Home » Mind, Neuroscience, News » There is something wrong with the popular idea of what brain scans can tell us if …

There is something wrong with the popular idea of what brain scans can tell us if …

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… they are getting signals from dead fish.

In “the trouble with brain scans” (The Guardian Observer, May 27, 2012), psychiatrist Vaughan Bell tells us, “Many of the methods on which brain scan studies are based have been flawed – as one image of a dead salmon proved”:

All of our experiences and abilities rely on a distributed brain network and nothing relies on a single “centre”. More than anything, the conclusions depend on the tasks volunteers undertake in the scanner and what each study tells us is limited. This small print has been repeated many times over by scientists. They bemoan how people misunderstand the subtleties and draw unwarranted conclusions. But now neuroscientists have had to come to terms with the fact that many of the methods on which brain scan studies are based have been flawed.

When we’re talking about millions of comparisons, a big problem is false positives. Imagine you are playing two roulette wheels. Clearly, the result of one doesn’t affect the outcome of the other but sometimes they’ll both come up with the same number just due to chance. Now imagine you have a roulette wheel for every point or voxel in the brain. A comparison of any two scans could look like some areas show linked activity when really there is no relationship. Ideally, the analysis should separate roulette wheels from genuine activity, but you may be surprised that hundreds if not thousands of studies have been conducted without such corrections. To illustrate the problem, Craig Bennett and his colleagues at the University of California did a spoof experiment on a dead salmon. The standard techniques showed “brain activity” in the deceased fish.

Either – as commenters joked – this is evidence of life after death in deceased fish, or pop science journalism should go on a conceptual diet of some kind.

Hat tip: Stephanie West Allan at Brains on Purpose

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2 Responses to There is something wrong with the popular idea of what brain scans can tell us if …

  1. “A comparison of any two scans could look like some areas show linked activity when really there is no relationship. Ideally, the analysis should separate roulette wheels from genuine activity, but you may be surprised that hundreds if not thousands of studies have been conducted without such corrections.”

    Hmmm….. Reminds me of this:

    Statistical Significance on XKCD

  2. 2

    This is animal cruelty. Don’t beat a dead fish.

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