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Any act that is intended to cause pain, suffering, or damage to another person.

Aggressive behavior is often used to claim status, precedent, or access to an object or territory. While aggression is primarily thought of as physical, verbal attacks aimed at causing psychological harm also constitute aggression. In addition, fantasies involving hurting others can also be considered aggressive. The key component in aggression is that it is deliberate—accidental injuries are not forms of aggression.

Theories about the nature and causes of aggression vary widely in their emphases. Those with a biological orientation are based on the idea that aggression is an innate human instinct or drive. Sigmund Freud explained aggression in terms of a death wish or instinct (Thanatos) that is turned outward toward others in a process called displacement. Aggressive impulses that are not channeled toward a specific person or group may be expressed indirectly through safe, socially acceptable activities such as sports, a process referred to in psychoanalytic theory as catharsis. Biological theories of aggression have also been advanced by ethologists, researchers who study the behavior of animals in their natural environments. Several have advanced views about aggression in humans based on their observations of animal behavior. The view of aggression as an innate instinct common to both humans and animals was popularized in three widely read books of the 1960s—On Aggression by Konrad Lorenz, The Territorial Imperative by Robert Ardrey, and The Naked Ape by Desmond Morris. Like Freud's Thanatos, the aggressive instinct postulated by these authors builds up spontaneously—with or without outside provocation— until it is likely to be discharged with minimal or no provocation from outside stimuli.

Today, instinct theories of aggression are largely discredited in favor of other explanations. One is the frustration-aggression hypothesis first set forth in the 1930s by John Dollard, Neal Miller, and several colleagues. This theory proposes that aggression, rather than occurring spontaneously for no reason, is a response to the frustration of some goal-directed behavior by an outside source. Goals may include such basic needs as food, water, sleep, sex, love, and recognition. Contributions to frustration-aggression research in the 1960s by Leonard Berkowitz further established that an environmental stimulus must produce not just frustration but anger in order for aggression to follow, and that the anger can be the result of stimuli other than frustrating situations (such as verbal abuse).

In contrast to instinct theories, social learning theory focuses on aggression as a learned behavior. This approach stresses the roles that social influences, such as models and reinforcement, play in the acquisition of aggressive behavior. The work of Albert Bandura, a prominent researcher in the area of social learning, has demonstrated that aggressive behavior is learned through a combination of modeling and reinforcement. Children are influenced by observing aggressive behavior in their parents and peers, and in cultural forms such as movies, television, and comic books. While research has shown that the behavior of live models has a more powerful effect than that of characters on screen, film and television are still pervasive influences on behavior. Quantitative studies have found that network television averages 10 violent acts per hour, while on-screen deaths in movies such as Robocop and Die Hard range from 80 to 264. Some have argued that this type of violence does not cause violence in society and may even have a beneficial cathartic effect. However, correlations have been found between the viewing of violence and increased interpersonal aggression, both in childhood and, later, in adolescence. In addition to its modeling function, viewing violence can elicit aggressive behavior by increasing the viewer's arousal, desensitizing viewers to violence, reducing restraints on aggressive behavior, and distorting views about conflict resolution.

As Bandura's research demonstrates, what is crucial in the modeling of violence—both live and on screen—is seeing not only that aggressive behavior occurs, but also that it works. If the violent parent, playmate, or superhero is rewarded rather than punished for violent behavior, that behavior is much more likely to serve as a positive model: a child will more readily imitate a model who is being rewarded for an act than one who is being punished. In this way, the child can learn without actually being rewarded or punished himself—a concept known as vicarious learning.

The findings of social learning theory address not only the acquisition, but also the instigation, of aggression. Once one has learned aggressive behavior, what environmental circumstances will activate it? The most obvious are adverse events, including not only frustration of desires but also verbal and physical assaults. Modeling, which is important in the learning of aggression, can play a role in instigating it as well. Seeing other people act in an aggressive manner, especially if they are not punished for it, can remove inhibitions against acting aggressively oneself. If the modeled behavior is rewarded, the reward can act vicariously as an incentive for aggression in the observer. In addition, modeled aggression may serve as a source of emotional arousal.

Some aggression is motivated by reward: aggressive behavior can be a means of obtaining what one wants. Another motive for aggression is, paradoxically, obedience. People have committed many violent acts at the bidding of another, in both military and civilian life. Other possible motivating factors include stressors in one's physical environment, such as crowding, noise, and temperature, and the delusions resulting from mental illness. In addition to the acquisition and instigation of aggression, various types of reinforcement, both direct and vicarious, help determine whether aggression is maintained or discontinued.

Researchers have attempted to learn whether certain childhood characteristics are predictors of aggression in adults. Traits found to have connections with aggressive behavior in adulthood include maternal deprivation, lack of identification with one's father, pyromania, cruelty to animals, and parental abuse. A 22-year longitudinal study found patterns of aggression to be established by the age of eight—the aggressive behavior of both boys and girls at this age was a strong predictor of their future aggression as adults. Other factors cited in the same study include the father's upward social mobility, the child's degree of identification with parents, and preference for violent television programs.

Further Reading

Aggression and Peacefulness in Humans and Other Primates. New York: Oxford University Press, 1992.

Aggressive Behavior: Current Perspectives. New York: Plenum Press, 1994.

Bandura, Albert. Aggression: A Social Learning Analysis. New York: Prentice-Hall, 1973.

Of Mice and Women: Aspects of Female Aggression. New York: Academic Press, 1992.

Additional topics

Psychology EncyclopediaPsychological Dictionary: Abacus to Courage