On 20 April 1999, at around 11:20 a.m. local time, two students wearing black trenchcoats walked into Columbine High School in Littleton, Colorado. Eric Harris, eighteen, and Dylan Klebold, seventeen, were armed with semiautomatic handguns, shotguns and explosives. They killed twelve students, one teacher, and then themselves.

On 1 December 1997, Michael Carneal killed three students at Heath High School in West Paducah, Kentucky.

On 30 April 1999 a fourteen-year-old Canadian boy walked into the W.R. Myers High School in Taber, a quiet farming community of 7,200 people two hours southeast of Calgary, Alberta. He shot and killed one seventeen-year-old...

The purpose of this review was to find out what the scientific research has discovered. I did not want to rely on what anyone else had said about it, because too many people have been basing their beliefs on what others have reported. I also did not want anyone else to have to rely on what I said. So my plan was to make the review totally transparent. Anyone reading the review would be able to see how I evaluated each study, what criticisms I offered about it, what decisions I made about what the results showed, and why I...

The first question to be asked is whether exposure to violent media and aggression are related. Are children who watch more violent programs more aggressive than those who watch fewer? This is the first question because only if the answer is yes is there much reason to pursue the issue further. If, in the real world, there is an association between exposure to violent media and aggression, this raises the possibility that the former causes the latter. If there is no such association – if children who are exposed to lots of violent programs are no more aggressive than those...

The scientific experiment is a marvellous device. Unlike other methods of inquiry, an experiment can tell you with great certainty that an action caused something to happen. As discussed in the previous chapter, when two factors or two events tend to go together, we often assume that one causes the other. People who eat carrots are less likely to have heart attacks than those who do not, so we assume that carrots prevent heart attacks. Someone tends to get migraines in warm weather, so assumes that the heat causes the headaches. Children who watch a lot of media violence tend...

Experiments conducted in psychology laboratories have various weaknesses, which I have already discussed. Though there is disagreement about the importance of these problems, I believe there is general agreement about the value of experiments done in more natural settings, sometimes called field experiments. It should be noted that the distinction between laboratory and ‘field’ is somewhat arbitrary. My own feeling is that to qualify as a field experiment, the research should be more natural than lab research in as many ways as possible. Showing films in class or in the cottages where the subjects live is quite natural; taking them...

Longitudinal research is one of the most important and revealing methods of investigating the effects of viewing media violence. With the exception of the survey studies, the goal of all of the research we have been reviewing is to test the hypothesis that exposure to violent media causes aggression. The ideal method of demonstrating causality is the experiment. However, as we have seen, the experimental work has serious limitations. The laboratory experiments are short-term, involve brief exposures, use measures that are often questionable, and are conducted in the artificial environment of the laboratory They are also prone to problems such...

Those who believe that exposure to media violence is harmful often decry the existence of television. They argue that if only there were no television at all, children would be less aggressive and the crime rate would be lower. (There would still be violence in films, but presumably the level of exposure would be much less.) I think this is rather foolish, since there was lots of aggression and crime before television and there is no evidence that children are generally more aggressive now than they were then. Nevertheless, if the causal hypothesis is correct – if television violence really...

I have discussed many different kinds of research that have attempted to gather evidence on whether exposure to media violence causes aggression. Every method has provided some interesting and useful information. Yet despite the wide variety of methods, it seems it is always possible for ingenious people to find other approaches to the problem. This section describes these other approaches that do not fit neatly into the more usual categories of research.

It is difficult to know how to classify this study. In one sense it is simply another survey that obtained information on exposure to media, measures of aggression,...

Most of the research on the effects of exposure to violent media has focused on the possibility that it causes aggression or crime. A somewhat different but related idea, which I shall call the desensitization hypothesis, is that exposure to media violence causes people to become callous or indifferent to violence. The notion is that seeing acts of violence on television or in the movies makes them seem common-place. Someone who has not seen violence in the media will presumably be shocked and upset at witnessing an act of violence. In contrast, so the argument goes, someone who has seen...

This review has considered in detail a great deal of research on the effects of exposure to media violence. Each study was described, analyzed, criticized, and evaluated. The previous sections summarized the results of each type of research. Several conclusions seem to be warranted.

First, the survey research, combined with the longitudinal studies, provides fairly good evidence that exposure to media violence – or perhaps only preference for more violent programs – is related to aggressiveness. Those who are exposed to more violence in the media and/or who prefer more violence in the media tend to be more aggressive than...