Is working memory capacity fixed?

Working memory capacity predicts focus back effort under different task demands

According to the cognitive flexibility view, individuals with higher cognitive control ability are more flexible in experiencing on task or mind wandering during tasks with different loads. On the other hand, the resource-control theory posits that executive control is essential for allocating attentional resources between mind wandering and tasks. Focus back effort may reflect the adjustment of executive control in the resource-control theory. Here, 121 participants completed two span tasks, as well as high- and low-load tasks, while mind wandering and focus back effort were measured. Our findings indicated that mind wandering was influenced by working memory capacity (WMC) and focus back effort. Additionally, participants demonstrated a higher focus back effort during the higher load task. This effect was particularly pronounced in individuals with lower WMC, which was treated as a continuous variable. These findings integrate the cognitive flexibility view and resource-control theory to describe how individuals modulate mind wandering.

Teacher perceptions of working memory and executive function improvements following school-day cognitive training

Considerable research has documented the impact of teacher perceptions on students’ academic-related outcomes (e.g., classroom performance). This body of literature clearly shows that teacher perceptions (resulting from direct interactions with students) can have both positive and negative effects with respect to student behaviors and experiences in the classroom. What remains unclear is whether teachers perceive changes that result from interventions administered outside of their classrooms. The purpose of this study was to examine changes in teacher perceptions of working memory and executive function concerns (two important predictors of academic success) among students who participated in a computerized cognitive training program designed to enhance working memory skills. The current results indicate that teachers perceived fewer concerns following students’ participation in the training; this outcome was supplemented with significant improvements in the students’ working memory capabilities following the training program. These findings have important implications given the literature highlighting the relation between teacher perceptions and student outcomes as a function of a school-based computerized cognitive training intervention.

What Is Targeted When We Train Working Memory? Evidence From a Meta-Analysis of the Neural Correlates of Working Memory Training Using Activation Likelihood Estimation

Working memory (WM) is the system responsible for maintaining and manipulating information, in the face of ongoing distraction. In turn, WM span is perceived to be an individual-differences construct reflecting the limited capacity of this system. Recently, however, there has been some evidence to suggest that WM capacity can increase through training, raising the possibility that training can functionally alter the neural structures supporting WM. To address the hypothesis that the neural substrates underlying WM are targeted by training, we conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of WM training using Activation Likelihood Estimation (ALE). Our results demonstrate that WM training is associated exclusively with decreases in blood oxygenation level-dependent (BOLD) responses in clusters within the fronto-parietal system that underlie WM, including the bilateral inferior parietal lobule (BA 39/40), middle (BA 9) and superior (BA 6) frontal gyri, and medial frontal gyrus bordering on the cingulate gyrus (BA 8/32). We discuss the various psychological and physiological mechanisms that could be responsible for the observed reductions in the BOLD signal in relation to WM training, and consider their implications for the construct of WM span as a limited resource.

Transfer Effects of Working Memory Intervention on Linguistic Abilities in Patients with Dementia

Purpose: Working memory training for Alzheimer’s disease (AD) patients may yield everyday cognitive- linguistic benefits by facilitating transfer effects in multiple domains. The purpose of this study was to investigate the effects of working memory intervention and differences on transfer effects in type of intervention paradigm like core training (CT) and strategy training (ST).Methods: A total of 24 patients with mild and moderate AD were divided into CT and ST group (n = 12, respectively). After CT and ST interventions, we assessed their transfer effects on linguistic abilities including reading comprehension, figurative language, word fluency, and discourse production. Results: There were three main findings. Firstly, CT group improved significantly in figurative language, word fluency, and discourse production. Secondly, ST group showed the significant intervention gains in figurative language and discourse production. Thirdly, CT group had higher transfer effects in figurative language and discourse production than ST group, while both were similar in other transfer effects.Conclusion: This study proves that effects of working memory intervention for AD patients are different in type of paradigm, and thereby presents a roadmap for increasing the efficacy and utilization of working memory intervention in clinical settings.

Fluid intelligence is related to capacity in memory as well as attention: Evidence from middle childhood and adulthood

Human fluid intelligence emerges from the interactions of various cognitive processes. Although some classic models characterize intelligence as a unitary "general ability," many distinct lines of research have suggested that it is possible to at least partially decompose intelligence into a set of subsidiary cognitive functions. Much of this work has focused on the relationship between intelligence and working memory, and more specifically between intelligence and the capacity-loading aspects of working memory. These theories focus on domain-general processing capacity limitations, rather than limitations specifically linked to working memory tasks. Performance on other capacity-constrained tasks, even those that have typically been given the label of "attention tasks," may thus also be related to fluid intelligence. We tested a wide range of attention and working memory tasks in 7- to 9-year-old children and adults, and we used the results of these cognitive measures to predict intelligence scores. In a set of 13 measures we did not observe a single "positive manifold" that would indicate a general-ability understanding of intelligence. Instead, we found that a small number of measures were related to intelligence scores. More specifically, we found two tasks that are typically labeled as "attentional measures", Multiple Object Tracking and Enumeration, and two tasks that are typically labeled as "working memory" measures, N-back and Spatial Span, were reliably related to intelligence. However, the links between attention and intelligence scores were fully mediated by working memory measures. In contrast, attention scores did not mediate the relations between working memory and intelligence. Furthermore, these patterns were indistinguishable across age groups, indicating a hierarchical cognitive basis of intelligence that is stable from childhood into adulthood.

Divergent Research Methods Limit Understanding of Working Memory Training

Working memory training has been a hot topic over the last decade. Although studies show benefits in trained and untrained tasks as a function of training, there is an ongoing debate on the efficacy of working memory training. There have been numerous meta-analyses put forth to the field, some finding overall broad transfer effects while others do not. However, discussion of this research typically overlooks specific qualities of the training and transfer tasks. As such, there has been next to no discussion in the literature on what training and transfer tasks features are likely to mediate training outcomes. To address this gap, here, we characterized the broad diversity of features employed in N-back training tasks and outcome measures in published working memory training studies. Extant meta-analyses have not taken into account the diversity of methodology at this level, primarily because there are too few studies using common methods to allow for a robust meta-analysis. We suggest that these limitations preclude strong conclusions from published data. In order to advance research on working memory training, and in particular, N-back training, more studies are needed that systematically compare training features and use common outcome measures to assess transfer effects.

A randomized controlled trial of the effects of working memory training in methadone maintenance patients

OBJECTIVE

Working memory impairment in individuals with chronic opioid dependence can play a major role in cognitive and treatment outcomes. Cognitive training targeting working memory shows promise for improved function in substance use disorders. To date, cognitive training has not been incorporated as an adjunctive treatment for opioid dependence.

METHODS

Methadone maintenance patients were randomly assigned to experimental (n=28) or active control (n=28) 25-session computerized training and run in parallel. Cognitive and drug use outcomes were assessed before and after training.

RESULTS

Participants in the experimental condition showed performance improvements on two of four working memory measures, and both groups improved on a third measure of working memory performance. Less frequent drug use was found in the experimental group than in the control group post-training. In contrast to previous findings with stimulant users, no significant effect of working memory training on delay discounting was found using either hypothetical or real rewards. There were no group differences on working memory outcome measures that were dissimilar from the training tasks, suggesting that another mechanism (e.g., increased distress tolerance) may have driven drug use results.

CONCLUSIONS

Working memory training improves performance on some measures of working memory in methadone maintenance patients, and may impact drug use outcomes. Working memory training shows promise in patients with substance use disorders; however, further research is needed to understand the mechanisms through which performance is improved and drug use outcomes are impacted.

Transfer after Working Memory Updating Training

During the past decade, working memory training has attracted much interest. However, the training outcomes have varied between studies and methodological problems have hampered the interpretation of results. The current study examined transfer after working memory updating training by employing an extensive battery of pre-post cognitive measures with a focus on near transfer. Thirty-one healthy Finnish young adults were randomized into either a working memory training group or an active control group. The working memory training group practiced with three working memory tasks, while the control group trained with three commercial computer games with a low working memory load. The participants trained thrice a week for five weeks, with one training session lasting about 45 minutes. Compared to the control group, the working memory training group showed strongest transfer to an n-back task, followed by working memory updating, which in turn was followed by active working memory capacity. Our results support the view that working memory training produces near transfer effects, and that the degree of transfer depends on the cognitive overlap between the training and transfer measures.

Working Memory Training in Post-Secondary Students with ADHD: A Randomized Controlled Study

OBJECTIVES

To determine whether standard-length computerized training enhances working memory (WM), transfers to other cognitive domains and shows sustained effects, when controlling for motivation, engagement, and expectancy.

METHODS

97 post-secondary students (59.8% female) aged 18-35 years with Attention-Deficit/Hyperactivity Disorder, were randomized into standard-length adaptive Cogmed WM training (CWMT; 45-min/session), a shortened-length adaptive version of CWMT (15 min/session) that controlled for motivation, engagement and expectancy of change, or into a no training group (waitlist-control group). All three groups received weekly telephone calls from trained coaches, who supervised the CWMT and were independent from the research team. All were evaluated before and 3 weeks post-training; those in the two CWMT groups were also assessed 3 months post-training. Untrained outcome measures of WM included the WAIS-IV Digit Span (auditory-verbal WM), CANTAB Spatial Span (visual-spatial WM) and WRAML Finger Windows (visual-spatial WM). Transfer-of-training effects included measures of short-term memory, cognitive speed, math and reading fluency, complex reasoning, and ADHD symptoms.

RESULTS

Performance on 5/7 criterion measures indicated that shortened-length CWMT conferred as much benefit on WM performance as did standard-length training, with both CWMT groups improving more than the waitlist-control group. Only 2 of these findings remained robust after correcting for multiple comparisons. Follow-up analyses revealed that post-training improvements on WM performance were maintained for at least three months. There was no evidence of any transfer effects but the standard-length group showed improvement in task-specific strategy use.

CONCLUSIONS

This study failed to find robust evidence of benefits of standard-length CWMT for improving WM in college students with ADHD and the overall pattern of findings raise questions about the specificity of training effects.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01657721.

Effects and mechanisms of working memory training: a review

Can cognitive abilities such as reasoning be improved through working memory training? This question is still highly controversial, with prior studies providing contradictory findings. The lack of theory-driven, systematic approaches and (occasionally serious) methodological shortcomings complicates this debate even more. This review suggests two general mechanisms mediating transfer effects that are (or are not) observed after working memory training: enhanced working memory capacity, enabling people to hold more items in working memory than before training, or enhanced efficiency using the working memory capacity available (e.g., using chunking strategies to remember more items correctly). We then highlight multiple factors that could influence these mechanisms of transfer and thus the success of training interventions. These factors include (1) the nature of the training regime (i.e., intensity, duration, and adaptivity of the training tasks) and, with it, the magnitude of improvements during training, and (2) individual differences in age, cognitive abilities, biological factors, and motivational and personality factors. Finally, we summarize the findings revealed by existing training studies for each of these factors, and thereby present a roadmap for accumulating further empirical evidence regarding the efficacy of working memory training in a systematic way.

Few effects of far transfer of working memory training in ADHD: a randomized controlled trial

Objective

Studies have shown that children with ADHD profit from working memory training, although few studies have investigated transfer effects comprehensively. The current Randomized Controlled Trial analyzes transfer to other neuropsychological (NP) domains, academic performance and everyday functioning at home and school.

Method

Sixty-seven children with ADHD were randomized into a control group or a training group. The training group underwent Cogmed’s RoboMemo program. All participants were assessed pre-training, immediately after and eight months later with a battery of NP tests, measures of mathematical and reading skills, as well as rating scales filled out by parents and teachers.

Results

There was a significant training effect in psychomotor speed, but not to any other NP measures. Reading and mathematics were improved. There were no training induced changes in symptom rating scales either at home or at school. The increased reading scores remained significant eight months later.

Conclusion

The study is the most comprehensive study of transfer effects to date, and with mixed results compared to previous research. More research is needed regarding how to improve the training program and the conditions and thresholds for successful training.

Trial Registration

Controlled-Trials.com ISRCTN19133620

Does working memory training lead to generalized improvements in children with low working memory? A randomized controlled trial

Children with low working memory typically make poor educational progress, and it has been speculated that difficulties in meeting the heavy working memory demands of the classroom may be a contributory factor. Intensive working memory training has been shown to boost performance on untrained memory tasks in a variety of populations. This first randomized controlled trial with low working memory children investigated whether the benefits of training extend beyond standard working memory tasks to other more complex activities typical of the classroom in which working memory plays a role, as well as to other cognitive skills and developing academic abilities. Children aged 7–9 years received either adaptive working memory training, non-adaptive working memory training with low memory loads, or no training. Adaptive training was associated with selective improvements in multiple untrained tests of working memory, with no evidence of changes in classroom analogues of activities that tax working memory, or any other cognitive assessments. Gains in verbal working memory were sustained one year after training. Thus the benefits of working memory training delivered in this way may not extend beyond structured working memory tasks.