In my last post I outlined the differences between fluid and crystallised intelligence and argued that fluid intelligence (Gf) – the ability to reason and to solve new problems independently of previously acquired knowledge – is fairly fixed, whereas crystallised intelligence (Gc) – the ability to retrieve  and apply information stored in long-term memory can be improved relatively straightforwardly by teaching students knowledge and then giving them practice in retrieving and applying this knowledge in a variety of contexts.

This is a shame because as Daniel Willingham says in Why Don’t Students Like School?

The lack of space in working memory is a fundamental bottleneck of human cognition… if a genie comes out of a lamp and offers you one way to improve your mind, ask for more working memory capacity. People with more capacity are better thinkers, at least for the type of thinking done in school. (p. 109)

Since writing, Geoff Petty got in touch to suggest that such a genie might exist, and that there’s evidence that we can, in fact, increase fluid intelligence through specialised ‘brain training’ programmes. He sent me this article by Robert Sternberg which states that, “Fluid intelligence is trainable to a significant and meaningful degree.” Sternberg is writing about a 2008 study conducted by Jaeggi et al (£) in which the authors make the following claim:

Here, we present evidence for transfer from training on a demanding working memory task to measures of Gf. This transfer results even though the trained task is entirely different from the intelligence test itself. Furthermore, we demonstrate that the extent of gain in intelligence critically depends on the amount of training: the more training, the more improvement in Gf. That is, the training effect is dosage-dependent. Thus, in contrast to many previous studies, we conclude that it is possible to improve Gf without practicing the testing tasks themselves, opening a wide range of applications.

Sounds encouraging, doesn’t it? Sternberg certainly thinks so:

Jaeggi et al.’s article  is important to the field of intelligence because it shows that training can improve fluid intelligence, can do so across intelligence levels, and can do so in a theory based way. To the extent that past investigators failed to obtain such robust results, it appears to be because they failed to use the cognitive–theoretical basis that served as the basis for training in Jaeggi et al.’s study. These results have important educational-policy implications, because they suggest that the results of conventional tests of intellectual abilities and aptitudes provide indices that may be dynamic rather than static and modifiable rather than fixed. Most researchers have viewed intelligence as largely fixed, although others have argued strongly for its modifiability. The latter are shown to be justified in their beliefs.

Now, as we all know, Carol Dweck rode in on her white charger to reveal that ‘the brain is like a muscle’ and that we can all be as clever as we make our minds up to be as long as we have the requisite mindset. Any evidence to the contrary is evidence of a fixed mindset. Before we go on to consider these specific claims about fluid intelligence, let’s remind ourselves that of course intelligence is malleable: we can always learn more stuff to help us cheat our working memory’s limitations.

We’ve known for ages that practising mental arithmetic improves our ability to do mental arithmetic. Similarly, if you practise memorising the order of a deck of shuffled card, you get better at that and if you practise playing brain training games you can become significantly better at playing brain training games. But these improvements don’t seem to transfer. But, the specific claim of Jaeggi et al’s research is that by engaging in a specialised form brain training programme, an increase in working memory capacity can be transferred across domains.

In this 2009 rebuttal, David Moody throws cold water on our hopes, saying, “A close examination of the evidence reported by Jaeggi et al. shows that it is not in fact sufficient to support the authors’ conclusion of any increase in their subjects’ fluid intelligence.” Moody’s quite critical of the way in which the tests were designed and administered and points out that far from being the training exercises being “entirely different” from the tests, some actually seem to have been “well-designed to facilitate performance on that test.” He concludes by saying, “Whatever the meaning of the modest gains in performance… the evidence produced by Jaeggi et al. does not support the conclusion of an increase in their subjects’ intelligence.”

This is a debate which has rattled on. 2013, saw a report from Harrison et al which concluded, “It is becoming very clear that training on working memory with the goal of trying to increase Gf will likely not succeed.” Whereas in 2014, Jaeggi was part of a team which conducted a meta analysis into improving fluid intelligence with training on working memory and found that “it is becoming very clear to us that training on WM with the goal of trying to increase Gf holds much promise.”

Most recently, this comprehensive review by Daniel Simons and colleagues published in Psychological Science in the Public Interest, attempts to put the matter beyond doubt. They found

…extensive evidence that brain-training interventions improve performance on the trained tasks, less evidence that such interventions improve performance on closely related tasks, and little evidence that training enhances performance on distantly related tasks or that training improves everyday cognitive performance. We also find that many of the published intervention studies had major shortcomings in design or analysis that preclude definitive conclusions about the efficacy of training, and that none of the cited studies conformed to all of the best practices we identify as essential to drawing clear conclusions about the benefits of brain training for everyday activities. [my emphasis]

The answer seems very clear. To the best of our current knowledge, brain training programmes boost performance in brain training programmes but do not result in a generalisable increase in working memory capacity and do not increase fluid intelligence.

That might be that except that some people want to argue there’s more to intelligence than working memory capacity and that teaching ‘thinking skills’ would be a productive way forward.

In my next post I’ll examine the claims of ‘cognitive acceleration’ to see whether they present a viable alternative to a focus on improving crystallised intelligence through a knowledge-rich curriculum.