Thursday, 14 February 2013
Working memory describes our ability to hold relevant information in mind for use in mental tasks, while ignoring irrelevant information. If it were possible to improve our working memory capacity and discipline through training, it makes sense that this would have widespread benefits. But that's a big if.
A new meta-analysis by Monica Melby-Lervåg and Charles Hulme has just been published in the February issue of the respected APA journal Developmental Psychology, which combined the results from 23 studies of working memory training completed up to 2011 (PDF is freely available). To be included, studies had to compare outcomes for a working memory training treatment group against outcomes in a control group. Most of the studies available are on healthy adults or children, with just a few involving children with developmental conditions such as ADHD.
The results were absolutely clear. Working memory training leads to short-term gains on working memory performance on tests that are the same as, or similar to, those used in the training. "However," Melby-Lervåg and Hulme write, "there is no evidence that working memory training produces generalisable gains to the other skills that have been investigated (verbal ability, word decoding, arithmetic), even when assessments take place immediately after training."
There was a modest, short-term benefit of the training on non-verbal intelligence but this disappeared when only considering the studies with a robust design (i.e. those that randomised participants across conditions and which enrolled control participants in some kind of activity). Similarly, there was a modest benefit of the training on a test of attentional control, but this disappeared at follow-up.
All of this suggests that working memory training isn't increasing people's working memory capacity in such a way that they benefit whenever they engage in any kind of task that leans on working memory. Rather, people who complete the training simply seem to have improved at the specific kinds of exercises used in the training, or possibly even just at computer tasks - effects which, anyway, wear off over time.
Overall, Melby-Lervåg and Hulme note that the studies that have looked at the benefits of working memory training have been poor in design. In particular, they tend not to bother enrolling the control group in any kind of intervention, which means any observed benefits of the working memory training could be related simply to the fun and expectations of being in a training programme, never mind the specifics of what that entails. Related to that, some dubious studies reported far-reaching benefits of the working memory training, without finding any improvements in working memory, thus supporting the notion that these benefits had to do with participant expectations and motivation.
A problem with all meta-analyses, this one included, is that they tend to rely on published studies, which means any unpublished results stuck in a filing cabinet get neglected. But of course, it's usually negative results that get left in the drawer, so if anything, the current meta-analysis presents an overly rosy view of the benefits of working memory training.
Melby-Lervåg and Hulme's ultimate conclusion was stark: "there is no evidence that these programmes are suitable as methods of treatment for children with developmental cognitive disorders or as ways of effecting general improvements in adults' or children's cognitive skills or scholastic achievements."
Melby-Lervåg M, and Hulme C (2013). Is working memory training effective? A meta-analytic review. Developmental psychology, 49 (2), 270-91 PMID: 22612437 Free, full PDF of the study.
This meta-analysis only took in reviews published up to 2011. If you know of any quality studies into the effects of working memory training published since that time, please do share the relevant links via comments.
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Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.