Half of sexual abusers of children have damage to the right temporal lobe of the brain, and 40% of sadistic rapists have similar damage to their left temporal lobe, according to psychiatrist Ron Langevin of the Clarke Institute of Psychiatry in Canada.
The temporal lobes are the portion of the brain that mediates actions from conception to execution, including the assessment of potential consequences. In effect, Langevin said, they control the more primitive instincts of the central nervous system.
Langevin performed computed tomography scanning and electroencephalography, as well as conventional psychiatric assessment on more than 400 sexual aggressors to reach his conclusion. He speculated that the damage was due to trauma before or shortly after birth, but cautioned that interpretation of the results is difficult because as many as half of the men he studied also abuse alcohol or drugs.