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Biology 202
2002 Second Paper
On Serendip

Aggression: Biological, Psychological and Cultural Explanations

Ashley Farrell

Most people will agree that aggression can become dangerous and that it is a serious problem. The source of different acts of aggression is trying to be understood from medical, psychological and cultural perspectives. Some scientists try to treat the abnormal aggressive behavior with medication, while others go deeper and try to find out why they have abnormal behavior. Some answers are biological, like genes and hormones, other answers are psychological, like rejection as a cause of aggression, and still others are cultural, blaming aggression on violence in the media.

Some men who are aggressive are being treated by scientists who are using SPECT, Single Photon Emission Computerized Tomography, to identify regions of the brain that are causing the problems with aggression. (1) SPECT creates a color picture of the blood flow and activity in the brain and variation in color reveals abnormalities and damaged regions. (1) Unusual increased or decreased activity that are key in causing aggression are often found in three areas of the brains. (1) Aggressive thoughts reside in the left temporal lobe; the anterior cingulate gyrus controls repeated thoughts and amount of attention given to something; and the prefrontal cortex controls impulse. (1) Usually aggressive men have too much or too little activity in the left temporal lobe, too much activity in the anterior cingulate gyrus and too little activity in the prefrontal cortex so that they cannot control themselves. (1) By identifying which region or regions are abnormal scientists can prescribe the best drug treatment for that specific person. Drugs help balance the activity in their brains, but why are they imbalanced in the first place?

In a few cases, faulty genes have been found to be the cause of over aggression. There is a Dutch family that has a long history of maternally linked men with aggression problems. (2) Because it is maternally passed down and only affects the men it is decidedly a problem with a recessive gene on the X chromosome. (2) After years of research there was a breakthrough that allowed them to pinpoint the defect to the MAO gene area, which consists of the genes MAOA and MAOB. (2) Both genes produce monoamine oxidase enzymes, so they measured the levels of the different enzymes to determine the specific gene. (2) Eventually a defect in the gene MAOA was found to be the cause of their abnormal aggression. (2) How does this discovery help the aggression problem so prevalent in today's society? Well, it is not clear yet whether this gene is a problem for people outside of the family who are aggressive, and generalizing could be dangerous. One scientist warns that "it would be a disaster if people suddenly decided to begin screening babies for monoamine oxidase deficiencies--as some did for the XYY defect." (2) Whatever scientists do with this new information it is another step towards answering questions about the origin of aggression.

Scientists have also been studying aggression in animals. Male mice that don't have the gene that allows nitric oxide, a neurotransmitter, to be produced in the brain are extremely physically and sexually aggressive. (3) On the other hand, when the brains of female mice were not producing nitric oxide they were remarkably not aggressive in situations where they would normally be aggressive. (4) The surprising difference has not yet been explained. Rats without gene mutations also show a difference in amount of aggression between males and females. (5) The fact that male rats are much more aggressive than females is related to the finding that male rats have depleted amounts of dopamine and serotonin in their brain compared to female rats. (5) Levels of serotonin also have a negative correlation to aggressive behavior in humans. (6) When there is more serotonin, there is less aggressive behavior. Many correlations have been found between aggression and certain chemicals in the body. One study has shown that low levels of cortisol in saliva of boys are correlated with the boys antisocial and aggressive behaviors. (7) Another study found that aggressive criminals have abnormal ratios of serum copper and plasma zinc in their blood, when compared to non-aggressive non-criminals. (8) One thing to keep in mind, however, is that correlation study findings only show associations and do not show cause and effect, so lack of serotonin could cause high aggressive behavior, or high aggressive behavior may cause low levels of serotonin.

Many times aggression in youth has been blamed on media, specifically TV and video games. One longitudinal study done by Leonard Eron and L. Rowell Heusmann found that eight year olds who watch a lot of violent TV are more likely to be arrested by the time they're thirty years old. (9) This study has been strongly disputed by Jonathan Freedman and Richard Rhodes on the basis that the numbers are not as significant as Eron and Heusmann claim. (9) Freedman and Rhodes go so far as to postulate that watching violence can be good for people. (9) Craig A. Anderson and Karen E. Dill found that the effects of video game violence exposure largely depend on whether or not an individual has an aggressive personality. (10) If one has a high aggressive personality and high exposure to video game violence, their aggressive behavior increases dramatically more than those with low aggressive personalities and high video game exposure. These results could be expected or surprising depending on the viewpoint taken, and as there is no such thing as a perfect study there are probably valid arguments against these studies. As a coping mechanism people create different scripts in their mind to deal with different problems. One concern about violent video games and TV is that the violence is presented as a solution to problems and that kids might develop scripts that use violence. (10) On the other hand playing violent video games do not cause direct harm to people, so it can be argued that playing these games are a way of releasing anger in a healthy way- much like hitting a pillow instead of one's sister.

It is thought by some people in this country that if there were less exposure and promotion of weapons, there would be less violence and aggression. One response to this is the saying 'guns don't kill people, people kill people.' But there have been many studies that show that the presence or pictures of guns make people more aggressive. (11) One recent study has explained this occurrence by showing that exposure to weapons increases aggressive thoughts. (11) When aggressive thoughts are more prominent in the brain, then people are less likely to act rationally and more likely to act on their aggressive impulse when provoked. (11) Another study focused on rejection in youths and the aggressive behavior elicited by being rejected by peers. (12) Rejection was found to be a direct cause of aggression. So, both the presence of weapons and the feeling of being rejected aid in increased, abnormal aggressive behavior.

We have begun to look at different explanations of the why's and how's of aggression. Different biological, social and psychological reasons are presented and are equally supported and rejected. One thing that can be determined by acknowledging the different possible causes of aggression is that there is not one thing that causes aggression, because everyone acts differently to different problems. Not everyone who is rejected acts out aggressively, so maybe some of the people who do act aggressively have other problems that are biological in nature. Aggression is a bio-psycho-social issue that is being addressed, and needs to be addressed in the future, from all different perspectives.


(1) Aggression

(2) Evidence found for a possible 'aggression' gene.

(3) Scientists Discover a Genetic Basis for Aggressive Behavior in Male Mice

(4) Brain Chemical Mellows Male Mice, Makes Mouse Mothers Tough

(5) Male aggression: inborn, not learned behavior

(6) Relationship between 5-HT function and impulsivity and aggression in male offenders with personality disorders

(7) Low Levels Of Salivary Cortisol Associated With Aggressive Behavior

(8) Copper, Zinc Levels Linked to Aggression

(9) Should You Let Them Watch?

(10) Video Games and Aggressive Thoughts, Feelings, and Behavior in the Laboratory and in Life

(11) Presence of Weapon Increases Aggressive Behavior

(12) If You Can't Join Them, Beat Them -- Psychologists Find Rejection Causes Aggression

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