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In a twist that evokes the dystopian science fiction of writer Philip K. Dick, neuroscientists have found a way to predict whether convicted felons are likely to commit crimes again from looking at their brain scans. Convicts showing low activity in a brain region associated with decision-making and action are more likely to be arrested again, and sooner.

Kent Kiehl, a neuroscientist at the non-profit Mind Research Network in Albuquerque, New Mexico, and his collaborators studied a group of 96 male prisoners just before their release. The researchers used functional magnetic resonance imaging (fMRI) to scan the prisoners’ brains during computer tasks in which subjects had to make quick decisions and inhibit impulsive reactions.

The scans focused on activity in a section of the anterior cingulate cortex (ACC), a small region in the front of the brain involved in motor control and executive functioning. The researchers then followed the ex-convicts for four years to see how they fared.

Among the subjects of the study, men who had lower ACC activity during the quick-decision tasks were more likely to be arrested again after getting out of prison, even after the researchers accounted for other risk factors such as age, drug and alcohol abuse and psychopathic traits. Men who were in the lower half of the ACC activity ranking had a 2.6-fold higher rate of rearrest for all crimes and a 4.3-fold higher rate for nonviolent crimes. The results are published today in the Proceedings of the National Academy of Sciences1.

There is growing interest in using neuroimaging to predict specific behaviour, says Tor Wager, a neuroscientist at the University of Colorado in Boulder. He says that studies such as this one, which tie brain imaging to concrete clinical outcomes, “provide a new and so far very promising way” to find patterns of brain activity that have broader implications for society.

But the authors themselves stress that much more work is needed to prove that the technique is reliable and consistent, and that it is likely to flag only the truly high-risk felons and leave the low-risk ones alone. “This isn't ready for prime time,” says Kiehl.

Wager adds that the part of the ACC examined in this study “is one of the most frequently activated areas in the human brain across all kinds of tasks and psychological states”. Low ACC activity could have a variety of causes — impulsivity, caffeine use, vascular health, low motivation or better neural efficiency — and not all of these are necessarily related to criminal behaviour.

Crime prediction was the subject of Dick's 1956 short story “The Minority Report” (adapted for the silver screen by Steven Spielberg in 2002), which highlighted the thorny ethics of arresting people for crimes they had yet to commit.

Brain scans are of course a far cry from the clairvoyants featured in that science-fiction story. But even if the science turns out to be reliable, the legal and social implications remain to be explored, the authors warn. Perhaps the most appropriate use for neurobiological markers would be for helping to make low-stakes decisions, such as which rehabilitation treatment to assign a prisoner, rather than high-stakes ones such as sentencing or releasing on parole.

“A treatment of [these clinical neuroimaging studies] that is either too glibly enthusiastic or over-critical,” Wager says, “will be damaging for this emerging science in the long run.”