Maintaining binding in working memory: comparing the effects of intentional goals and incidental affordances

Much research on memory for binding depends on incidental measures. However, if encoding associations benefits from conscious attention, then incidental measures of binding memory might not yield a sufficient understanding of how binding is accomplished. Memory for letters and spatial locations was compared in three within-participants tasks, one in which binding was not afforded by stimulus presentation, one in which incidental binding was possible, and one in which binding was explicitly to be remembered. Some evidence for incidental binding was observed, but unique benefits of explicit binding instructions included preserved discrimination as set size increased and drastic reduction in false alarms to lures that included a new spatial location and an old letter. This suggests that substantial cognitive benefits, including enhanced memory for features themselves, might occur through intentional binding, and that incidental measures of binding might not reflect these advantages.     

Episodic future thought: Contributions from working memory

The ability to imagine hypothetical events in one’s personal future is thought to involve a number of constituent cognitive processes. We investigated the extent to which individual differences in working memory capacity contribute to facets of episodic future thought. College students completed simple and complex measures of working memory and were cued to recall autobiographical memories and imagine future autobiographical events consisting of varying levels of specificity (i.e., ranging from generic to increasingly specific and detailed events). Consistent with previous findings, future thought was related to analogous measures of autobiographical memory, likely reflecting overlapping cognitive factors supporting both past and future thought. Additionally, after controlling for autobiographical memory, residual working memory variance independently predicted future episodic specificity. We suggest that when imagining future events, working memory contributes to the construction of a single, coherent, future event depiction, but not to the retrieval or elaboration of event details.     

Feature binding and attention in working memory: A resolution of previous contradictory findings

We aimed to resolve an apparent contradiction between previous experiments from different laboratories, using dual-task methodology to compare effects of a concurrent executive load on immediate recognition memory for colours or shapes of items or their colour–shape combinations. Results of two experiments confirmed previous evidence that an irrelevant attentional load interferes equally with memory for features and memory for feature bindings. Detailed analyses suggested that previous contradictory evidence arose from limitations in the way recognition memory was measured. The present findings are inconsistent with an earlier suggestion that feature binding takes place within a multimodal episodic buffer Baddeley, (2000 Baddeley, A. D. 2000. The episodic buffer: A new component of working memory?. Trends in Cognitive Sciences, 4(11): 417–423. (doi:10.1016/S1364-6613(00)01538-2)[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and support a subsequent account in which binding takes place automatically prior to information entering the episodic buffer Baddeley, Allen, & Hitch, (2011 Baddeley, A. D., Allen, R. J. and Hitch, G. J. 2011. Binding in visual working memory: The role of the episodic buffer. Neuropsychologia, 49: 1393–1400. (doi:10.1016/j.neuropsychologia.2010.12.042)[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). Methodologically, the results suggest that different measures of recognition memory performance (A′, d′, corrected recognition) give a converging picture of main effects, but are less consistent in detecting interactions. We suggest that this limitation on the reliability of measuring recognition should be taken into account in future research so as to avoid problems of replication that turn out to be more apparent than real.     

The role of the episodic buffer in working memory for language processing

A body of work has accumulated to show that the cognitive process of binding information from different mnemonic and sensory sources as well as in different linguistic modalities can be fractionated from general executive functions in working memory both functionally and neurally. This process has been defined in terms of the episodic buffer (Baddeley in Trends Cogn Sci 4(11):417–423, 2000). This paper considers behavioural, neuropsychological and neuroimaging data that elucidate the role of the episodic buffer in language processing. We argue that the episodic buffer seems to be truly multimodal in function and that while formation of unitary multidimensional representations in the episodic buffer seems to engage posterior neural networks, maintenance of such representations is supported by frontal networks. Although, the episodic buffer is not necessarily supported by executive processes and seems to be supported by different neural networks, it may operate in tandem with the central executive during effortful language processing. There is also evidence to suggest engagement of the phonological loop during buffer processing. The hippocampus seems to play a role in formation but not maintenance of representations in the episodic buffer of working memory.     

A structural analysis of working memory and related cognitive skills in young children

The aim of this study was to investigate the functional organisation of working memory and related cognitive abilities in young children. A sample of 633 children aged between 4 and 6 years were tested on measures of verbal short-term memory, complex memory span, sentence repetition, phonological awareness, and nonverbal ability. The measurement model that provided the best fit of the data incorporates constructs that correspond to the central executive, phonological loop, and episodic buffer subcomponents of working memory, plus distinct but associated constructs associated with phonological awareness and nonverbal ability.     

Attention is required for maintenance of feature binding in visual working memory

Working memory and attention are intimately connected. However, understanding the relationship between the two is challenging. Currently, there is an important controversy about whether objects in working memory are maintained automatically or require resources that are also deployed for visual or auditory attention. Here we investigated the effects of loading attention resources on precision of visual working memory, specifically on correct maintenance of feature-bound objects, using a dual-task paradigm. Participants were presented with a memory array and were asked to remember either direction of motion of random dot kinematograms of different colour, or orientation of coloured bars. During the maintenance period, they performed a secondary visual or auditory task, with varying levels of load. Following a retention period, they adjusted a coloured probe to match either the motion direction or orientation of stimuli with the same colour in the memory array. This allowed us to examine the effects of an attention-demanding task performed during maintenance on precision of recall on the concurrent working memory task. Systematic increase in attention load during maintenance resulted in a significant decrease in overall working memory performance. Changes in overall performance were specifically accompanied by an increase in feature misbinding errors: erroneous reporting of nontarget motion or orientation. Thus in trials where attention resources were taxed, participants were more likely to respond with nontarget values rather than simply making random responses. Our findings suggest that resources used during attention-demanding visual or auditory tasks also contribute to maintaining feature-bound representations in visual working memory—but not necessarily other aspects of working memory.     

Movement and visual coding: the structure of visuo-spatial working memory

The influential model of verbal working memory (WM) introduced by Baddeley and Hitch (Recent advances in learning and motivation. Academic, New York, 1974) comprised three interacting component parts; an executive controller and two subservient systems. The two subservient systems, one underpinning verbal processing and the other underpinning visual processing are themselves subdivided. In the verbal system, a passive phonological store is maintained by an active phonological loop, which is able to rehearse the material in the passive store. The visual working memory system has traditionally been thought of as having a similar architecture with a passive visual store being maintained by an active store, which codes in terms of movement over space. The paper discusses the evidence for this relationship in visuo-spatial WM and concludes that the architecture does not fit well with the experimental literature. A direction for future research is suggested.     

Cognitive and neuropsychological underpinnings of relational and conjunctive working memory binding across age

The ability to form associations (i.e., binding) is critical for memory formation. Recent studies suggest that aging specifically affects relational binding (associating separate features) but not conjunctive binding (integrating features within an object). Possibly, this dissociation may be driven by the spatial nature of the studies so far. Alternatively, relational binding may simply require more attentional resources. We assessed relational and conjunctive binding in three age groups and we included an interfering task (i.e., an articulatory suppression task). Binding was examined in a working memory (WM) task using non-spatial features: shape and colour. Thirty-one young adults (mean age = 22.35), 30 middle-aged adults (mean age = 54.80) and 30 older adults (mean age = 70.27) performed the task. Results show an effect of type of binding and an effect of age but no interaction between type of binding and age. The interaction between type of binding and interference was significant. These results indicate that aging affects relational binding and conjunctive binding similarly. However, relational binding is more susceptible to interference than conjunctive binding, which suggests that relational binding may require more attentional resources. We suggest that a general decline in WM resources associated with frontal dysfunction underlies age-related deficits in WM binding.     

Updating of working memory: Lingering bindings

Three experiments investigated proactive interference and proactive facilitation in a memory-updating paradigm. Participants remembered several letters or spatial patterns, distinguished by their spatial positions, and updated them by new stimuli up to 20 times per trial. Self-paced updating times were shorter when an item previously remembered and then replaced reappeared in the same location than when it reappeared in a different location. This effect demonstrates residual memory for no-longer-relevant bindings of items to locations. The effect increased with the number of items to be remembered. With one exception, updating times did not increase, and recall of final values did not decrease, over successive updating steps, thus providing little evidence for proactive interference building up cumulatively.     

The influence of working memory on the anger superiority effect

The anger superiority effect shows that an angry face is detected more efficiently than a happy face. However, it is still controversial whether attentional allocation to angry faces is a bottom-up process or not. We investigated whether the anger superiority effect is influenced by top-down control, especially working memory (WM). Participants remembered a colour and then searched for differently coloured facial expressions. Just holding the colour information in WM did not modulate the anger superiority effect. However, when increasing the probabilities of trials in which the colour of a target face matched the colour held in WM, participants were inclined to direct attention to the target face regardless of the facial expression. Moreover, the knowledge of high probability of valid trials eliminated the anger superiority effect. These results suggest that the anger superiority effect is modulated by top-down effects of WM, the probability of events and expectancy about these probabilities.     

Delineating the contributions of sustained attention and working memory to individual differences in mindfulness

Mindfulness can be deconstructed into two constituent components: present-moment awareness and acceptance. Attention and working memory are theorized to contribute to individual differences in trait mindfulness, although the precise relationship among these constructs remains unclear. The purpose of the present study was to evaluate the association of neurocognitive indices of attention and working memory with a bidimensional trait measure of mindfulness. Fifty-five psychiatrically and neurologically healthy adults completed the Conners Continuous Performance Test, Penn Letter N-back Test, and Philadelphia Mindfulness Scale. Results indicated that present-moment awareness was associated with a response speed variability measure of sustained attention, whereas acceptance was more strongly linked to working memory efficiency, even after accounting for general intellectual ability. These findings suggest that sustained attention and working memory capacities may differentially subserve individual differences in present-moment awareness and acceptance, thereby illuminating our understanding of the cognitive mechanisms which may underlie trait mindfulness.     

Spatiotemporal configuration of memory arrays as a component of VWM representations

Visual working memory (VWM) has been found to support a very limited representation of visual information and yet relatively little is known about the mechanisms that underlie this important cognitive construct. Prior investigations have revealed that VWM performance can be affected by relatively minor changes in the test method as well as the method of encoding. In the present two experiments, we separately investigated these two factors. The results suggest that sequential object displays can improve VWM performance significantly but that a lack of context relatedness between encoding and retrieval impairs performance. This impairment seems to be caused by a mismatch in the spatiotemporal configuration of the memory and test displays, and, importantly, cannot be compensated by selective attention. These findings suggest that spatiotemporal configuration information may be a fundamental component of the information that is stored in VWM as suggested by a number of influential theories.     

An electrophysiological model of working memory performance

Working memory (WM) enables us to keep a limited amount of information in active mode. It is believed that attention refreshes necessary information in WM and prevents their forgetting. Despite a plethora of models offered, it is not fully understood that what factors may be involved in forgetfulness and in the required time for refreshing the information. In this study, an electrophysiological model of WM is proposed that consists of several resistor-capacitor units. Inspired of the “resource capacity theory,” attention as a limited source of energy refreshes the voltage level of these units. According to the “time-based resource sharing theory,” only one of these units is allowed to use the limited source of attention at each moment. The source of attention is shared between active units. This model mimics the pattern of several well-known observations of WM such as the recall interval, the word length, and the serial position effect. Some suggestions have been provided about influencing factors in WM performance. Model parameters give the ability of investigating the possible effect of some other factors on WM performance and also a probable prediction about how much information can we chunk?     

The focus of attention in working memory: Evidence from a word updating task

Three experiments examined the cognitive costs of item switching within working memory with a novel word updating task, thereby extending previous research to the field of linguistic stimuli and linguistic-graphemic updating operations. In Experiments 1 and 2 costs for switching between working memory items were evident on the word level, and they increased with an increasing word set size (Experiment 2). In contrast, a surprisingly similar switch effect on the level of letters was not affected by word set size (Experiment 2). Experiment 3 showed that this effect is not simply based on the need for re-orienting visual spatial attention. To account for the overall picture of results, a recursive model of attentional foci is proposed. Moreover, individual working memory span appears to be associated with the accuracy of item switching, but not with its speed.     

Dissociative style and individual differences in verbal working memory span

Dissociative style is mostly studied as a risk factor for dissociative pathology, but it may also reflect a fundamental characteristic of healthy information processing. Due to the close link between attention and working memory and the previous finding of enhanced attentional abilities with a high dissociative style, a positive relationship was also expected between dissociative style and verbal working memory span. In a sample of 119 psychology students, it was found that the verbal span of the high-dissociative group was about half a word larger than of the medium and low-dissociative groups. It is suggested that dissociative style may be one of only very few individual differences that is directly relevant to consciousness research.     

Oculomotor involvement in spatial working memory is task-specific

Many everyday tasks, such as remembering where you parked, require the capacity to store and manipulate information about the visual and spatial properties of the world. The ability to represent, remember, and manipulate spatial information is known as visuospatial working memory (VSWM). Despite substantial interest in VSWM the mechanisms responsible for this ability remain debated. One influential idea is that VSWM depends on activity in the eye-movement (oculomotor) system. However, this has proved difficult to test because experimental paradigms that disrupt oculomotor control also interfere with other cognitive systems, such as spatial attention. Here, we present data from a novel paradigm that selectively disrupts activation in the oculomotor system. We show that the inability to make eye-movements is associated with impaired performance on the Corsi Blocks task, but not on Arrow Span, Visual Patterns, Size Estimation or Digit Span tasks. It is argued that the oculomotor system is required to encode and maintain spatial locations indicted by a change in physical salience, but not non-salient spatial locations indicated by the meaning of a symbolic cue. This suggestion offers a way to reconcile the currently conflicting evidence regarding the role of the oculomotor system in spatial working memory.     

The role of attention in binding visual features in working memory: Evidence from cognitive ageing

Two experiments were conducted to assess the costs of attentional load during a feature (colour–shape) binding task in younger and older adults. Experiment 1 showed that a demanding backwards counting task, which draws upon central executive/general attentional resources, reduced binding to a greater extent than individual feature memory, but the effect was no greater in older than in younger adults. Experiment 2 showed that presenting memory items sequentially rather than simultaneously, such that items are required to be maintained while new representations are created, selectively affects binding performance in both age groups. Although this experiment exhibited an age-related binding deficit overall, both age groups were affected by the attention manipulation to an equal extent. While a role for attentional processes in colour–shape binding was apparent across both experiments, manipulations of attention exerted equal effects in both age groups. We therefore conclude that age-related binding deficits neither emerge nor are exacerbated under conditions of high attentional load. Implications for theories of visual working memory and cognitive ageing are discussed.     

Depressive thoughts limit working memory capacity in dysphoria

Dysphoria is associated with persistence of attention on mood-congruent information. Longer time attending to mood-congruent information for dysphoric individuals (DIs) detracts from goal-relevant information processing and should reduce working memory (WM) capacity. Study 1 showed that DIs and non-DIs have similar WM capacities. Study 2 embedded depressive information into a WM task. Compared to non-DIs, DIs showed significantly reduced WM capacity for goal-relevant information in this task. Study 3 replicated results from Studies 1 and 2, and further showed that DIs had a significantly greater association between processing speed and recall on the depressively modified WM task compared to non-DIs. The presence of inter-task depressive information leads to DI-related decreased WM capacity. Results suggest dysphoria-related WM capacity deficits when depressive thoughts are present. WM capacity deficits in the presence of depressive thoughts are a plausible mechanism to explain day-to-day memory and concentration difficulties associated with depressed mood.     

Working memory deficits in boys with attention deficit/hyperactivity disorder (ADHD): An examination of orthographic coding and episodic buffer processes

The episodic buffer component of working memory was examined in children with attention deficit/hyperactivity disorder (ADHD) and typically developing peers (TD). Thirty-two children (ADHD = 16, TD = 16) completed three versions of a phonological working memory task that varied with regard to stimulus presentation modality (auditory, visual, or dual auditory and visual), as well as a visuospatial task. Children with ADHD experienced the largest magnitude working memory deficits when phonological stimuli were presented via a unimodal, auditory format. Their performance improved during visual and dual modality conditions but remained significantly below the performance of children in the TD group. In contrast, the TD group did not exhibit performance differences between the auditory- and visual-phonological conditions but recalled significantly more stimuli during the dual-phonological condition. Furthermore, relative to TD children, children with ADHD recalled disproportionately fewer phonological stimuli as set sizes increased, regardless of presentation modality. Finally, an examination of working memory components indicated that the largest magnitude between-group difference was associated with the central executive. Collectively, these findings suggest that ADHD-related working memory deficits reflect a combination of impaired central executive and phonological storage/rehearsal processes, as well as an impaired ability to benefit from bound multimodal information processed by the episodic buffer.     

The personalisation method applied to a working memory task: Evidence of long-term working memory effects

Ericsson and Kintsch (1995) proposed that, in situations of expertise, individuals can overcome working memory limitations by using long-term working memory. It allows a greater capacity than working memory thanks to long-term memory encoding and retrieving. To test this characteristic, an adaptation of Daneman and Carpenter's (1980) reading span was used. To operationalise expertise, the personalisation method (Guida & Tardieu, 2005) was employed. In Experiment 1, a personalised group, which read reading span sentences that mentioned familiar locations, was compared to a nonpersonalised group, which read sentences with unfamiliar locations. In Experiment 2, a personalised group, which read reading span sentences with neutral locations, was encouraged to mentally personalise these locations by thinking about known locations. This group was compared to a nonpersonalised group, which was encouraged to think about unknown locations. The personalised groups were expected to store and retrieve information in long-term memory via long-term working memory more easily than the nonpersonalised groups, which had to count massively on working memory. The results showed that personalisation enhanced reading span and confirmed one implication of the long-term working memory theory: high- and low-reading-span differences could also be due to long-term memory retrieval. Finally, these results are interpreted in terms of interaction between working memory size and long-term memory knowledge, showing that participants with a lower reading span benefited more from high domain knowledge than participants with a higher reading span.