Aggression is usually defined by behavioral scientists as behavior that is intended to harm another person. Common forms of aggression are physical (for example, punching), verbal (for example, saying or writing hurtful things to another person), and relational (for example, intentionally and publicly not inviting someone to a party to harm his social relationships). Violence usually is conceived as more extreme forms of physical aggression that are likely to result in physical injury. The most extreme form of violence is homicide, but any form of aggressive behavior that is likely to result in an injury serious enough to warrant medical attention is considered violence. Thus, fights involving weapons as well as fistfights by adolescents old enough to be able to inflict serious injuries are considered acts of violence.
The relation of these terms to violent “crime” requires some comment. The vast majority of media violence research focuses on aggressive and violent behavior as defined earlier. Violent crime is a much more restrictive category and is applied only in cases where someone has been arrested for a crime classified by police as a major crime against persons, such as murder, rape, and assault. There are at least two reasons for the discrepancy between the behavioral scientists' focus and the criminologists' focus. First, the criminological focus is based more heavily on the consequences of a specific action, whereas the behavioral science focus is almost exclusively based on the intention behind the action. Understanding the causes of violent behavior requires this focus on intentions rather than on whether the person succeeded in harming the individual and was subsequently caught. Second, not only is it much more difficult and expensive to do research on violent crime because it is relatively rare (thereby requiring huge sample sizes), but also certain types of research, such as experimental studies, would be