Adrian Raine, Ph.D., led a team that compared brain activity in 22 murderers and 22 normal folks. Their tool of choice: the PET scan, an imaging technique that measures the brain's utilization of glucose, its primary fuel. The scans indicate which areas of the brain are active--and which are lying low.
The researchers discovered that the prefrontal cortex, the brain region right behind the forehead, was less active in the murderers. Prefrontal deficiencies have been associated with a variety of behaviors--risk taking, rule breaking, aggression, and impulsivity--that can lead to violence.
If further studies confirm that murderers' brains are biologically different, does this mean that some of us are natural born killers? Not at all. Raine, who says his own brain scan resembles that of a man who killed 43 people, thinks that biological and environmental factors are both essential components of violent behavior.
But the idea that killers' brains are different has profound implications for justice--and for rehabilitation. Cognitive remediation training has helped brain-injured patients recover lost function. If such therapy is able to help violent offenders beef up their brain to compensate for an underactive prefrontal cortex, the changes might show up on a PET scan. Come parole time, those scans could be far more convincing evidence of rehabilitation than a convict's professed remorse.