Prejudice is an unjustifiable, usually negative, attitude toward a group and its members. Prejudice’s three components are beliefs (often stereotypes), emotions, and predispositions to action (discrimination). Overt prejudice in North America has decreased over time, but implicit prejudice—an automatic, unthinking attitude—continues.
     The social roots of prejudice include social inequalities and divisions. Higher-status groups often justify their privileged position with the just-world phenomenon. We tend to favor our own group (ingroup bias) as we divide ourselves into “us” (the ingroup) and “them” (the outgroup).
     Prejudice can also be a tool for protecting our emotional well-being, as when we focus our anger by blaming events on a scapegoat.

The cognitive roots of prejudice grow from our natural ways of processing information: forming categories, remembering vivid cases, and believing that the world is just and that our own and our culture’s ways of doing things are the right ways.

In psychology’s more specific meaning, aggression is any act intended to harm someone physically or emotionally. Biology influences our threshold for aggressive behaviors at three levels: genetic (inherited traits), neural (activity in key brain areas), and biochemical (such as alcohol or excess testosterone in the bloodstream). Aggression is a complex behavior resulting from the interaction of biology and experience.

Frustration (frustration-aggression principle), previous reinforcement for aggressive behavior, observing an aggressive role model, and poor self-control can all contribute to aggression. Media portrayals of violence provide social scripts that children learn to follow. Viewing sexual violence contributes to greater aggression toward women. Playing violent video games increases aggressive thoughts, emotions, and behaviors.