Aggression is behavior, verbal or physical, intended to physically hurt or harm in some other way another person or thing. Whether aggression is manifested by individuals or groups (including nations), it is the most destructive force in social relations and consequently an important social issue. A major concern in either individual or group aggression is its origin.
  • Biology has a role in aggression. Genetic influences play a major part in some aggression, as evidenced in animals specifically bred to exhibit such behavior. Studies of identical twins have frequently shown that if one twin exhibits aggressive behavior, the other often does so as well. Aggression may also have a neural basis; aggressive behavior has been produced in animals through electrical stimulation of parts of the brain.

  • Konrad Lorenz, an ethologist, proposed that aggression arises from instincts and that such instincts help members of a species maximize the use of food, space, and other resources. Other biologists have studied the aggression produced by exposing the nervous system to chemicals (drugs, such as alcohol) or hormones (such as testosterone).

  • Learning theorists such as John Dollard have suggested that frustration of goal‐directed behavior leads to aggression (the frustration‐aggression hypothesis). Imagine your response, for example, if after you've stood in line for hours to get game tickets, the person just ahead of you gets the last ones.

  • Social learning, acquisition of behaviors by watching others, is believed to function in learning aggressive behaviors. Research has shown that children model aggressive behavior, and data exist that suggest that exposure to media violence increases a person's tendency to be aggressive. Domestic violence (in which a person is beaten by her or his spouse) is a serious modern social problem. Studies indicate that male abusers often come from families in which the mother was abused or have frequently observed other violence.