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Biology 202
2002 Second Paper
On Serendip

The Brain and Violence: An Unhealthy Combination

Balpreet Bhogal

"Jack was walking down the street enjoying a snack he had just bought at a convenience store. Feeling good, he smiled at the stranger coming toward him while continuing to eat. The stranger suddenly pulled out a knife and began stabbing Jack. Bystanders pulled the knife away, but too late."

"After the killing, the attacker said that he was deeply sorry. He had sensed a strange aura, then experienced a flashback of having been bitten and of having a hernia operation under local anesthesia. That was followed by hallucinations about Jack cutting off his flesh, testicles, and heart to eat them" (6).

Everyday on the news one hears stories of crimes and murders such as the one above. Murders are committed every day; stores are robbed every hour; crimes are committed constantly. The truth is that violence has sadly become a common and prevalent occurrence in society today. In essence, one must ask himself whether or not these violent tendencies have any biological relation whatsoever. Is violence caused by disruptions or damage to the brain? Is there a genetic correlation? Or is violence brought about by something else, such as economic difficulties or social or cultural differences? And one must ask himself an even broader question-whether a cause for violence even exists.

In 1848, a railroad worker, Phineas Gage, was working when an explosion caused an iron rod to impale his skull, damaging the front part of his brain. Although Gage miraculously survived, his behavior severely changed in that the intelligent and respectful man everyone knew suddenly because fitful, impulsive, and rude (2).

This case is one of the first indications that violence may be related to some kind of damage or abnormality in the brain. Researchers have found correlations between violent and aggressive tendencies to damage or abnormalities to a specific part of the brain. Gage's accident probably resulted in damage to the prefrontal cortex. The prefrontal cortex is the brain's foremost outer position, located behind the eyes. This area of the brain is especially important because of it's importance in the orchestration of emotion, arousal, and attention. The prefrontal cortex seems to be the part of the brain that enables people to restrain themselves from acting on all of their impulses and is extremely vital for a child's ability to learn to feel remorse, conscience, and social sensitivity (5).

However, although the function of the prefrontal cortex is known, why, or how, would prefrontal deficits cause violent tendencies or a more aggressive character? Adrian Raine, a psychopathologist from USC suggests that damage or abnormalities of the prefrontal cortex may result in a condition known as Antisocial Personality Disorder, or APD. This disorder is characterized by irresponsibility, deceitfulness, impulsiveness, lack of emotional depth and antisocial behavior. Raine, in his study, suggested three reasons why prefrontal deficits may cause such a personality (5). Firstly, the prefrontal cortex is responsible for self-restraint and deliberate foresight. If this part of the brain was damaged, then one effect that would arise would be the tendency for one to act on all his impulses without thinking ahead or thinking of the consequences. Second, the prefrontal cortex is important for learning conditioned responses. This area of the brain has been thought to be central to a child's ability to learn to feel remorse, conscience, and social sensitivity (7). If the prefrontal cortex was to function abnormally, how is the child supposed to learn how to have a conscience? For example, one study reported that children who received damage to their prefrontal cortex before the age of seven developed abnormal social behavior, which was characterized by their inability to control their aggression and anger (2). Lastly, Raine suggests that if prefrontal deficits underlie the APD group's low levels of autonomic arousal, these people may unconsciously be trying to compensate through stimulation-seeking (5).
There have been many studies done concerning violence and its relationship to the prefrontal cortex. In July, 2000, UW-Madison psychologist Richard Davidson analyzed brain imaging data from a large, diverse group of studies on violent subjects and those predisposed to violence to find any connections between the brain and violent tendencies. His studies focused on individuals diagnosed with APD, convicted murderers, and those with childhood brain injuries (4). He hypothesized that impulsive aggression and violence arise as a consequence of faulty emotion regulation (3).

Davidson and his colleagues found common neurological trends among many of their subjects in the brain's inability to properly regulate emotion. One core finding that Davidson's study found dealt with the interplay among several distinct regions of the brain, primarily the orbital frontal cortex, the anterior cingulate cortex, and the amygdala. They found that normal brain activity in the orbital and anterior regions were either entirely absent or slowed in many of their studies, while the amygdala showed normal or heightened activity. The inability of these two regions of the brain to counteract the response of the amygdala may explain how threatening situations can become explosive in some people with damage to the prefrontal cortex (4).

There also exist many recent studies that attempt to relate genetics to the increased tendencies for violence in some people. Although no single gene for human violence has been discovered yet, data from molecular geneticists suggest that multiple genes may interact to prime individuals to this behavior (1). Davidson's study also described a large group of subjects who had a genetic deficit that caused a disruption in the brain's seretonin levels. Seretonin has been hypothesized to hold inhibitory control over impulsive aggression. Disruption of the seretonin level may contribute to increased aggression within the individual (3).

However, although these recent studies such as Davidson's correlate genetics and prefrontal damage to increased violent tendencies, can one actually say that this is the only cause of violence? When analyzing and/or observing behavior, one automatically relates his observations to the brain; however, in stressing the function of the brain, one cannot ignore the importance of social influences on behavior (8). Adrian Raine stresses this case: "We are talking about a predisposition to antisocial behavior. Some people who have prefrontal deficits do not become antisocial, and some antisocial individuals do not have prefrontal deficits. It's important to make clear that biology is not destiny" (5). Non-biological factors such as socioeconomic and cultural influences may play a major role in violent tendencies. Issues such as unemployment, lower educational level, alcohol use, and access to firearm all contribute to violent crimes (1). Not only do biological factors need to be stressed, but so do cultural factors. Violence is found all over in movies, video games, the nightly news, professional sports and many more socially accepted types of media and entertainment. Couldn't exposure to violent events profound behavioral consequences?

Although all the above trends and relationships implied by these studies exist, do they prove that violence is ultimately caused by some type of biological disorder or social influence? By implying this, one is assuming that every man or woman who commits a crime or acts with violent tendencies does so by some type of brain damage, genetic disorder, or social problem. If anything, by believing this, society is giving people an excuse to commit crimes and act on their violent behavior; if biological or social influences ultimately cause violence, does that redeem one's actions? Does this give criminals an excuse to murder, cheat, and steal? Can their violent tendencies and criminal actions be reasoned in the court of law as being out of their hands because of damage to their prefrontal cortex when they were a child? Although these studies express a trend between brain damage to the prefrontal cortex and violence, one cannot use this to makes excuses for those who act on this aggressive behavior. A correlation between brain damage and violence might have been found, but how to act on this newfound discovery still needs to be discussed before anything else can be done.


1) Violence and Brain: An Urgent Need for Research

2) Brain Briefings: Violent Brains

3) Dysfunction in the Neural Circuitry of emotion Regulation-A Possible Prelude to Violence

4) Violent Behavior Linked To Specific Brain Dysfunction

5) Size of Brain Linked to Violence

6) Sudden Brain Seizures Said to Trigger Violence

7) Brain Size Linked to Violence

8) Mark, Vernon H. Violence and the Brain. New York: Harper & Row Publishers, 1970.

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