DISCOVER: Can Brain Scans Detect Pedophiles?

What’s the News: A new study suggests that watching brain activity when subjects are shown images of naked children can identify which are pedophiles. But what does this really mean in practical terms?

How the Heck:

24 self-identified pedophiles, from a clinic that offers anonymous treatment, and 32 male controls were shown pictures of naked men, women, and children. Blogger Neuroskeptic, who brought this study to the web’s attention, notes in an aside that getting that past a university ethics board is quite a coup.
Using fMRI, the researchers recorded their brains’ responses and found that by comparing an individual’s brain to the average of the pedophiles and the average of the controls, they could assign them to the correct group more than 90% of the time. Their handling of the statistics avoids the most obvious pitfalls: they used an analyses technique called leave-one-out cross-validation to avoid comparing a given scan to an average that includes it, a common error in neuro studies.
When they plotted how the neural scans lined up along the age and sex axes (see image above), the pedophile and control scans formed two clear, separate clusters.

--snip--

The Future Holds: Realistically, we can’t judge people on their biological red flags—whether it’s brain scans or genetics—without entering a Minority Report-style future. That’s because being attracted to children isn’t a crime. Acting on it is. Generally, a brain scan is not required to find out whether the crime has happened—there are other, more reliable forms of evidence, like porn downloads. Given that, it’s unlikely that you’ll be seeing regular scanning for pedophilic tendencies anytime soon. And for that, we should be grateful.

At the conference at which this diagnostic note was first presented, I asked with what
accuracy, based only on the images of myelination, one could accurately distinguish the individual
brains of sixteen and seventeen year olds on the one hand and eighteen and nineteen year olds on the
other. One neuroscientist claimed that the scientist could do this with great accuracy if the scientist
were furnished with the sex and handedness of the subject. This claim would have been quite
believable if the comparison groups were thirteen and fourteen year olds versus twenty-five and
twenty-six year olds, but it seemed doubtful to me because development is continuous and the groups
were so close in age. After the conference, I therefore asked the question of other equally
credentialed and experienced neuroscientists and neuroanatomists. My informants uniformly agreed
that they could not very accurately distinguish sixteen and seventeen year old brains from eighteen
and nineteen year old brains. I do not know who is right. To the best of my knowledge, a study to
determine accuracy of this type has not been performed, but the outcome would be very interesting.