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Biology 202
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The Nature of Aggression (or is it Nurture?)

Sarah McCawley

Every night on the news there are reports about murders, wars, and rapes. But the news isn't the only place where people encounter violent or aggressive behavior. Driving home from work, people get cut off and cussed at on a daily basis. At school, children fight over who will be the first in the lunch line. On the street, people get pushed out of the way if they are not walking fast enough. The list could go on and on and on. The point is that humans exhibit aggressive behavior on a regular basis. However, does anyone know why people display these behaviors? Why do certain people seem more aggressive? Is there just one thing that controls when and how aggressive someone becomes? These are all questions that researchers have been addressing for many years. In fact there has been quite a debate over what causes people to be aggressive. However, in order to try to understand where aggression may stem from, you must understand how aggression is defined as well as all of the possibilities that may cause it.

Aggression is an action. It is intended to harm someone. It can be a verbal attack--insults, threats, sarcasm, or attributing nasty motives to them--or a physical punishment or restriction (1). Aggression also seems to be a way of maintaining social order among many species. Animals compete with each other over food, mates, and dwelling spaces, often showing aggression and occurring among virtually all vertebrate species, including humans. However, if aggression is an effective way of maintaining social order, reckless violence appears to be a poor survival mechanism. Nevertheless, this trait has not been wiped out. Since it hasn't disappeared, it is logical that researchers have tried to understand the nature of this behavior. In doing this, there has been an ongoing argument of what its source is.

The nature vs. nurture topic has been a continuing debate for many aspects of human behavior, including aggression. There have been many studies indicating that chemical relationships between serotonin, testosterone, and frontal lobe brain chemistry may play a key role in determining aggressive behavior, while other studies have explored environmental and societal factors that have been said to control patterns in human aggression.

The argument for nature surrounds the possible biological reasons for why human aggression is exhibited. The reasons for why there is aggressive behavior in humans include a range of hypotheses. Aggression may have a chemical, hormonal, or genetic basis. Research has shown that stimulation of certain parts of animals' brains leads to aggression. Stimulation of other parts stops aggression (1). Some researches believe that it stems from low levels of serotonin. Terrie Moffitt and colleagues studied the blood serotonin levels of 781 21-year-old men and women. The researchers report that "in this study, elevated whole blood serotonin was characteristic of violent men." (Low brain levels of serotonin, but high levels of blood serotonin, are associated with behavior disorders-apparently because of serotonin's different origin and function in blood and brain.) The violent men's mean serotonin level was .48 standard deviations (SD) above the norm for males as a group, and .56 SD above the mean for non-violent men. Among female subjects, no relationship between serotonin levels and aggression was seen (6). Others seem to think that it may be due to testosterone. High testosterone (male sex hormone) is associated with more unfaithfulness, more sex, more divorce, more competitiveness, and anti-social behavior (1). And still others believe that it may stem from a specific gene. A large survey of adopted children has found that living with an adoptive parent who committed crimes is less risky than merely having the genes from a person who committed crimes (1).

The argument for nurture involves aspects of human life that surround societal reasons for why aggression occurs as a part of human behavior. Certain aspects of human life have been singled out as factors that seem to contribute to the development and control of aggression, including cognitive factors, family factors, neighborhood factors, and peer influences.

The Frustration-Aggression Hypothesis model states simply that: "Aggression is always a consequence of frustration." and "The existence of frustration always leads to some form of aggression", where Frustration is blocking a path towards the goal and Aggression is a series of actions whose goal response is injury to another organism or its substitute (2). When a human being notices that his way to a goal is blocked, aggression arises. Here aggression arises because the person is frustrated (3). Unfortunately, the second part of this sweeping claim is patently false. Frustration may make you bite your tongue, think about something else, or laugh it off. Heavily influenced by behaviorism as well as by Freud, frustration-aggression theorists define frustration as the thwarting of an action that would have produced reward or gratification (5).

The Social Learning Theory denies that humans are innately aggressive and that frustration automatically leads to aggression. Instead Bandura (1973) argues that aggression is learned in two basic ways: (1) from observing aggressive models and (2) from receiving and/or expecting payoffs following aggression. The payoffs may be in the form of (a) stopping aggression by others, (b) getting praise or status or some other goal by being aggressive, (c) getting self-reinforcement and private praise, and (d) reducing tension (1).

Both of the above theories seem to rely strictly on factors the fall under the nurture category and the first part of the paper explains the factors that could back the nature side of the debate. However, there are still other theories that do not fall strictly into either of these categories. Freud's Instinct Theory describes something that is innate, but does not give a concrete source for the aggression. The assumption behind this theory is that two primitive forces, the life and death instincts, oppose each other in our subconscious, and this incongruence is the origin of all desires to aggress. Freud asserted that this was a process void of thought patterns, and driven solely and entirely by our instincts - the aim being satisfaction. According to this theory, aggression was the main representative of the death instinct (2). In this theory, it appears that it could biological, because it is supposed to be instinctual, but what is it an instinct for?

According to Lorenz' Hydraulic Model of Motivation, the degree of consummatory response is a function of the amount of accumulated action specific energy and the sign stimuli to which the animal is exposed. Action specific energy accumulates in a reservoir until released by the appropriate stimulus, represented by weights on a scale pan, or until the pressure on the valve causes an action pattern to occur spontaneously (vacuum activity). The consummatory response or fixed action pattern(s) released vary depending upon how much action specific energy is released from the valve. Hydraulic Theory predicts that aggression is inevitable - the accumulating energy must find an outlet, humans and animals will actively 'look for fights', after an attack an animal / human will become less aggressive, and animals reared in isolation will show aggressive behavior (4). This model requires something to trigger the aggressive behavior, but like Freud, appears to somehow be innate in that it the aggression is inevitable.

From all of the possibilities explored and the theories made, you might think that there has been a conclusion made about exactly where aggression originates as well as what could incite a particular aggressive action, but there has not been. No one knows what causes aggression or if it can even be said that there is one thing that causes it. Although this may not seem like a satisfying answer to the questions posed at the start of the paper, it is more satisfying than it appears. Out of everything that I have learned this semester, one of the most important things is that there are multiple ways to answer a question and often it is a combination of answers that are needed to form an accurate conclusion. And even when there seems to be an accurate answer, there is always a possibility that it can be wrong. That is why researchers continue to question those things that surround them. So, although, there may not be one conclusive answer to why people are aggressive, it doesn't mean that a combination of theories can't be right or that someday, researchers will find the answer.

WWW Sources

1) ANGER AND AGGRESSION , Psychological Self-Help Chapter 7



4) University of Plymouth Department of Psychology PSY124 Integrative Topics in Psychology: Aggression

5) Features of American Drinking and Violence , WAGUESPACK SEMINARS AND WORKSHOPS


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