This is the 2007 version. Click here for the 2017 chapter 15 table of contents.


Aggression can be defined as any behavior intended to hurt others. A person who accidentally injures someone else is not usually considered aggressive, but a person who tries to hurt somebody (even if the person fails) is considered aggressive.

What is the difference between antisocial and prosocial aggression?

While most people would assume aggression is always antisocial (literally "against society") there are both antisocial and prosocial forms of aggression. Prosocial aggression is that which upholds the rules or norms of society. A bank robber is engaged in antisocial aggression, while a police officer who arrests a bank robber is engaged in prosocial aggression.

Causes of aggression

Psychologists long believed that frustration caused aggression. In a book titled Frustration and Aggression, Dollard and colleagues at Yale stated the theory in absolute terms: "aggression is always a consequence of frustration" (Dollard, Doob, Miller, Mowrer, & Sears, 1939, p.1).

Early studies by social psychologists produced some evidence that appeared to support this theory. For example, Barker, Dembo, and Lewin (1941) showed children a room full of attractive toys. Some children were allowed to play with the toys right away. Others had to stand outside the room watching. When finally allowed inside to play with the toys, the second group engaged in more aggressive behavior such as throwing the toys around and breaking them.

What happened to the frustration aggression hypothesis?

The frustration/aggression hypothesis stimulated much research, but the results failed to confirm the theory. Yates (1962) reviewed 50 studies and found only mild support for the frustration/aggression hypothesis.

As the frustration/aggression hypothesis fell out of favor, some psychologists proposed that pain caused aggression. Again, animal studies did not provide very good support for the theory. In most cases, when animals experienced pain, they showed mostly defensive reactions rather than aggression.

What does produce aggression?

So, what actually produces aggression? In primate societies of all different types, status-seeking leads to aggression. Animals are aggressive to others in order to dominate them, ward of romantic rivals, and keep a high position in a group hierarchy.

In humans, a predominant influence is observational learning : seeing aggressive behavior acted out in families or on TV. The most famous study showing the effects of observational learning on aggression is the Bobo doll research of Bandura, Ross, and Ross (1961). A Bobo doll is an inflatable doll with a weight such as sand in the bottom, so each time it is knocked down, it pops right back up. It invites aggression (hitting) from small children. (These toys are almost never called Bobo dolls in toy stores, but they were in this study.) Bandura, Ross, and Ross arranged for nursery school children to watch an adult spend nine out of ten minutes in aggressive play with a five foot Bobo doll. The adult first assembled some toys, then turned his attention to the Bobo doll. He knocked it down, kicked it into the air, made angry comments toward it, and hit it with a mallet.

What was the famous "Bobo doll" study?

Later, the children were put in a mildly frustrating situation. The children were given some of their favorite toys, and then the toys were taken away. Most researchers still believed in the frustration/aggression hypothesis at the time, so researchers thought this would increase the likelihood of aggression. After this, the children were left in a room with a three-foot Bobo doll and other toys, such as crayons, dolls, and toy bears. The researchers secretly observed for 20 minutes. The children who had witnessed the adult striking the Bobo doll were far more likely to strike their own three-foot Bobo doll. A control group (which had not seen the adult abusing the Bobo doll) was less likely to act aggressive.

In further studies, a video recording of an aggressive adult was found to be as effective as exposure to a real adult in stimulating aggressive play by children. So this research by Bandura, Ross, and Ross (1961) turned into one of the first studies suggesting a link between violence on TV and violence in real-life behavior.

Variations on the experiment showed that aggression was more likely to occur if (1) the adult model was rewarded for acting aggressive toward the doll, or (2) the adult model was the same gender as the child, and (3) if the child had a previous friendship with the adult model. Researchers also found that preschoolers already rated high in aggression were more likely to respond to a video showing aggression, and boys were more likely to be aggressive than girls.

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