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Just what are fMRI scans supposed to be ‘proving’?

Why We Remain Optimistic In The Face Of Reality Revealed By Brain Imaging

I won’t go into the detail of the study this time, because you can follow the link to a nice clear press release (and I want to get on with my rant), but it was basically about how people are likely to modify their idea of the chances of something bad happening if they’re presented with evidence that it’s less likely than they thought, but less likely to modify their judgement if the evidence suggests it’s more likely than they thought – a mechanism for optimism in the face of disconfirming evidence from the world (something we all need). I haven’t explained that well – the original is clearer.

But the bit I want to go on about is the interpretation of the research. People were observed making these ‘reasonably’ and ‘unreasonably’ optimistic judgements in an fMRI scanner, and different decisions were associated with different activity if the frontal cortex. They also looked to see if people who scored higher on an ‘optimism’ questionnaire showed different brain activity.
The results show:

… that our failure to alter optimistic predictions when presented with conflicting information is due to errors in how we process the information in our brains.


….the more optimistic a participant was (according to the personality questionnaire), the less efficiently activity in these frontal regions coded for it, suggesting they were disregarding the evidence presented to them.

“The less efficiently activity in these frontal regions coded…”? – just what kind of ‘coding’ are we talking about here? What does ‘efficient’ coding mean: what’s efficient and inefficient (not in psychologically using the information: we’re not talking about that here, but in coding in the frontal cortex)? And just what is the evidence for that? Some bits of the frontal cortex are more active than others, I guess – but even if we knew functionally what ‘efficient coding’ was, I don’t think that we know anything about how that shows itself in brain activity.

And the final sentence of the quote is the most exasperating: ‘suggesting they were disregarding the evidence presented to them’. You needed a fancy fMRI machine to tell you that? You’d already established that with pencil and paper: you presented them with information and they disregarded it – you DON’T need fMRI to tell you that what you’ve just solidly observed in other ways ‘really’ happens.

Think of it the other way round, what if you did know how to identify ‘efficient coding’ in the frontal cortex, and you did this study and found that the more optimistic respondents (who have, behaviourally, already ’disregarded the evidence’) didn’t show any difference, would you say this suggests that ‘they DON’T disregard the evidence presented to them’? That would be nonsense. So the final sentence in the quote above adds absolutely nothing to our psychological understanding.

Don’t get me wrong. Like Dobbs, I’m not saying fMRI studies are rubbish – but as a psychologist, I am really exasperated by the way some people talk about fMRI studies as a way of ‘proving’ what we already know perfectly well, and have demonstrated perfectly well, as psychologists – when those fMRI studies don’t yet add anything to our understanding. And it is worrying if these high-powered researchers make what seem to me to be elementary logical errors in their statements – maybe they’re not rocket scientists after all.


One response to “Just what are fMRI scans supposed to be ‘proving’?

  1. Pingback: One of the foundation myths of modern psychology: “Brain Scans Show” « millerpsych

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