Increased training complexity reduces the effectiveness of brief working memory training: evidence from short-term single and dual n-back training interventions

N-back training has recently come under intense scientific scrutiny due to reports of training-related improvements in general fluid intelligence. As of yet, relatively little is known about the effects of short-term n-back training interventions, however. In a pretest-training-posttest design, we compared brief dual and single n-back training regimen in terms of training gains and transfer effects relative to a passive control group. Transfer effects indicated that, in the short-term, single n-back training may be the more effective training task: At the short training duration we employed, neither training group showed far transfer to specific task switch costs, Stroop inhibition costs or matrix reasoning indexing fluid intelligence. Yet, both types of training resulted in a reduction of general task switch costs indicating improved cognitive control during the sustained maintenance of competing task sets. Single but not dual n-back training additionally yielded near transfer to an untrained working memory updating task.     

The concurrent validity and test–retest reliability of a visuospatial working memory task

To determine whether the visuospatial n-back working memory task is a reliable and valid measure of cognitive processes believed to underlie intelligence, this study compared the reaction times and accuracy of performance of 70 participants, with performance on the Multidimensional Aptitude Battery (MAB). Testing was conducted over two sessions separated by 1 week. Participants completed the MAB during the second test session. Moderate test–retest reliability for percentage accuracy scores was found across the four levels of the n-back task, whilst reaction times were highly reliable. Furthermore, participants' performance on the MAB was negatively correlated with accuracy of performance at the easier levels of the n-back task and positively correlated with accuracy of performance at the harder task levels. These findings confirm previous research examining the cognitive basis of intelligence, and suggest that intelligence is the product of faster speed of information processing, as well as superior working memory capacity.     

Dual n-back training increases the capacity of the focus of attention

Working memory (WM) training has been reported to benefit abilities as diverse as fluid intelligence (Jaeggi et al., Proceedings of the National Academy of Sciences of the United States of America, 105:6829–6833, 2008) and reading comprehension (Chein & Morrison, Psychonomic Bulletin & Review, 17:193–199, 2010), but transfer is not always observed (for reviews, see Morrison & Chein, Psychonomics Bulletin & Review, 18:46–60, 2011; Shipstead et al., Psychological Bulletin, 138:628–654, 2012). In contrast, recent WM training studies have consistently reported improvement on the trained tasks. The basis for these training benefits has received little attention, however, and it is not known which WM components and/or processes are being improved. Therefore, the goal of the present study was to investigate five possible mechanisms underlying the effects of adaptive dual n-back training on working memory (i.e., improvements in executive attention, updating, and focus switching, as well as increases in the capacity of the focus of attention and short-term memory). In addition to a no-contact control group, the present study also included an active control group whose members received nonadaptive training on the same task. All three groups showed significant improvements on the n-back task from pretest to posttest, but adaptive training produced larger improvements than did nonadaptive training, which in turn produced larger improvements than simply retesting. Adaptive, but not nonadaptive, training also resulted in improvements on an untrained running span task that measured the capacity of the focus of attention. No other differential improvements were observed, suggesting that increases in the capacity of the focus of attention underlie the benefits of adaptive dual n-back training.     

Adaptive n-back training does not improve fluid intelligence at the construct level: Gains on individual tests suggest that training may enhance visuospatial processing

Short-term adaptive cognitive training based on the n-back task is reported to increase scores on individual ability tests, but the key question of whether such increases generalize to the intelligence construct is not clear. Here we evaluate fluid/abstract intelligence (Gf), crystallized/verbal intelligence (Gc), working memory capacity (WMC), and attention control (ATT) using diverse measures, with equivalent versions, for estimating any changes at the construct level after training. Beginning with a sample of 169 participants, two groups of twenty-eight women each were selected and matched for their general cognitive ability scores and demographic variables. Under strict supervision in the laboratory, the training group completed an intensive adaptive training program based on the n-back task (visual, auditory, and dual versions) across twenty-four sessions distributed over twelve weeks. Results showed that this group had the expected systematic improvements in n-back performance over time; this performance systematically correlated across sessions with Gf, Gc, and WMC, but not with ATT. However, the main finding showed no significant changes in the assessed psychological constructs for the training group as compared with the control group. Nevertheless, post-hoc analyses suggested that specific tests and tasks tapping visuospatial processing might be sensitive to training.     

工作记忆训练提升幼儿流体智力表现

目前已有许多研究证据表明, 工作记忆训练能提高成人、儿童的流体智力成绩, 然而这种训练是否能够提高幼儿的流体智力表现, 更为重要的是, 如果训练确有成效, 那么这种训练效果能否长期保持？为此, 本研究选择了幼儿园4~5岁幼儿进行工作记忆训练任务, 考察工作记忆训练对流体智力的提升及保持效应。实验中设立3个组：实验组、控制1组和控制2组。实验组采用单个空间n-back的工作记忆游戏程序进行训练, 控制1组采用“水果忍者”的游戏程序进行训练, 两组进行游戏训练的时间均为14天, 每天15 min; 控制2组不进行任何训练。结果发现, 训练后实验组幼儿被试的流体智力成绩明显优于两个控制组, 在6个月后再进行测试, 这种优势仍然保持。本研究结果表明, n-back工作记忆训练可以提高幼儿的流体智力成绩, 并且这种训练效果具有持续的稳定性。     

The relationship between n-back performance and matrix reasoning — implications for training and transfer

We have previously demonstrated that training on a dual n-back task results in improvements in fluid intelligence (Gf) as measured by matrix reasoning tasks. Here, we explored the underlying mechanisms of this transfer effect in two studies, and we evaluated the transfer potential of a single n-back task. In the first study, we demonstrated that dual and single n-back task performances are approximately equally correlated with performance on two different tasks measuring Gf, whereas the correlation with a task assessing working memory capacity was smaller. Based on these results, the second study was aimed on testing the hypothesis that training on a single n-back task yields the same improvement in Gf as training on a dual n-back task, but that there should be less transfer to working memory capacity. We trained two groups of students for four weeks with either a single or a dual n-back intervention. We investigated transfer effects on working memory capacity and Gf comparing the two training groups' performance to controls who received no training of any kind. Our results showed that both training groups improved more on Gf than controls, thereby replicating and extending our prior results.     

个体差异对工作记忆训练迁移效果的调节

本研究考察了流体智力基线水平对工作记忆训练迁移效果的影响。采用前后测设计,以视觉和听觉双任务n-back作为工作记忆训练任务,对训练组进行为期一个月的训练;积极对照组采用阅读任务进行训练。结果发现积极控制组的流体智力水平在基线与后测之间无显著变化;而训练组流体智力水平在后测时与基线相比有显著提高,且工作记忆训练提升量越大的个体其流体智力改善越大。说明认知训练有效迁移到了流体智力水平的改善上。我们还发现流体智力基线水平调节了工作记忆训练对流体智力水平的迁移,即工作记忆训练提升量越大,流体智力改善值越大,对于那些流体智力基线水平较高的人来说,工作记忆训练对流体智力改善的效果更大。流体智力基线水平、工作记忆训练提升量及两者的乘积共同影响了流体智力改善值。这一结果表明个体差异如流体智力基线水平可以调节工作记忆训练对流体智力水平的迁移。     

3D Multiple Object Tracking Boosts Working Memory Span: Implications for Cognitive Training in Military Populations

Recently, there has been much theoretical and applied interest in the prospects of cognitive training for improving cognition. NeuroTracker is a relatively recent training device for improving dynamic attention in athletes by training 3D multiple-object tracking skills. We examined its effectiveness for improving working memory (WM) span in members of the Canadian Armed Forces (CAF) by randomly assigning participants to the experimental (NeuroTracker), active control (adaptive dual n-back task), or passive control (no contact) conditions. NeuroTracker training resulted in significant gains in verbal, visual, and matrix span. No gain was observed in the active or passive control group. These results suggest that NeuroTracker could be a useful training tool for increasing WM span in military samples. Future studies could examine the effects of NeuroTracker training on militarily relevant performance measures that draw on WM span.     

N-backer: an auditory n-back task with automatic scoring of spoken responses

The n-back task is commonly used to load working memory (WM) in dual-task and neuroimaging experiments. However, it typically involves visual presentation and buttonpress responses, making it unsuitable for combination with primary tasks that involve vision and action, such as sequential object use and other tasks of daily living. The N-backer software presented here will automatically present and score auditory–verbal n-back sequences utilising the standard speech synthesis and recognition facilities that come with Microsoft Windows. Data are presented from an experiment in which 12 student participants carried out three tasks from the Naturalistic Action Test (NAT) while their attention was divided between the primary task and a continuous auditory–verbal 2-back secondary task. The participants’ 2-back performance was scored in two ways: by hand, from video recordings, and automatically, using the software, allowing us to evaluate the accuracy of N-backer. There was an extremely high correlation between these scores (.933). The videos were also used to obtain a comprehensive error score for the NAT. Significantly more errors were made in the more complex NAT tasks when participants were 2-backing, as compared with when they were not, showing that the auditory–verbal n-back task can be used to disrupt sequential object use. This dual-task method may simulate the attentional deficits of patients with brain injury, providing insights into the difficulties they face in tasks of daily living.     

Exploring possible neural mechanisms of intelligence differences using processing speed and working memory tasks: An fMRI study

To explore the possible neural foundations of individual differences in intelligence test scores, we examined the associations between Raven's Matrices scores and two tasks that were administered in a functional magnetic resonance imaging (fMRI) setting. The two tasks were an n-back working memory (N = 37) task and inspection time (N = 47). The subjects were members of the Aberdeen Birth Cohort 1936, aged in their mid–late 60s when tested for this study. Performance on both tasks was correlated significantly with scores on Raven's Matrices. In the inspection time task there were regions with significant correlations between the neural activity (BOLD response) and performance but not between BOLD response and scores on Raven's Matrices. In the working memory task there were no significant correlations between BOLD response and either performance or scores on Raven's Matrices. Moreover, there was almost no mediation of the Raven's Matrices versus n-back and inspection time scores correlations by the respective BOLD response. These findings partially replicate important aspects of a prominent report in this field [Gray, J.R., Chabris, C.F., & Braver, T.S. (2003). Neural mechanisms of general fluid intelligence. Nature Neuroscience, 6, 316–322.], but have also extended the those finding into both a unique population and a novel functional task.     

The Relationship between Performance in Near Match-to-Sample Tasks and Fluid Intelligence

Match-to-sample is a timed task in which a subject is presented with a visual stimulus (the probe) and must select a match to that stimulus (the target) from among an array of distractors. These tasks are frequently employed as tests of basic cognitive abilities and demonstrate consistent correlations with measures of intelligence. In the current study, a match-to-sample task was modified to produce near-match conditions (trials for which no exact match existed). Two factors were manipulated: type of discrepancy between the target and probe (additive or subtractive) and degree of discrepancy between target and probe (1 element or 2 elements). It was hypothesized that introducing near-match conditions would change the processing demands of the task, resulting in increased correlations between decision time and fluid intelligence. Degree and type of discrepancy affected decision times: participants required more time for 2 element discrepancies and additive type discrepancies. Contrary to expectations, increased decision time on a task did not correspond to higher correlations with fluid intelligence. For type, correlations were larger when participants needed to mentally subtract elements from the target in order to make it match the probe (mean r_additive = .399; mean r_subtractive = .451). For degree, correlations were larger for trials where the probe and target differed by one element (mean r = .470) than for trials where the probe and target differed by two elements (mean r = .380). These results seem to indicate that the relationship between the complexity of a task and general intelligence is not as straightforward as has been commonly believed.     

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.     

Working memory training improvements and gains in non-trained cognitive tasks in young and older adults

Previous studies on working memory training have indicated that transfer to non-trained tasks of other cognitive domains may be possible. The aim of this study is to compare working memory training and transfer effects between younger and older adults (n = 60). A novel approach to adaptive n-back training (12 sessions) was implemented by varying the working memory load and the presentation speed. All participants completed a neuropsychological battery of tests before and after the training. On average, younger training participants achieved difficulty level 12 after training, while older training participants only reached difficulty level 5. In younger participants, transfer to Verbal Fluency and Digit Symbol Substitution test was found. In older participants, we observed a transfer to Digit Span Forward, CERAD Delayed Recall, and Digit Symbol Substitution test. Results suggest that working memory training may be a beneficial intervention for maintaining and improving cognitive functioning in old age.     

Individual differences in media multitasking and performance on the <Emphasis Type="Italic">n</Emphasis>-back

A number of studies have recently examined the link between individual differences in media multitasking (using the MMI) and performance on working memory paradigms. However, these studies have yielded mixed results. Here we examine the relation between media multitasking and one particular working memory paradigm—the n-back (2- and 3-back)—improving upon previous research by (a) treating media multitasking as a continuous variable and adopting a correlational approach as well as (b) using a large sample of participants. First, we found that higher scores on the MMI were associated with a greater proportion of omitted trials on both the 2-back and 3-back, indicating that heavier media multitaskers were more disengaged during the n-back. In line with such a claim, heavier media multitaskers were also more likely to confess to responding randomly during various portions of the experiment, and to report media multitasking during the experiment itself. Importantly, when controlling for the relation between MMI scores and omissions, higher scores on the MMI were associated with an increase in false alarms, but not with a change in hits. These findings refine the extant literature on media multitasking and working memory performance (specifically, performance on the n-back), and suggest that media multitasking may be related to the propensity to disengage from ongoing tasks.     

Age-specific differences of dual n-back training

Age-related decline in executive functions can be decisive in performing everyday tasks autonomously. Working memory (WM) is closely related to executive functions, and training of WM has yielded evidence toward cognitive plasticity in older adults. The training effects often transfer to untrained tasks and functions. These effects have mostly been shown in processes such as WM and attention, whereas studies investigating transfer to executive functions have been scarce. We trained older adults aged 57–73 years in a WM training task that was reported to be effective in producing transfer in young adults. The training intervention consisted of a dual n-back task including independently processed auditory and visual n-back tasks. We investigated transfer to tasks engaging executive functions, and compared the effects in older adults to those reported in young adults. We found that both training groups improved in the training task. Although the training effect in older adults was smaller than the training effect in young adults, the older adults still showed a notable improvement so that after training they performed on the same level as young adults without training. The older adults also showed transfer to an untrained WM updating task, a result that was in accordance with the findings in young adults; other transfer effects in older adults were lacking. We conclude that although transfer effects were scarce, the present study provides encouraging evidence toward the possibilities to compensate for age-related decline in executive functions by a WM training intervention.     

Selling points: What cognitive abilities are tapped by casual video games?

The idea that video games or computer-based applications can improve cognitive function has led to a proliferation of programs claiming to “train the brain.” However, there is often little scientific basis in the development of commercial training programs, and many research-based programs yield inconsistent or weak results. In this study, we sought to better understand the nature of cognitive abilities tapped by casual video games and thus reflect on their potential as a training tool. A moderately large sample of participants (n = 209) played 20 web-based casual games and performed a battery of cognitive tasks. We used cognitive task analysis and multivariate statistical techniques to characterize the relationships between performance metrics. We validated the cognitive abilities measured in the task battery, examined a task analysis-based categorization of the casual games, and then characterized the relationship between game and task performance. We found that games categorized to tap working memory and reasoning were robustly related to performance on working memory and fluid intelligence tasks, with fluid intelligence best predicting scores on working memory and reasoning games. We discuss these results in the context of overlap in cognitive processes engaged by the cognitive tasks and casual games, and within the context of assessing near and far transfer. While this is not a training study, these findings provide a methodology to assess the validity of using certain games as training and assessment devices for specific cognitive abilities, and shed light on the mixed transfer results in the computer-based training literature. Moreover, the results can inform design of a more theoretically-driven and methodologically-sound cognitive training program.     

Behavioural and ERP Effects of Cognitive and Combined Cognitive and Physical Training on Working Memory and Executive Function in Healthy Older Adults

Cognitive and physical training have been shown to be effective in improving older adults’ cognition. However, it is not yet clear whether combined cognitive and physical training offers an advantage compared to cognitive training alone. Twenty-two older adults performed cognitive or combined cognitive and physical training in order to compare their effects on working memory event-related potentials (ERPs) and on working memory and executive function performance. Before and after eight weeks of training, performance in Plus Minus, Flanker, Updated Span, and Complex Span tasks was measured, and ERPs were registered during performance of an n-back task (0-back, 2-back, and 3-back). Post-training behavioural improvement was observed in Updated Span, Complex Span, and n-back tasks. During the n-back task, the N2/P3 complex was modulated by training, with a decrease in N2 amplitude and an increase in P3 amplitude in the posttraining session compared to the pretraining session. These changes in ERP components suggest that both types of training potentially reduce the need for attentional control to perform the tasks correctly and increase working memory capacity. Thus, based on our data, no conclusion can be reached on the direct advantage of combined training, either at behavioural or at neural level. However, the present study might suggest an indirect advantage of such a combined training, because the cognitive benefit was found to be highly similar in both types of training. Using combined cognitive and physical training may produce a potential improvement in general fitness and an increased appeal of training.     

Does it deliver what it promises? Evaluation of cognitive distraction caused by speech-based interfaces with detection response and box task

Speech is considered a promising modality for human-machine interaction while driving, especially in reducing visual and manual distraction. However, speech-based user interfaces themselves have shown to increase cognitive distraction. There remains a lack of standardized and unambiguous methods for measuring the impact of speech-based assistants on cognitive distraction while driving. This work aims to investigate whether the combination of the box task and the detection response task (DRT) is a suitable method for assessing the cognitive distraction caused by speech-based assistants. For this purpose, participants (N = 39) engaged in artificial (n-back tasks) and natural speech-based secondary tasks (interaction with Android’s Google Assistant and Apple's Siri) differing in predefined levels of cognitive workload while performing the box task and the DRT. The results showed that DRT performance differed between the 0-back and 1-back task but not between the different cognitive workload levels of the speech-based assistants. No clear effects emerged for the box task parameters. Thus, the combination of the box task and DRT is well-suited for measuring cognitive distraction caused by artificial secondary tasks but not by natural interactions with speech-based assistants.     

Working memory, attention control, and the N-back task: a question of construct validity

The N-back task requires participants to decide whether each stimulus in a sequence matches the one that appeared n items ago. Although N-back has become a standard "executive" working memory (WM) measure in cognitive neuroscience, it has been subjected to few behavioral tests of construct validity. A combined experimental- correlational study tested the attention-control demands of verbal 2- and 3-back tasks by presenting n = 1 "lure" foils. Lures elicited more false alarms than control foils in both 2- and 3-back tasks, and lures caused more misses to targets that immediately followed them compared with control targets, but only in 3-back tasks. N-back thus challenges control over familiarity-based responding. Participants also completed a verbal WM span task (operation span task) and a marker test of general fluid intelligence (Gf; Ravens Advanced Progressive Matrices Test; J. C. Raven, J. E. Raven, & J. H. Court, 1998). N-back and WM span correlated weakly, suggesting they do not reflect primarily a single construct; moreover, both accounted for independent variance in Gf. N-back has face validity as a WM task, but it does not demonstrate convergent validity with at least 1 established WM measure.     

How am I doing? Performance feedback mitigates the effects of mental fatigue on endurance exercise performance

Mental fatigue induced by an earlier cognitive task can impair performance on a subsequent physical task. The current study investigated whether such performance impairment could be mitigated by performance feedback. In an experimental sequential-task design, 63 sport science students completed a series of three tasks: 5-min physical (pre-test), 20-min cognitive, 5-min physical (post-test). Participants were randomly allocated to one of three groups: feedback (n = 23), no feedback (n = 20), control (n = 20). The physical tasks, which assessed force production during a self-paced rhythmic handgrip task as a measure of physical endurance performance, were performed with (feedback group) or without (no feedback group, control group) visual performance feedback. The cognitive tasks involved either completing a 2-back memory task to induce mental fatigue (feedback and no feedback groups) or watching a didactic film (control group). Self-report measures (fatigue, exertion, vigor, motivation) were collected throughout. The 2-back cognitive task increased mental fatigue, mental exertion and general fatigue in the feedback and no feedback groups compared to the control group. Relative to the pre-test physical task, post-test endurance performance declined in the no feedback group (−14.4%) but did not change in the control (−2.6%) and feedback (−2.4%) groups. This mitigation of performance effect was not accompanied by parallel changes in fatigue, exertion, vigor, or motivation. In conclusion, visual performance feedback mitigates the negative effects of mental fatigue on physical endurance performance.