Working memory training remains a work in progress

Can we enhance working memory? Bias and effectiveness in cognitive training studies

Meta-analyses have found that working memory (WM) can be improved with cognitive training; however, some authors have suggested that these improvements are mostly driven by biases in the measurement of WM, especially the use of similar tasks for assessment and training. In the present meta-analysis, we investigated whether WM, fluid intelligence, executive functions, and short-term memory can be improved by cognitive training and evaluated the impact of possible sources of bias. We performed a risk of bias assessment of the included studies and took special care in controlling for practice effects. Data from 52 independent comparisons were analyzed, including cognitive training aimed at different cognitive functions. Our results show small improvements in WM after training (SMD = 0.18). Much larger effects were observed when the analysis was restricted to assessment tasks similar to those used for training (SMD = 1.15). Fluid intelligence was not found to improve as a result of training, and improvements in WM were not related to changes in fluid intelligence. Our analyses did however indicate that cognitive training can improve specific executive functions. Contrary to expectations, a set of meta-regressions indicated that characteristics of the training programme, such as dosage and type of training, do not have an impact on the effectiveness of training. The risk of bias assessment revealed some concerns in the randomization process and possible selective reporting among studies. Overall, our results identified various potential sources of bias, with the most significant being the choice of assessment tasks.

A classroom intervention targeting working memory, attention and language skills: a cluster randomised feasibility trial

Background

International debate around the best models of speech and language therapy provision for children with language disorders has highlighted the need for research into classroom-based approaches and intervention dosage. Working memory (WM) is a cognitive skill linked to attention and language. ‘Recall to Enhance Children’s Attention, Language and Learning’ (RECALL) is a novel, 6-week, classroom-based intervention delivered by health professionals (HPs) and teachers. It is designed to target WM and enhance attention and language skills in 4–5 year olds.

Methods

A cluster randomised feasibility trial was conducted to investigate aspects of the feasibility of a definitive trial to evaluate RECALL: (i) recruitment and sampling procedures; (ii) compliance and fidelity; (iii) the acceptability of RECALL to HPs and teachers; (iv) the appropriateness of the outcome measures. Six classes of 4–5 year olds participated: two received RECALL, two received an existing intervention targeting attention skills (not underpinned by WM theory), and two received education as usual (no intervention). Ten children in each class (n = 60) were sampled to assess the appropriateness of the outcome measures. Classroom observations were conducted to measure fidelity and semi-structured interviews with HPs, and teachers explored the acceptability of RECALL.

Results

The recruitment targets were met, and all six schools completed the trial, but the sampling procedures require modification. Compliance was good (95% of RECALL sessions were delivered), but fidelity to the intervention protocol varied between 76% and 45% across the two schools. This was influenced by large class sizes, child factors, and facilitator factors, e.g., their understanding of the theory underpinning the intervention. The lack of fidelity reduced the dose (number of practice items) accessed by individual children, particularly those most at risk. There were mixed findings regarding the acceptability of RECALL and the appropriateness of the outcome measures.

Conclusions

The trial protocol could be easily scaled-up in a future definitive trial, with an amended sampling procedure. RECALL should be repackaged as a small group intervention to enhance the fidelity of its delivery and its acceptability to HPs and teachers. This study highlights the need for thorough training for professionals who deliver classroom-based interventions for children with language disorders.

Trial registration

ISRCTN13633886. Registered on 7 September 2018

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-021-00771-w.

A classroom-based intervention targeting working memory, attention and language skills in 4-5 year olds (RECALL): study protocol for a cluster randomised feasibility trial

BACKGROUND

There is international recognition of the need for creative, classroom-based interventions to support children at risk of low academic achievement and well-being, due to poor attention and language skills on school entry. Working memory (WM) is a cognitive skill that is strongly associated with attention and language skills. There has been speculation that WM training, embedded within typical educational activities, may improve children's WM skills and produce transfer effects to real-world skills such as attention and language. However, little is known about the effectiveness of this approach.'Recall to Enhance Children's Attention, Language and Learning' (RECALL) is a novel, 6-week, classroom-based intervention targeting WM, attention and language skills in 4-5 year olds. RECALL was co-produced with health professionals, teachers and parents. This protocol describes the rationale, methods and analysis plan for a proposed cluster randomised feasibility trial of this RECALL programme.

METHODS

This is a three-arm, cluster randomised feasibility trial comparing RECALL to an existing programme (active control), and no-intervention (education as usual). We will recruit six schools in socially disadvantaged areas in one region of the UK. Two schools will be randomly allocated to each arm of the trial. In each school, one class of children (ages 4-5 years) of approx. 30 children will be involved in this study. Ten children in each class will be sampled purposefully for outcome measurement including: standardised assessments of WM, language and attention skills; teacher ratings of attention; and parent ratings of functional communication skills. These will be administered at baseline and 1-week post-intervention in order to test the acceptability of the measures. A process evaluation using semi-structured interviews with participants will explore the acceptability of RECALL and the procedures employed in this trial.

DISCUSSION

This feasibility study will explore the acceptability of RECALL to the health professionals and teachers who will deliver it and inform the optimal design of the programme. The inclusion of an active control group and the blinding of outcomes assessors enhance rigour in this study. The findings will determine whether this study can be scaled-up into a definitive cluster randomised trial to evaluate the effectiveness of RECALL.

TRIAL REGISTRATION

ISRCTN13633886. Registered 7 Sept 2018.

Interventions targeting working memory in 4-11 year olds within their everyday contexts: A systematic review

It has been suggested that diverse interventions applied within children's everyday contexts have the potential to improve working memory (WM) and produce transfer to real-world skills but little is known about the effectiveness of these approaches. This review aims to examine systematically the effectiveness of non-computerised interventions with 4-11 year olds to identify: (i) their effects on WM; (ii) whether benefits extend to near- and far-transfer measures; (iii) if gains are sustained over time; (iv) the active ingredients; and (v) the optimum dosage. Searches were conducted across 12 electronic databases using consistent keywords. Papers were screened by title and abstract (n = 6212) and judged against pre-defined eligibility criteria (n = 63). Eighteen papers were included in the review. They used a range of non-computerised WM intervention approaches that included: (i) adapting the environment to reduce WM loads; (ii) direct WM training with and without strategy instruction; and (iii) training skills which may indirectly impact on WM (physical activity, phonological awareness, fantastical play and inhibition). Both direct training on WM tasks and practicing certain skills that may impact indirectly on WM (physical activity, fantastical play and inhibition) produced improvements on WM tasks, with some benefits for near-transfer activities. The common ingredient across effective interventions was the executive-loaded nature of the trained task i.e., training on a task that taps into attentional and processing resources under executive control and not just the storage of information. Few studies reported dosage effects, measured far-transfer effects (n = 4), or tested the durability of gains over time (n = 4). The lack of a clear theoretical framework in many of the included studies resulted in ambiguous predictions about training and transfer effects, and inadequate use of outcome measures. Methodological issues also constrain the strength of the evidence, including: small samples sizes; an absence of blinding of participant and outcome assessors; and lack of active control groups. Further well-designed and controlled studies with clear theoretical underpinnings are required to expand and enhance the evidence base. The heterogeneity of the interventions and of the study designs (randomised and non-randomised) in the included papers limited the synthesis of evidence across studies. However, this diversity enabled the identification of key ingredients, notably the training of executive-loaded WM tasks, which can help inform novel approaches to WM intervention in everyday contexts.

Training Working Memory of Children with and without Dyslexia

For the future school performance of a child in the fields of literacy and numeracy, the operational efficiency of working memory is a central predictor. Children affected by dyslexia exhibit specific deficits in the functions of working memory. A software application for elementary school-age children has been specifically developed for this study, attempting to improve the working memory's operational efficiency. Based on Baddeley's model of working memory (1986), the phonological loop, the visuo-spatial sketchpad, and the central executive were trained in 18 sessions over a period of six weeks. The group of test subjects undergoing this training was composed of third-graders, of which 43 were and 27 were not affected by dyslexia. The untrained control group was made up of 41 third-graders with dyslexia and 28 without dyslexia. While the short-term effects of the program could not be proven, the present analyses focus on long-term effects. The results obtained from a pre-test/follow-up design reveal that no long-term increases in performance regarding phonological and central executive working memory could be confirmed. Only the visuo-spatial Corsi block span exhibited a training effect over a period of three months. Additionally, training did not show any long-term effect of performance improvement, not even for a subgroup of children with dyslexia and an especially low working memory performance. Thus, even after this study, the question whether working memory can be trained or not remains partly unanswered but leaves us predominantly pessimistic.

How to play 20 questions with nature and lose: Reflections on 100 years of brain-training research

Despite dozens of empirical studies and a growing body of meta-analytic work, there is little consensus regarding the efficacy of cognitive training. In this review, we examine why this substantial corpus has failed to answer the often-asked question, "Does cognitive training work?" We first define cognitive training and discuss the general principles underlying training interventions. Next, we review historical interventions and discuss how findings from this early work remain highly relevant for current cognitive-training research. We highlight a variety of issues preventing real progress in understanding the underlying mechanisms of training, including the lack of a coherent theoretical framework to guide training research and methodological issues across studies and meta-analyses. Finally, suggestions for correcting these issues are offered in the hope that we might make greater progress in the next 100 y of cognitive-training research.

Working memory training revisited: A multi-level meta-analysis of n-back training studies

The efficacy of working memory (WM) training has been a controversial and hotly debated issue during the past years. Despite a large number of training studies and several meta-analyses, the matter has not yet been solved. We conducted a multi-level meta-analysis on the cognitive transfer effects in healthy adults who have been administered WM updating training with n-back tasks, the most common experimental WM training paradigm. Thanks to this methodological approach that has not been employed in previous meta-analyses in this field, we were able to include effect sizes from all relevant tasks used in the original studies. Altogether 203 effect sizes were derived from 33 published, randomized, controlled trials. In contrast to earlier meta-analyses, we separated task-specific transfer (here untrained n-back tasks) from other WM transfer tasks. Two additional cognitive domains of transfer that we analyzed consisted of fluid intelligence (Gf) and cognitive control tasks. A medium-sized transfer effect was observed to untrained n-back tasks. For other WM tasks, Gf, and cognitive control, the effect sizes were of similar size and very small. Moderator analyses showed no effects of age, training dose, training type (single vs. dual), or WM and Gf transfer task contents (verbal vs. visuospatial). We conclude that a substantial part of transfer following WM training with the n-back task is task-specific and discuss the implications of the results to WM training research.

Are training and transfer effects of working memory updating training modulated by achievement motivation?

Previous studies examining effects of working memory (WM) updating training revealed mixed results. One factor that might modulate training gains, and possibly also transfer of those gains to non-trained cognitive tasks, is achievement motivation. In the present Studies 1 and 2, students with either a high (HAM) or low (LAM) achievement motivation completed a 14-day visuospatial WM updating training program. In Study 2, the students also performed a set of tasks measuring other executive functions and fluid intelligence prior to and after training. In both studies, the HAM students displayed a larger training gain than the LAM students. Study 2 revealed that after training, both groups showed better performance on the near-transfer but not far-transfer tasks. Importantly, the differential training gain was not associated with better post-training performance for the HAM compared to the LAM students on any of the transfer tasks. These results are taken to support a modulatory role of achievement motivation on WM training benefits, but not on transfer of those benefits to other tasks. Possible reasons for the general improvement on the near-transfer tasks and the absence of a modulatory role of achievement motivation on transfer-task performance are discussed.

Working Memory Capacity and Fluid Intelligence: Maintenance and Disengagement

Working memory capacity and fluid intelligence have been demonstrated to be strongly correlated traits. Typically, high working memory capacity is believed to facilitate reasoning through accurate maintenance of relevant information. In this article, we present a proposal reframing this issue, such that tests of working memory capacity and fluid intelligence are seen as measuring complementary processes that facilitate complex cognition. Respectively, these are the ability to maintain access to critical information and the ability to disengage from or block outdated information. In the realm of problem solving, high working memory capacity allows a person to represent and maintain a problem accurately and stably, so that hypothesis testing can be conducted. However, as hypotheses are disproven or become untenable, disengaging from outdated problem solving attempts becomes important so that new hypotheses can be generated and tested. From this perspective, the strong correlation between working memory capacity and fluid intelligence is due not to one ability having a causal influence on the other but to separate attention-demanding mental functions that can be contrary to one another but are organized around top-down processing goals.

Effects of working memory training on children born preterm

Researchers have reported benefits of working memory training in various populations, however, the training gains in preterm population is still inadequately studied. This study aimed to investigate the transfer and lasting effects of an online working memory training program on a group of preterm children aged between 4 and 6 years (mean gestational age = 28.3 weeks; mean birth weight = 1153 grams). Children were asked to perform the Cogmed JM at home for approximately 15 minutes a day, 5 days a week for 5 weeks. Their nontrained working memory and attention were assessed pre-training, post-training, and at 5-week follow-up. Parent ratings on children's executive functions were obtained at the three time points. Results revealed that significant improvements in verbal working memory was emerging in preterm children at 5-week follow-up, while significant gains in visuospatial working memory was found post-training and at 5-week follow-up in age-matched term-born children. These results indicated that working memory training has benefits on preterm children; however, the gains are different from those observed in term-born children. No significant differences in attention and parent-rated EF were found in either group across time. The possible explanations for the training benefits observed in preterm children were discussed.

Different developmental trajectories across feature types support a dynamic field model of visual working memory development

Research on visual working memory has focused on characterizing the nature of capacity limits as "slots" or "resources" based almost exclusively on adults' performance with little consideration for developmental change. Here we argue that understanding how visual working memory develops can shed new light onto the nature of representations. We present an alternative model, the Dynamic Field Theory (DFT), which can capture effects that have been previously attributed either to "slot" or "resource" explanations. The DFT includes a specific developmental mechanism to account for improvements in both resolution and capacity of visual working memory throughout childhood. Here we show how development in the DFT can account for different capacity estimates across feature types (i.e., color and shape). The current paper tests this account by comparing children's (3, 5, and 7 years of age) performance across different feature types. Results showed that capacity for colors increased faster over development than capacity for shapes. A second experiment confirmed this difference across feature types within subjects, but also showed that the difference can be attenuated by testing memory for less familiar colors. Model simulations demonstrate how developmental changes in connectivity within the model-purportedly arising through experience-can capture differences across feature types.

Combined cognitive and parent training interventions for adolescents with ADHD and their mothers: A randomized controlled trial

This study examined the individual and combined effects of two nonpharmacological treatments for attention deficit/hyperactivity disorder (ADHD): Cogmed working memory training (CWMT) for adolescents and behavioral parent training (BPT) for mothers. Ninety-one adolescents (ages 11-15) and their mothers were randomized to one of four CWMT and BPT treatment and active control (placebo) group combinations of 5-week interventions. At pre- and posttest, mothers and teachers completed rating forms, and adolescents completed neuropsychological measures of working memory (WM). Individual intervention effects showed that treatment CWMT significantly improved WM spans, whereas there were no significant differences for treatment or control BPT on reports of parent-related outcomes. Combined treatment effects indicated an overall pattern of greatest improvements for the control CWMT/treatment BPT group, as compared to the other three groups, on adolescent WM deficit, behavioral regulation problems, and global executive deficit. Most significant effects for outcomes were main effects of improvements over time. A combination of CWMT and BPT did not result in increased treatment gains. However, potential effects of combined treatment may have been masked by greater perceived benefits arising from lack of struggle in the nonadaptive, CWMT active control condition. Future combined intervention research should focus on specific, theoretically driven WM deficits among individuals with ADHD, should include possible adaptations to the standard CWMT program, should examine effectiveness of cognitive treatments combined with contextual interventions and should utilize appropriate control groups to fully understand the unique and combined effects of interventions.