Expressive writing can increase working memory capacity

The effect of emotional disclosure through expressive writing on available working memory (WM) capacity was examined in 2 semester-long experiments. In the first study, 35 freshmen assigned to write about their thoughts and feelings about coming to college demonstrated larger working memory gains 7 weeks later compared with 36 writers assigned to a trivial topic. Increased use of cause and insight words was associated with greater WM improvements. In the second study, students (n = 34) who wrote about a negative personal experience enjoyed greater WM improvements and declines in intrusive thinking compared with students who wrote about a positive experience (n = 33) or a trivial topic (n = 34). The results are discussed in terms of a model grounded in cognitive and social psychological theory in which expressive writing reduces intrusive and avoidant thinking about a stressful experience, thus freeing WM resources.     

Measuring working memory capacity in children using adaptive tasks: Example validation of an adaptive complex span

Working memory tasks designed for children usually present trials in order of ascending difficulty, with testing discontinued when the child fails a particular level. Unfortunately, this procedure comes with a number of issues, such as decreased engagement from high-ability children, vulnerability of the scores to temporary mind-wandering, and large between-subjects variations in number of trials, testing time, and proactive interference. To circumvent these problems, the goal of the present study was to demonstrate the feasibility of assessing working memory using an adaptive testing procedure. The principle of adaptive testing is to dynamically adjust the level of difficulty as the task progresses to match the participant's ability. We used this method to develop an adaptive complex span task (the ACCES) comprising verbal and visuo-spatial subtests. The task presents a fixed number of trials to all participants, allows for partial credit scoring, and can be used with children regardless of ability level. The ACCES demonstrated satisfying psychometric properties in a sample of 268 children aged 8–13 years, confirming the feasibility of using adaptive tasks to measure working memory capacity in children. A free-to-use implementation of the ACCES is provided.     

Converging evidence that stereotype threat reduces working memory capacity

Although research has shown that priming negative stereotypes leads to lower performance among stigmatized individuals, little is understood about the cognitive mechanism that accounts for these effects. Three experiments tested the hypothesis that stereotype threat interferes with test performance because it reduces individuals' working memory capacity. Results show that priming self-relevant negative stereotypes reduces women's (Experiment 1) and Latinos' (Experiment 2) working memory capacity. The final study revealed that a reduction in working memory capacity mediates the effect of stereotype threat on women's math performance (Experiment 3). Implications for future research on stereotype threat and working memory are discussed.     

How a high working memory capacity can increase proactive interference

Previous findings suggested that a high working memory capacity (WMC) is potentially associated with a higher susceptibility to proactive interference (PI) if the latter is measured under high cognitive load. To explain such a finding, we propose to consider susceptibility to PI as a net effect of individual executive processes and the intrinsic potential for PI. With the latter, we refer to the amount of information that is activated at a given time and that has the potential to exert PI subsequently. In two studies deploying generalized linear mixed models, susceptibility to PI was modeled as the decline of performance over trials of a complex span task. The results revealed that a higher WMC was associated with a higher susceptibility to PI. Moreover, the number of stimuli recalled in one trial as a proxy variable for the intrinsic potential for PI negatively affected memory performance in the subsequent trial.     

Restriction of working memory capacity during worry

The authors report the first direct assessment of working memory capacity when people engage in worry. High and low worriers performed a random key-press task while thinking about a current worry or a positive personally relevant topic. High (but not low) worriers showed more evidence of restricted capacity during worry than when thinking about a positive topic. These findings suggest that high worriers have less residual working memory capacity when worrying than when thinking about other topics and, thus, have fewer attentional resources available to redirect their thoughts away from worry.     

Effect of working memory training on working memory,arithmetic and following instructions

Mathematical ability is dependent on specific mathematical training but also associated with a range of cognitive factors, including working memory (WM) capacity. Previous studies have shown that WM training leads to improvement in non-trained WM tasks, but the results regarding transfer to mathematics are inconclusive. In the present study, 176 children with WM deficits, aged 7–15 years performed 5 weeks of WM training. During the training period, they were assessed five times with a test of complex WM (the Odd One Out), a test of remembering and following instructions and a test of arithmetic. The improvements were compared to the performance of a control group of 304 typically developing children aged 7–15 years who performed the same transfer tasks at the same time intervals, but without training. The training group improved significantly more than the control group on all three transfer tests (all p < 0.0001), after correction for baseline performance, age and sex. The effect size for mathematics was small and the effect sizes for the WM tasks were moderate to large. The transfer increased linearly with the amount of training time and correlated with the amount of improvement on the trained tasks. These results confirm previous findings of training-induced improvements in non-trained WM tasks including the ability to follow instructions, but extend previous findings by showing improvements also for arithmetic. This is encouraging regarding the potential role of cognitive training for education, but it is desirable to find paradigms that would enhance the effect of the training on mathematics. One of the future challenges for studying training effects is combining large sample sizes with high quality and compliance, to detect relevant but smaller effects of cognitive training.     

The nature of individual differences in working memory capacity: active maintenance in primary memory and controlled search from secondary memory

Studies examining individual differences in working memory capacity have suggested that individuals with low working memory capacities demonstrate impaired performance on a variety of attention and memory tasks compared with individuals with high working memory capacities. This working memory limitation can be conceived of as arising from 2 components: a dynamic attention component (primary memory) and a probabilistic cue-dependent search component (secondary memory). This framework is used to examine previous individual differences studies of working memory capacity, and new evidence is examined on the basis of predictions of the framework to performance on immediate free recall. It is suggested that individual differences in working memory capacity are partially due to the ability to maintain information accessible in primary memory and the ability to search for information from secondary memory.     

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.     

Working memory deficits can be overcome: Impacts of training and medication on working memory in children with ADHD

This study evaluated the impact of two interventions—a training program and stimulant medication—on working memory (WM) function in children with attention deficit hyperactivity disorder (ADHD). Twenty‐five children aged between 8 and 11 years participated in training that taxed WM skills to the limit for a minimum of 20 days, and completed other assessments of WM and IQ before and after training, and with and without prescribed drug treatment. While medication significantly improved visuo‐spatial memory performance, training led to substantial gains in all components of WM across untrained tasks. Training gains associated with the central executive persisted over a 6‐month period. IQ scores were unaffected by either intervention. These findings indicate that the WM impairments in children with ADHD can be differentially ameliorated by training and by stimulant medication. Copyright © 2009 John Wiley & Sons, Ltd.     

Misleading postevent information and working memory capacity: an individual differences approach to eyewitness memory

The present study examines how individual differences in working memory capacity relate to the effect of misleading postevent information on memory for the original event. Participants were shown a film of a crime event and were then asked to unscramble a narrative that included misinformation regarding some of the film's details. Additionally, the working memory capacity of the participants was measured using the operation‐word span task. Finally, in a free recall test, participants recalled fewer correct details in the misinformation condition compared to the control condition. This effect was negatively correlated with working memory capacity. Copyright © 2002 John Wiley & Sons, Ltd.     

Trait anxiety, working memory capacity, and the effectiveness of memory suppression

We aimed at replicating the finding that humans are able to suppress unwanted memories, and tested whether this ability varies with individual differences in working memory capacity, trait anxiety and defensiveness. In a think/no-think experiment, participants either recalled or suppressed previously learned words for 0, 8 or 16 times. Suppression did not have an overall detrimental effect on later recall performance. However, higher recall rates after repeated suppression were exclusively predicted by higher trait anxiety. These results are discussed in relation to current theories on anxiety and executive control.     

Knowledge cannot explain the developmental growth of working memory capacity

According to some views of cognitive growth, the development of working memory capacity can account for increases in the complexity of cognition. It has been difficult to ascertain, though, that there actually is developmental growth in capacity that cannot be attributed to other developing factors. Here we assess the role of item familiarity. We document developmental increases in working memory for visual arrays of English letters versus unfamiliar characters. Although letter knowledge played a special role in development between the ages of 6 and 8 years, children with adequate letter knowledge showed practically the same developmental growth in normalized functions for letters and unfamiliar characters. The results contribute to a growing body of evidence that the developmental improvement in working memory does not wholly stem from supporting processes such as encoding, mnemonic strategies, and knowledge. A video abstract is available at: https://www.youtube.com/watch?v=LJdqErLR2Hs&feature=youtu.be     

Recall initiation strategies must be controlled in training studies that use immediate free recall tasks to measure the components of working memory capacity across time

There has been great interest in using working memory (WM) training regimens as an alternative treatment for ADHD, but it has recently been concluded that existing training regimens may not be optimally designed because they target the primary memory component but not the secondary component of WM capacity. This conclusion requires the ability to accurately measure changes in primary and secondary memory abilities over time. The immediate free recall task has been used in previous studies to measure these changes; however, one concern with these tasks is that the recall order required on training exercises may influence the recall strategy used during free recall, which may in turn influence the relative number of items recalled from primary and secondary memory. To address this issue, previous training studies have explicitly controlled recall strategy before and after training. However, the necessity of controlling for recall strategies has not been explicitly tested. The present study investigated the effects of forward-serial-order training on free recall performance under conditions in which recall strategy was not controlled using a sample of adolescents with ADHD. Unlike when recall order was controlled, the main findings showed selective improvement of the secondary memory component (as opposed to the primary memory component) when recall order was uncontrolled. This finding advances our understanding of WM training by highlighting the importance of controlling for recall strategies when free recall tasks are used to measure changes in the primary and secondary components of WM across time.     

Neural effects of short-term training on working memory

Working memory training has been the focus of intense research interest. Despite accumulating behavioral work, knowledge about the neural mechanisms underlying training effects is scarce. Here, we show that 7 days of training on an n-back task led to substantial performance improvements in the trained task; furthermore, the experimental group showed cross-modal transfer, as compared with an active control group. In addition, there were two neural effects that emerged as a function of training: first, increased perfusion during task performance in selected regions, reflecting a neural response to cope with high task demand; second, increased blood flow at rest in regions where training effects were apparent. We also found that perfusion at rest was correlated with task proficiency, probably reflecting an improved neural readiness to perform. Our findings are discussed within the context of the available neuroimaging literature on n-back training.     

The reliability and stability of visual working memory capacity

Because of the central role of working memory capacity in cognition, many studies have used short measures of working memory capacity to examine its relationship to other domains. Here, we measured the reliability and stability of visual working memory capacity, measured using a single-probe change detection task. In Experiment 1, the participants (N = 135) completed a large number of trials of a change detection task (540 in total, 180 each of set sizes 4, 6, and 8). With large numbers of both trials and participants, reliability estimates were high (α > .9). We then used an iterative down-sampling procedure to create a look-up table for expected reliability in experiments with small sample sizes. In Experiment 2, the participants (N = 79) completed 31 sessions of single-probe change detection. The first 30 sessions took place over 30 consecutive days, and the last session took place 30 days later. This unprecedented number of sessions allowed us to examine the effects of practice on stability and internal reliability. Even after much practice, individual differences were stable over time (average between-session r = .76).     

The effect of working memory capacity on conflict monitoring

The conflict adaptation effect, a reduced interference effect upon the detection of a conflict signal (e.g., following an incongruent trial), has been interpreted as evidence for active regulation of top-down cognitive control. We hypothesized that the extent of conflict adaptation should be related to individuals' working memory capacity (WMC), which has been repeatedly demonstrated to reflect the level of cognitive control. Using the Simon task, in Experiment 1, we quantified the conflict adaptation ratio (CAR) transiently as the ratio of the conflict effect following an incongruent trial to the conflict effect following a congruent trial, controlling for the reaction time that often correlates with WMC. We observed that the CAR varied from highly negative with low WMC scores to near-zero with high WMC scores. This result suggests that high WMC individuals, when detecting conflict, adjust the level of cognitive control optimally so that their performance is less susceptible to the presence of a distractor. In Experiment 2, we quantified the CAR in a sustained manner as the ratio of the conflict effect from predominantly incongruent blocks to the conflict effect from predominantly congruent blocks. Again, the CAR varied from negative to zero as WMC increased. These results suggest that WMC may reflect, in addition to the ability to maintain a level of control, the ability to adjust the level of control appropriately to the contextual demands.     

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.     

Self-rated autistic-like traits and capacity of visual working memory

The effect on the capacity of visual working memory of spatial complexity (as defined by Garner's principle) in rotation and reflection transformation was examined in persons differing along the Autism Spectrum Quotient (AQ), using a change-detection task. On each trial, nine line segments were arrayed in simple, medium, and complex configurations, which were presented in memory and test displays. 27 participants (8 men, 19 women; M age = 22.3 yr., SD = 2.7) were asked whether the orientations of stimuli between two displays were the same or different. On the basis of their AQ scores out of 50 (M AQ scores = 20.9, SD = 6.3), the participants were divided into groups with high (n = 13; M AQ scores = 26.2, SD = 4.1) and low (n = 12; M AQ scores = 15.3, SD = 2.7) self-reported autistic-like traits (High and Low AQ groups, 2 excluded for scores at the median). The results showed that spatial complexity affects the capacity of visual working memory for the Low AQ group but not for the High AQ group, suggesting the functional dissociation of spatial configuration and visual working memory in the High AQ group.     

Motion tracking modulates capacity allocation of visual working memory

Previous studies on visual working memory (VWM) have primarily investigated memory for an array presented for a single moment. Here, we examined VWM for two arrays separated by a 1,100-msec interval. We focused on the allocation of VWM capacity to the two arrays as a function of dynamic events inserted between them. During the interval, irrelevant dots moved to form three types of motion: (1) coherent (apparent) motion that connected Arrays 1 and 2, (2) jumpy motion, or (3) coherent motion with two disconnected segments. Results showed that VWM for Array 2’s locations was better than for Array 1’s, especially when the arrays were connected by coherent motion. We suggest that coherent motion between two temporally disparate arrays connects the arrays into a single visual event VWM is then biased toward remembering the more recent state of the event.