The brains of people who undertake serious or sexual crimes seem to differ in a number of ways

A new study from Yale University used MRI scans to compare the brains of pedophiles and those convicted of non-sexual crimes. Paedophiles had significantly less of a substance called "white matter" that connects six areas of the brain known to play a role in sexual arousal. The researchers' theory was that the lack of adequate wiring between these centres resulted in pedophiles being unable to differentiate between appropriate and inappropriate sexual objects. New brain scanning called Pet (positron emission tomography) also allows the activity of the brain to be examined by measuring the uptake of glucose, the "fuel" of the brain. Pet has demonstrated that a region at the front of the brain – the prefrontal cortex – functions differently in murderers. This area normally controls the behavior that makes us "civilized" – self-control, maturity, judgment, tactfulness and reasoning. Violent crimes have also been associated with less specific abnormalities in the frontal lobe. Hormones are chemical messengers that travel in the bloodstream. Studies show many females imprisoned for aggressive criminal acts commit their crimes during the premenstrual phase of their menstrual cycle. This suggests that fluctuations in female sex hormones levels may regulate impulsive behavior. Further, recent research demonstrated that male adolescents with severe anti-social behavior don't produce as much of the stress hormone cortisol in response to high-tension situations. Fairchild and colleagues, publishing in the journal Biological Psychiatry in November 2008, speculate this may lead to less caution and more anger and impulsiveness during times of stress.