Ben Goldacre

The Guardian

Saturday November 17 2007

Obviously we’re all interested in who the next US president is going to be, since it affects our risk of being blown up on the bus to work. According to the New York Times – which has covered this story at least three times – a commercial company which specialises in giving brain images to advertisers has discovered which parts of a voter’s brain are most activated by different candidates, by taking pictures of their brains while they supposedly think about them.

Functional brain imaging is a great idea. Your brain is made up of lots of different areas, which often seem to do different jobs, and you can determine that in all kinds of different ways. For example, Broca’s area (near the front on the left) seems to be involved in generating language: it is often knocked out in strokes, and when it goes, you have difficulty speaking, but you can still hear and understand language fine, because the part of the brain that receives and decodes speech is still intact. The motor cortex (in an arc from above your ear to the top of your head) contains a map of all the parts of your body, and if you stimulate it, by taking your skull off with a circular saw and giving it a small electric shock with a battery, the associated part of your body will twitch.

Brain imaging is a less destructive way of examining the brain: you perform a task, while lying inside a scanner, and the parts of your brain which are most active during that task light up, because they are doing more work, and so receiving more blood flow.

Brain imaging experiments are designed to constrain activity in the brain, so that the results are meaningful: for example, you might give two tasks where the only difference between them is the use of one faculty. You might compare “lift each finger in order from left to right” against “lift each finger in whatever order you fancy” as a basic microcosm of which bits of the brain become more active when you have to make a decision. But if you just show someone the word “republican”, God knows what’s going on in their head. They might be smirking with schadenfreude at how loopy the Christian right are. They might be feeling angry about them. They might be rehearsing the word repeatedly and determinedly on their internal phonological loop, thinking that they’re being helpful.

In fact, lots of parts of your brain will light up in brain imaging studies and it’s tempting to over-extrapolate, selling activation locations as supporting your favoured hypothesis, while ignoring all kinds of alternative interpretations.

And that’s in proper research. Here, they showed people a picture of Democratic nominee John Edwards. “Subjects who had rated him low on the thermometer scale showed activity in the insula, an area associated with disgust and other negative feelings.” But the insula is a large area, with different bits activated in many tasks, including balance, pain, all kinds of stuff.

“The good news for Mr Edwards is that the swing voters who did not give him low ratings, when looking at still photos of him, showed significant activation in areas of the brain containing mirror neurons – cells that are activated when people feel empathy. And that suggests these voters feel some connection to him.” This is a fanciful view of mirror neurons (I wish I had space to tell you about them; they’re more interesting than anything in any newspaper) but even if we leave that aside, there are several regions containing mirror neurons, and those areas also contain lots of other neurons which, well, do not respond like mirror neurons.

They don’t tell us how many subjects were in each group, what the tasks were, how they correlated with scores on their preferences, or indeed anything useful. With science, you publish a description of your experiments, in an academic journal, so that people can see what you’ve done, not your interpretation. That is why academic journals exist, instead of just newspapers, and that is why a huge posse of proper professors of cognitive neuroscience have waded in and sent a long, angry letter to the NYT, not over politics, or a view, but simply over the importance of ideas.