Modern research has taught us a good deal about the neurobiology of antisocial traits. It is important, however, to distinguish the neurobiological traits associated with impulsivity and those associated with psychopathy, as they may be quite different. We know that people with high levels of impulsivity and impulsive aggression have less 0 activation in their orbital frontal region. This part of the frontal lobe lies just above the eye sockets and is associated with behavioral control. Some researchers suggest that the orbital frontal cortex links planned behavior with memories of punishment. In other words, the person is more likely to reason, “Oh oh, if I hit this person, I might get hit back.” When the orbital frontal cortex is compromised, the fear of punishment is not strong enough to deter the person from impulsive and reckless actions.

There is also evidence of decreased function in the dorsolateral frontal cortex in impulsive aggression. This area is involved in abstract and complex thought, abilities that are often compromised in impulsive-aggressive people. The serotonin system may also be abnormal in impulsive people. The neurotransmitter serotonin also seems to be involved in behavioral control. People with hyperactive serotonin systems may have over-controlled behavior, while the opposite appears to be true with impulsive people, whose serotonin system is underactive.