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Biology 103
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Biology and Aggression

Christy Cox

Some people claim that the United States is the most violent nation in the world (1). We are less directly involved in war than many nations, but there is an undeniable presence of violence in everyday American society. It shows up in movies, music, media, and even children's toys. And while violence on television and the radio might not be 'real' violence, many people believe that it reinforces real behavior patterns, and especially influences young children. However, not every child who watched Power Rangers on TV reenacted that violence on other children. Obviously, the formula is not that simple. But what are the multiple factors influencing violent behavior? And is that a pertinent or maybe even a dangerous question in terms of preventing or responding to violent crime? The purpose of this web paper is to explore these questions.

Inevitably, the question of influences on behavior takes us back to the ever-present debate of nature vs. nurture. Environmental influences definitely play a hugely significant part in determining whether an individual will act out aggressively (1). High stress environments can cause individuals to act out with high amounts of aggression. An environment with a high presence of violent and aggressive behavior not only creates these high levels of stress, but also reinforces violence as an acceptable social behavior. Thus there is an undeniable 'cycle of violence.' But environment is not a full proof predictor of behavior.

No self-respecting scientist-not even among those who advocate biological influences on violent behavior-believes that there is a gene coded specifically for violence that will someday be identified and treated. However, some studies have indicated that certain individuals come into the world predisposed to developing a violent or aggressive behavior pattern. These focus on physiological or chemical differences among individuals who commit acts of violence, as well as physical brain characteristics (2).

Dr. Debra Niehoff, author of The Biology of Violence offered a description of how experiences are recorded in the brain, and patterns of behavior develop that I found particularly valuable:

"The way the brain keeps track of our experiences is through the language of chemistry. It's an organic historian. These experiences get recorded as changes in the chemistry and the hormones of the nervous system and particularly the circuitry for emotion and our responses to stress. When we come to a new interaction with a new person, we bring to that a neuro-chemical profile that is based on answers to some very important questions we've answered over a period of years: Is the world safe? Are people generally trustworthy? What do I know about this person from looking at her/him? What might I know from other sources. That sets off some emotional reactions within us and that emotion, the chemistry of those feelings, is translated into our responses. Then that person reacts to us, and our emotional response to their reaction also changes brain chemistry a little bit. So after every interaction, we update our neuro-chemical profile of the world and of that relationship (3)."

Dr. Niehoff's account lends insight into the question of the interaction between nature and environment. Behavior is determined completely by environment as well as completely by biology. The two are inextricable, and actually affect each other.

Certain brain chemicals have been linked to aggressive behavior, such as testosterone and serotonin. Just as aggression is a natural part of human behavior, enabling us to play sports and achieve higher job positions through competition, both testosterone and serotonin are present in every person. However, unhealthy amounts of violence have been linked with high amounts of testosterone as well as low levels of serotonin.

Because males are viewed as naturally having more aggressive behavior patterns than females-they are ten times more likely to commit a violent crime-it makes sense that one would link the male hormone testosterone to aggressive behavior. However, there is some debate on this. Psychologists' studies have indicated that people have different expectations of male children, which may influence the way they develop. For example, when shown a videotape of a child reacting to a toy, adult viewers attribute different emotional responses depending on whether they think that child is male or female. If they were told the child was a boy, they said he was angry; if they thought it was a girl, they said she reacted out of fear (4). Other studies have indicated that men with higher levels of testosterone are more likely to exhibit violent behavior.

The serotonin link is also criticized. In 1992, a planned conference on the relationship between biology and violence was cancelled when administrator Frederick Goodwin made an impromptu speech that compared inner city youth violence to that of jungle monkeys. However, some of the most valuable research regarding serotonin's influence on behavior involves monkeys. A study at the National Institute of Health by Steve Suomin indicated that, in a well-developed society, a small number of monkeys born with low serotonin levels never develop the necessary social skills to remain in the society. These individuals are expelled from the troupe, which decreases their likelihood of survival. Additionally, Suomin found that monkeys born with normal serotonin levels could be made aggressive through neglectful or abusive up bringing. These monkeys eventually developed low serotonin as well as tendencies toward aggressive behavior. Also, a study of children with disruptive behavior disorders done by Markus Kruesi of the University of Illinois revealed low serotonin levels as a predictor of aggression (5).

Suomin's study seems an important one, because it demonstrated that biology could be changed by the environment. Monkeys born with normal levels of serotonin could develop a deficiency if they experience unhealthy interactions with their environment. Unfortunately, the study did not mention any monkeys born with low serotonin levels that were able to develop higher levels through positive societal interactions. If such a thing could be found to be possible, I think that would offer a lot of hope for children who are believed to be "predisposed" toward violence.

There are also some physical traits that have been linked to aggressive behavior. The prefrontal cortex of the brain is commonly focused on (6). The most famous example of the brain's importance to aggressive behavior is that of Phineas Gage. In 1848 he received damage to the frontal part of his brain, completely altering his personality from "intelligent and respectful" to "fitful, impulsive, and rude." Since then, many other ties have been made between that area of the brain and an inability to restrain negative behavior. Some scientists postulate that this area of the brain functions to suppress impulse behavior, including violence (7). (As a crude example: while many people may impulsively make death threats they later regret, someone with a damaged or otherwise unusual prefrontal cortex might actually act on that impulse.)

A research team from the University of Southern California studied 21 men diagnosed with Antisocial Personality Disorder, which is "characterized by irresponsibility, deceitfulness, impulsiveness, irritability, lack of emotional depth, lack of remorse, and life-long antisocial behavior." All of the men had committed violent crimes. Through brain-imaging techniques, the scientists discovered that the men had from 11 to 14 percent reduced volume of nerve cells in the prefrontal cortex than found in "normal males." (7) All of this further strengthens the link between brain composition and behavior.

However, what does it all mean concerning how violence should be viewed by society and responded too. Many people have protested research into the "biology of violence" because they are fearful of the policies that will grow out of that approach (2). Does it really matter whether an individual is biologically predisposed to aggression, in light of the knowledge that environmental factors are just as important; that the two are actually linked to the point that changing the environment can alter biology? It is much more difficult, and less ethically straightforward to attempt to change someone's physiology. However, because society is already part of an individual's environment, that is something that can be much more easily addressed. (Although social change is certainly not easy.)

I think that these concerns are valid. Research on biological determinants of violence cannot really be stopped, nor should it necessarily be. However, it should not affect policy decisions concerning the prevention of crime. Suggestions that inner city youth should be screened for biological predisposition toward crime or violence and then treated accordingly are scary for a number of reasons. They bring up issues of race, and questions regarding whether telling a child he is "predisposed" to violence is not likely to negatively influence his behavior in itself. Rather emphasis should be put on creating an environment for children that is healthy, so that the chemical process described by Dr. Niehoff will be a positive one, reinforcing healthy patterns of behavior.

WWW Sources

1. 1) The Black Collegian Online , "Campus Hate Crimes: Fruit on the American Tree of Violence"

2) Science Friday , audio discussion: "Biology of Aggression"

3) EQ Today , "The Biology of Violence, an interview with Debra Niehoff"

4)About Gender , Social Learning Theory

5) Columbia University research page , Special: Violence as a Biomedical Problem

6 Society for Neuroscience , "Violent Brains"

7 Science Daily , "Size of Brain Linked to Violence"

Continuing conversation
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10/21/2005, from a Reader on the Web

Thanks for this space.I think the biology of violence desrves continuous research and the findings should influence policy because society can never adequately repay or redress individuals victims who bear the consequences of violence -the damage, disability or death.So far our measures to curb violence have not been 100% successful and violent people continue to emerge and cause atrocities. I think for the sake of the victims it is necessary to pre-empt violence by treating all potential violent people,if only that will curtail any future harm that they may inflict on others. The world continues to witness and to my mind even condone violence perpetrated against females and children by men. is it not time to take the biological aspect of violence more seriously and examined the men who may be potentially at risk so that something can be done to release them from their own nature?




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