violation of ANOVA assumptions. Morey presented a hierarchical Bayesian extension of Pashler’s and Cowan’s basic models that mitigates these issues. Here, we present WoMMBAT (Working Memory Modeling using Bayesian Analysis Techniques) software for fitting Morey’s model to data. WoMMBAT has a graphical user interface, is freely available, and is cross-platform, running on Windows, Linux, and Mac operating systems.

How to measure working memory capacity in the change detection paradigm

Although the measurement of working memory capacity is crucial to understanding working memory and its interaction with other cognitive faculties, there are inconsistencies in the literature on how to measure capacity. We address the measurement in the change detection paradigm, popularized by Luck and Vogel (Nature, 390, 279–281, 1997). Two measures for this task—from Pashler (Perception & Psychophysics, 44, 369–378, 1988) and Cowan (The Behavioral and Brain Sciences, 24, 87–114, 2001), respectively—have been used interchangeably, even though they may yield qualitatively different conclusions. We show that the choice between these two measures is not arbitrary. Although they are motivated by the same underlying discrete-slots working memory model, each is applicable only to a specific task; the two are never interchangeable. In the course of deriving these measures, we discuss subtle but consequential flaws in the underlying discrete-slots model. These flaws motivate revision in the modal model and capacity measures.

Can the focus of attention accommodate multiple, separate items?

Researchers of working memory currently debate capacity limits of the focus of attention, the proposed mental faculty in which items are most easily accessed. Cowan (1999) suggested that its capacity is about 4 chunks, whereas others have suggested that its capacity is only 1 chunk. Recently, Oberauer and Bialkova (2009) found evidence that 2 items could reside in the focus of attention, but only because they were combined into a single chunk. We modified their experimental procedure, which depends on a pattern of switch costs, to obtain a situation in which chunking was not likely to occur (i.e., each item remained a separate chunk) and still obtained results consistent with a capacity of at least 2 items. Therefore, either the focus of attention can hold multiple chunks or the switch cost logic must be reconsidered.

The focus of attention as observed in visual working memory tasks: making sense of competing claims

Recent behavioral and neuroscientific evidence speaks to the question of whether the human focus of attention is limited to a single item or can accommodate several items. This issue is fundamental to an understanding of the nature of human cognition and brain function. Here I review evidence from visual working memory tasks and suggest that it supports the concept of a focus of attention that can include several items at once as a core vehicle of working memory, regardless of the stimulus modality. One brain area in particular, the left intraparietal sulcus (IPS), seems critically important in the network underlying the focus of attention as a working memory storage mechanism. This view is reconciled with evidence previously taken to indicate that the focus of attention only includes a single item at a time, which is reinterpreted here.