More exercise = more I.Q.?

Interesting post by Gretchen Reynolds reviewing the evidence on exercise and intelligence. The title is “Phys Ed: Can Exercise Make Kids Smarter?”, so this is definitely seen as something which is “actionable” in a public policy sense, especially in light of the increases in obesity among young people. Intuitively I think most people are going to agree with this in the United States. In fact, when you’re down with the flu or some other illness you are generally less productive (most of the films I’ve watched over the past three years have been when I’m ill since I can’t focus on difficult material), so there’s probably going to be a natural connection made between greater cognitive function with greater health.

First, Reynolds points to a study which shows that:

1) The most fit children are more intelligent than the least fit as adduced from psychometric tests

2) The most fit children ‘had significantly larger basal ganglia, a key part of the brain that aids in maintaining attention and “executive control,” or the ability to coordinate actions and thoughts crisply.’ The researchers controlled for socioeconomic status and body mass index,

A second study indicated that the fit children had better working memory and greater hippocampal volume. Finally, an earlier study using data from Swedish conscripts showed that even among identical twins the fitter ones were more intelligent. Note that the primary author was the same on the first two studies. Before commenting further how about looking at some tables and/or figures from the papers?

The first image has two tables from the first paper, the second two images are from the second paper, and finally, the last is from the last paper.

As most of you know just because papers make it through peer review doesn’t imply that they’re going to stand the test of time. Over the years I’ve also gotten more and more skeptical of neuroimaging results, primarily because there’s now psychological evidence that images of brains add to the credibility of research in a very irrational fashion. To really understand the first two studies you probably have to be a cognitive neuroscientist, in particular, one with some background in psychometrics. The last study is more straightforward as you’re comparing dizygotic and monozygotic twins, and seeing the correlations between traits as a function of genetic relatedness. The latter are genetically identical, in theory if not totally in practice, so one presumes that the differences may be environmental.

Perhaps, but it depends on what you label “environment.” We may be seeing differences which derive from random events in the fetal environment, or during early stages of development. Aspects of fitness are often correlated. If athletic and intellectual prowess are both embedded in numerous genetic and physiological pathways, which seem likely, then variations due to stochastic aspects of development may affect both trait clusters in the same fashion.

In other words I’d say to make a strong case for the efficacy of exercise and aerobic health as a driver of higher intelligence we should wait for more research. On the other hand there are plenty of data on the value of aerobic health more generally, and the downsides of obesity, so there are other grounds on which to move forward. I suspect if these sorts of studies get into the Zeitgeist you’ll have pretty dumb books published soon with titles like “How 1 hour of exercise a day can give you 10 I.Q. points! (as shown by studies!)”.

Note: A quick lit search yields papers like this, so I’m not totally clear that there are robust long term cognitive benefits to exercise, though in some cases there seems to be.

Image Credit: Michael Schmalenstroer