Retrieval-practice task affects relationship between working memory capacity and retrieval-induced forgetting

Retrieving a subset of items from memory can cause forgetting of other items in memory, a phenomenon referred to as retrieval-induced forgetting (RIF). Individuals who exhibit greater amounts of RIF have been shown to also exhibit superior working memory capacity (WMC) and faster stop-signal reaction times (SSRTs), results which have been interpreted as suggesting that RIF reflects an inhibitory process that is mediated by the processes of executive control. Across four experiments, we sought to further elucidate this issue by manipulating the way in which participants retrieved items during retrieval practice and examining how the resulting effects of forgetting correlated with WMC (Experiments 1–3) and SSRT (Experiment 4). Significant correlations were observed when participants retrieved items from an earlier study phase (within-list retrieval practice), but not when participants generated items from semantic memory (extra-list retrieval practice). These results provide important new insight into the role of executive-control processes in RIF.     

Reasoning strategies: the role of working memory and verbal-spatial ability

Evidence increasingly suggests individual differences in strategies adopted on reasoning tasks and that these are either verbal-propositional or visuospatial in nature. However, the cognitive foundations of these strategies remain uncertain. Experiment 1 examined the relationship between the use of working memory resources and strategy selection for syllogistic reasoning. Verbal and spatial strategy users did not differ on working memory capacity, but confirmatory factor analysis indicated that while verbal reasoners draw primarily on verbal working memory, spatial reasoners use both this and spatial resources. Experiment 2 investigated the relationship between strategies and verbal and spatial abilities. Although strategy groups were similar in overall ability, regression analysis showed that performance on a spatial ability measure (Vandenberg mental rotation task) predicted syllogistic reasoning performance, but only for spatial strategy users. The findings provide converging evidence that verbal and spatial strategies are underpinned by related differences in fundamental cognitive factors, drawing differentially on the subcomponents of working memory and on spatial ability.     

Individual differences in analytic versus holistic thinking

The authors constructed the Analysis-Holism Scale (AHS) to measure analytic versus holistic thinking tendency. In Study 1, using exploratory and confirmatory factor analysis, a 24-item scale was developed. In Study 2, convergent and discriminant validities were tested. In Studies 3 and 4, the known-group difference validity was examined by comparing scores on the AHS of Americans and Koreans (Study 3) and of Korean students of Oriental medicine and Korean students of non-Oriental medicine majors (Study 4). Results of Studies 3 and 4 show that Koreans and Korean students of Oriental medicine scored higher on the AHS than did Americans and Korean students of non-Oriental medicine majors, respectively. Studies 5 and 6 tested predictive validity by examining associations of the AHS with performances on two cognitive tasks (categorization and causal reasoning). Data analysis shows that those with high scores on the AHS displayed the holistic pattern of performances on each task more than did those with low scores.     

Exploring evaluative conditioning using a working memory task

Johnsrude, Owen, Zhao, and White (1999) demonstrated that evaluative conditioning (EC) can occur even while participants conduct a working memory task. This is consistent with claims that EC can occur outside awareness, and hence is an automatic process. In their study, three abstract patterns were paired differentially with a candy reinforcer: 90, 50, or 10%. On reinforced trials a red ball was presented in one of three locations on a computer screen. Participants were instructed to keep a tally for each location. We argue that if EC is automatic, then it will not consume cognitive/attentional resources, and hence co-occurrence of red ball and reinforcer should be irrelevant. Results from four experiments indicate that learning is only evident when the red ball and reinforcer co-occur or when the complexity of the working memory task is reduced. Together, the results suggest that EC is governed by specific attentional constraints on working memory. This interpretation questions the automatic nature of EC.     

The role of working memory capacity and interference resolution mechanisms in task switching

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response–distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. A total of 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response–distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores, which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching.     

The nature of inhibition in a working memory search task

Inhibition is one of the key processes that regulate working memory (WM) activity. The main research question concerned the nature of inhibition of highlighted information in WM. The study was designed to examine two competing hypotheses. The first assumed that inhibition is carried out by deletion of irrelevant information from the focus of attention (cognitive inhibition account). An alternative hypothesis assumed that it is the response to a correctly recognised stimulus that is inhibited (effortful response inhibition account). Two experiments with a spatial modification of the WM serial search task were conducted wherein two factors were manipulated: serial order of the items, and distance from the central fixation point. In both experiments, higher response time was correlated with a smaller distance from the fixation point. The inhibited items were recognised equally efficiently or better than the uninhibited items. The results support the effortful response inhibition account over the cognitive inhibition account.     

Minimal use of working memory in a scene comparison task

Eye movement behaviour in hand-eye tasks suggests a preference for a “just in time” processing strategy that minimizes the use of working memory. In the present study, a scene comparison task was introduced to determine whether the preference holds when the task is primarily visual and when more complex naturalistic scenes are used as stimuli. In two experiments, participants made same or different judgements in response to simultaneously presented pairs of scenes that were identical or differed by one object. The number of fixations per scene glance and the number of fixations intervening between glances to corresponding objects suggest that frequently one object at a time is encoded and maintained in visual working memory. The same pattern of results was observed in a third experiment using word and object arrays. Overall, the results suggest a strong general bias toward minimal use of visual working memory in complex visual tasks.     

The persistence of thought: evidence for a role of working memory in the maintenance of task-unrelated thinking

Tasks that tax working memory (WM) have consistently been found to decrease mind wandering. These findings may indicate that maintenance of mind wandering requires WM resources, such that mind wandering cannot persist when WM resources are being consumed by a task. An alternative explanation for these findings, however, is that mind wandering persists without the support of WM but is nonetheless decreased during any demanding task because good task performance requires that attention be restricted from task-unrelated thought (TUT). The present study tested these two competing theories by investigating whether individuals with greater WM resources mind-wander more during an undemanding task, as would be predicted only by the theory that WM supports TUT. We found that individuals with higher WM capacity reported more TUT in undemanding tasks, which suggests that WM enables the maintenance of mind wandering.     

Roles of working memory capacity and long-term working memory skill in complex task performance

In the present research, we examined the relative roles of domain-general and domain-specific individual difference characteristics in complex cognitive task performance. Specifically, we examined the impact both of working memory (WM) capacity and of acquired skills used to encode presented information in an accessible form in long-term working memory (LTWM) on performance in a complex aviation task environment. Measures of WM capacity and LTWM skill served as performance predictors. A criterion measure of task performance was related to the predictor measures. The results indicated that an increase in LTWM skill decreases the role of WM capacity as the determinant of complex task performance, although both measures are important performance predictors. We discuss how the two distinct WM constructs coexist and interact to support complex task performance.     

Anisomycin impairs long-term working memory in a delayed alternation task

A long-term temporal component of working memory of rats trained on the radial maze has been shown to be susceptible to disruption by the protein synthesis inhibitor, anisomycin. It is not clear whether protein synthesis played a role in working memory because accurate performance on the radial maze required the storage of a large amount of information, or because the information was to be held in store for relatively long periods of time. This experiment tested these hypotheses by assessing the effect of anisomycin on choice accuracy in a comparatively simple spatial delayed alternation task. Results indicate that under the present training conditions, protein involvement in working memory is related more to the length of the retention interval than to the amount of information retained.     

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.     

What's working in working memory: a role for the Central Executive

Two experiments are reported which seek to explore the nature of the Central Executive of Baddeley's (Baddeley and Hitch, 1974) model of working memory. Experiment 1 uses a dual task methodology to compare performance on two storage tasks, making use of the two slave systems, the Phonological Loop (PL) and the Visuo-Spatial Scratch Pad (VSSP). Results suggest that storage can be thought of as based on the use of slave system independent resources. Experiment 2 uses a similar approach to compare performance on 2 processing tasks, again one PL based, the other VSSP based. These results suggest that processing is based on a central, shared set of resources. The two experiments support both a multiple resources model of working memory and more specifically identify a role for the Central Executive.     

Neural substrates of successful working memory and long-term memory formation in a relational spatial memory task

Working memory (WM) tasks may involve brain activation actually implicated in long-term memory (LTM). In order to disentangle these two memory systems, we employed a combined WM/LTM task, using a spatial relational (object-location) memory paradigm and analyzed which brain areas were associated with successful performance for either task using fMRI. Critically, we corrected for the performance on the respective memory task when analyzing subsequent memory effects. The WM task consisted of a delayed-match-to-sample task assessed in an MRI scanner. Each trial consisted of an indoor or outdoor scene in which the exact configuration of four objects had to be remembered. After a short delay (7–13 s), the scene was presented from a different angle and spatial recognition for two objects was tested. After scanning, participants received an unexpected subsequent recognition memory (LTM) task, where the two previously unprobed objects were tested. Brain activity during encoding, delay phase and probe phase was analyzed based on WM and LTM performance. Results showed that successful WM performance, when corrected for LTM performance, was associated with greater activation in the inferior frontal gyrus and left fusiform gyrus during the early stage of the maintenance phase. A correct decision during the WM probe was accompanied by greater activation in a wide network, including bilateral hippocampus, right superior parietal gyrus and bilateral insula. No voxels exhibited supra-threshold activity during the encoding phase, and we did not find any differential activity for correct versus incorrect trials in the WM task when comparing LTM correct versus LTM incorrect trials.     

The role of phonological and executive working memory resources in simple arithmetic strategies

The current study investigated the role of the central executive and the phonological loop in arithmetic strategies to solve simple addition problems (Experiment 1) and simple subtraction problems (Experiment 2). The choice/no-choice method was used to investigate strategy execution and strategy selection independently. The central executive was involved in both retrieval and procedural strategies, but played a larger role in the latter than in the former. Active phonological processes played a role in procedural strategies only. Passive phonological resources, finally, were only needed when counting was used to solve subtraction problems. No effects of working memory load on strategy selection were observed.     

A group-administered lag task as a measure of working memory

The purpose of the present studies was to evaluate the utility of a group-administered version of the n-back, or lag task. Experiments 1 and 2 describe the construction of the task and reveal that the modified lag task (MLT) produces the same performance trends as have been observed in individually administered versions of the lag task; performance decreased significantly as lag conditions increased in difficulty. Experiments 3 and 4 established convergent validity by comparing the MLT to another common working memory task, the operation-word span task, as well as the updated version of this task, the automatic operation span task. The results showed that MLT performance was significantly correlated to scores on both measures. These experiments provide important details about the MLT as a measure of working memory, in a group- or individual-administration setting.     

Classifying retrieval strategies as a function of working memory

Strategy selection may help explain performance differences between individuals with high working memory capacity (HWMs) and low working memory capacity (LWMs) (Budd, Whitney, & Turley, (Memory & Cognition, 23, 735–748 1995); Cokely, Kelley, & Gilchrist, (Psychonomic Bulletin & Review, 13, 991–997 2006). We compared the independent and spontaneous strategy use of HWMs and LWMs during a category fluency (retrieval) task that required participants to retrieve animal names. HWMs were more successful at the fluency task under normal conditions, but under increased cognitive load, there were no WM-related performance differences. One strategy (i.e., retrieving animals according to their scientific classification) significantly aided performance, irrespective of cognitive load. Under normal conditions, HWMs were more likely to use the effective strategy; however, under load, WM did not predict strategy use. Use of the classification strategy was more strongly related to retrieval performance than was WM. These results suggest that retrieval strategy use is related to WM capacity, and that employing a successful strategy may make up for WM disadvantages during a demanding retrieval task.     

Encoding strategies in self-initiated visual working memory

During a typical day, visual working memory (VWM) is recruited to temporarily maintain visual information. Although individuals often memorize external visual information provided to them, on many other occasions they memorize information they have constructed themselves. The latter aspect of memory, which we term self-initiated WM, is prevalent in everyday behavior but has largely been overlooked in the research literature. In the present study we employed a modified change detection task in which participants constructed the displays they memorized, by selecting three or four abstract shapes or real-world objects and placing them at three or four locations in a circular display of eight locations. Half of the trials included identical targets that participants could select. The results demonstrated consistent strategies across participants. To enhance memory performance, participants reported selecting abstract shapes they could verbalize, but they preferred real-world objects with distinct visual features. Furthermore, participants constructed structured memory displays, most frequently based on the Gestalt organization cue of symmetry, and to a lesser extent on cues of proximity and similarity. When identical items were selected, participants mostly placed them in close proximity, demonstrating the construction of configurations based on the interaction between several Gestalt cues. The present results are consistent with recent findings in VWM, showing that memory for visual displays based on Gestalt organization cues can benefit VWM, suggesting that individuals have access to metacognitive knowledge on the benefit of structure in VWM. More generally, this study demonstrates how individuals interact with the world by actively structuring their surroundings to enhance performance.     

Simon says: Reliability and the role of working memory and attentional control in the Simon task

TheSimon effect refers to the observation that subjects identify targets (e.g., colors) faster when the irrelevant spatial location of the target corresponds to the location of the response key. Theoretical accounts of the Simon effect typically explain performance in terms of automatic and controlled processes. Furthermore, the relative contributions of automatic and controlled processes are held to change as a function of the proportion of compatible to incompatible trials (compatibility proportion). Data are presented demonstrating that the reliability of the Simon effect, indexed by correlating its magnitude within subjects across blocks of trials, varied substantially as a function of the compatibility proportion. When the compatibility proportion was high, so was reliability. When the compatibility proportion was low, reliability was low as well. The results are discussed in terms of the relative reliability of automatic and controlled processes and the role of working memory and attentional control in goal maintenance.     

The concurrent validity of the N-back task as a working memory measure

The N-back task is used extensively in literature as a working memory (WM) paradigm and it is increasingly used as a measure of individual differences. However, not much is known about the psychometric properties of this task and the current study aims to shed more light on this issue. We first review the current literature on the psychometric properties of the N-back task. With three experiments using task variants with different stimuli and load levels, we then investigate the nature of the N-back task by investigating its relationship to WM, and its role as an inter-individual difference measure. Consistent with previous literature, our data suggest that the N-back task is not a useful measure of individual differences in WM, partly because of its insufficient reliability. Nevertheless, the task seems to be useful for experimental research in WM and also well predicts inter-individual differences in other higher cognitive functions, such as fluid intelligence, especially when used at higher levels of load.     

Training the removal of negative information from working memory: A preliminary investigation of a working memory bias modification task

Rumination in depressed adults is associated with a bias toward retaining negative information in working memory. We developed a task designed to modify this cognitive bias by having subjects repeatedly practice removing negative words from working memory, thereby enabling them to retain positive and neutral words. To assess the efficacy of this task, we recruited 60 adults who reported elevated repetitive negative thought (RNT) and randomly assigned them to receive a single administration of either the working memory bias modification (WMBM) task or a control task. Subjects in the WMBM condition exhibited greater reduction in proactive interference for negative information than did those in the control condition. These results suggest that the WMBM task reduces biased retention of negative information in working memory and, thus, may be useful in investigating the possible causal role of this cognitive bias in RNT or depression.