New Scientist reviews Adrian Raine’s The Anatomy of Violence: The Biological Roots of Crime.
Crime, like most things, is partly heritable. Identical twins are more likely than fraternal twins to engage in antisocial activities.
about half of the variability in antisocial behaviour between individuals has a genetic basis. Even identical twins brought up separately show a shared tendency towards criminal behaviour.
Some specific genes have been linked to violence, like the “warrior gene”, MAOA.
Several physiological conditions are also associated with crime, including:
- A less developed prefrontal cortex:
[Raine] led the first study to image the brains of convicted murderers. Using PET scans, he found that their brains showed reduced activity in the prefrontal cortex, the region just behind the forehead that controls impulses and is responsible for planning. In other words, the murderers were less able than average to restrain themselves in stressful situations….Raine scanned the brains of people diagnosed with antisocial personality disorder, he found that their prefrontal cortexes had 11 per cent less grey matter than those of individuals who did not have the condition.
- Hormone levels:
testosterone levels in the womb can alter the size of the prefrontal cortex – it is smaller in males, which may be part of the reason most violent crimes are committed by men.
- Impaired nervous system:
Many offenders also have impairments in their autonomic nervous system, the system responsible for the edgy, nervous feeling that can come with emotional arousal. This leads to a fearless, risk-taking personality, perhaps to compensate for chronic under-arousal.
- Low heart rate. Heart rate is a good predictor of criminal tendencies. Unabomber, Ted Kaczynski, had very low resting heart rate.
Bob Holmes, “Time to get tough on the physiological causes of crime” New Scientist