by Craig A. Anderson, [1] Leonard Berkowitz, [2] Edward Donnerstein, [3] L. Rowell Huesmann, [4] James D. Johnson, [5] Daniel Linz, [6] Neil M. Malamuth, [7] and Ellen Wartella [8] 1 Department of Psychology, Iowa State University; 2 Department of Psychology, University of Wisconsin; 3 College of Social & Behavioral Sciences, University of Arizona; 4 Institute for Social Research, University of Michigan; 5 Department of Psychology, University of North Carolina-Wilmington; 6 Department of Communication and Law and Society Program, University of California, Santa Barbara; 7 Department of Communication/Speech, University of California, Los Angeles; and 8 College of Communication, University of Texas at Austin
Psychological Science in the Public Interest, Vol. 4, No. 3, December 2003
Copyright © 2003 American Psychological Society
NOTICE: THIS WORK MAY BE PROTECTED BY COPYRIGHT
YOU ARE REQUIRED TO READ THE COPYRIGHT NOTICE AT THIS LINK BEFORE YOU READ THE FOLLOWING WORK, THAT IS AVAILABLE SOLELY FOR PRIVATE STUDY, SCHOLARSHIP OR RESEARCH PURSUANT TO 17 U.S.C. SECTION 107 AND 108. IN THE EVENT THAT THE LIBRARY DETERMINES THAT UNLAWFUL COPYING OF THIS WORK HAS OCCURRED, THE LIBRARY HAS THE RIGHT TO BLOCK THE I.P. ADDRESS AT WHICH THE UNLAWFUL COPYING APPEARED TO HAVE OCCURRED. THANK YOU FOR RESPECTING THE RIGHTS OF COPYRIGHT OWNERS.
Address correspondence to Craig A. Anderson, Department of Psychology, W112 Lagomarcino Hall, Iowa State University, Ames, IA 50011-3180; e-mail: caa@iastate.edu.
Summary—Research on violent television and films, video games, and music reveals unequivocal evidence that media violence increases the likelihood of aggressive and violent behavior in both immediate and long-term contexts. The effects appear larger for milder than for more severe forms of aggression, but the effects on severe forms of violence are also substantial r = .13 to .32) when compared with effects of other violence risk factors or medical effects deemed important by the medical community (e.g., effect of aspirin on heart attacks). The research base is large; diverse in methods, samples, and media genres; and consistent in overall findings. The evidence is clearest within the most extensively researched domain, television and film violence. The growing body of video-game research yields essentially the same conclusions.
Short-term exposure increases the likelihood of physically and verbally aggressive behavior, aggressive thoughts, and aggressive emotions. Recent large-scale longitudinal studies provide converging evidence linking frequent exposure to violent media in childhood with aggression later in life, including physical assaults and spouse abuse. Because extremely violent criminal behaviors (e.g., forcible rape, aggravated assault, homicide) are rare, new longitudinal studies with larger samples are needed to estimate accurately how much habitual childhood exposure to media violence increases the risk for extreme violence.
Well-supported theory delineates why and when exposure to media violence increases aggression and violence. Media violence produces short-term increases by priming existing aggressive scripts and cognitions, increasing physiological arousal, and triggering an automatic tendency to imitate observed behaviors. Media violence produces long-term effects via several types of learning processes leading to the acquisition of lasting (and automatically accessible) aggressive scripts, interpretational schemas, and aggression-supporting beliefs about social behavior, and by reducing individuals’ normal negative emotional responses to violence (i.e., desensitization).
Certain characteristics of viewers (e.g., identification with aggressive characters), social environments (e.g., parental influences), and media content (e.g., attractiveness of the perpetrator) can influence the degree to which media violence affects aggression, but there are some inconsistencies in research results. This research also suggests some avenues for preventive intervention (e.g., parental supervision, interpretation, and control of children’s media use). However, extant research on moderators suggests that no one is wholly immune to the effects of media violence.
Recent surveys reveal an extensive presence of violence in modern media. Furthermore, many children and youth spend an inordinate amount of time consuming violent media. Although it is clear that reducing exposure to media violence will reduce aggression and violence, it is less clear what sorts of interventions will produce a reduction in exposure. The sparse research literature suggests that counterattitudinal and parental-mediation interventions are likely to yield beneficial effects, but that media literacy interventions by themselves are unsuccessful.
Though the scientific debate over whether media violence increases aggression and violence is essentially over, several critical tasks remain. Additional laboratory and field studies are needed for a better understanding of underlying psychological processes, which eventually should lead to more effective interventions. Large-scale longitudinal studies would help specify the magnitude of media-violence effects on the most severe types of violence. Meeting the larger societal challenge of providing children and youth with a much healthier media diet may prove to be more difficult and costly, especially if the scientific, news, public policy, and entertainment communities fail to educate the general public about the real risks of media-violence exposure to children and youth.
***
For more than five decades, Americans have been concerned about the frequent depiction of violence in the mass media and the harm these portrayals might do to youth. Reflecting this concern, several major United States Government investigations and reports have examined the research on the association between youthful media consumers’ exposure to television violence and their aggressive behavior—the 1954 Kefauver hearings, the 1969 National Commission on the Causes and Prevention of Violence, the 1972 Surgeon General’s report Television and Growing Up (U.S. Surgeon General’s Scientific Advisory Committee, 1972), and the 1982 National Institute of Mental Health (NIMH) report Television and Behavior. In 1972, U.S. Surgeon General Jesse Steinfeld testified before Congress that “the overwhelming consensus and the unanimous Scientific Advisory Committee’s report indicates that televised violence, indeed, does have an adverse effect on certain members of our society” (Steinfeld, 1972, p. 26). The 1982 NIMH report reinforced this conclusion, and professional organizations took a similar position in viewing media violence as a serious threat to public health because it stimulates violent behavior by youth. By the early 1990s, most researchers in the field had arrived at a consensus that the effect of media violence on aggressive and violent behavior was real, causal, and significant.
A number of professional groups have also addressed the state of relevant research on media violence (e.g., Eron, Gentry, & Schlegel’s, 1994, report for the American Psychological Association), as have other federal agencies (e.g., Federal Trade Commission, 2000). Indeed, six medical and public-health professional organizations held a Congressional Public Health Summit on July 26, 2000, and issued a Joint Statement on the Impact of Entertainment Violence on Children. This statement noted that “entertainment violence can lead to increases in aggressive attitudes, values, and behavior, particularly in children.” The statement also concluded that the research points “overwhelmingly to a causal connection between media violence and aggressive behavior in some children” (Joint Statement, 2000, p. 1). The six signatory organizations were the American Academy of Pediatrics, American Academy of Child and Adolescent Psychiatry, American Medical Association, American Psychological Association, American Academy of Family Physicians, and American Psychiatric Association. These reports, coupled with mounting public concern, stimulated a search for ways to reduce the adverse effects of media violence, and were responsible, in part, for the passage of the Telecommunications Act of 1996, which mandated that new TV sets be manufactured with a V(for violence)-chip that permits parents to block objectionable content.
For a variety of reasons, it is now time for a new assessment of what is known scientifically about how media violence affects young people and what can be done to mitigate these adverse effects. The body of research on TV violence continues to grow, both in depth and in breadth. In addition, important changes are occurring in the landscape of entertainment-media use, and some of these changes have stimulated new areas of research. The rise of new media—particularly interactive media (such as video games and the Internet)—has introduced new ways children and youth can be exposed to violence. The roles of these new media in producing youthful violence should be considered in light of existing theory and new research. It is especially advisable to ascertain what contribution media violence makes to serious interpersonal physical violence among older children and adolescents given the current national concern about this problem.
It is also important to present this report because of the disparity between, on one side, the actual research findings and, on the other side, the intransigent assertions made by a number of vocal critics. That is, although research shows the adverse effects of media violence, and there is increasing consensus among researchers in this area about these effects, the critics continue to pronounce that media violence cannot be affecting youth (e.g., Fowles, 1999; Freedman, 1984, 2002; Rhodes, 2000). Also indicative of this difference in views, a recent statistical analysis of the media-violence research (Bushman & Anderson, 2001) demonstrated that although the scientific evidence has grown considerably stronger over the past three decades, recent news reports imply that the scientific evidence is weaker than did earlier news reports.
In this report, we do not deal directly with recent critiques of the field. A number of carefully reasoned essays already point out flaws in the critiques and explain why the proposition that media violence can have adverse effects on its audience is so strongly opposed by various interest groups (Bushman & Anderson, 2001; Hamilton, 1998; Huesmann, Eron, Berkowitz, & Chaffee, 1992; Huesmann & Moise, 1996; Huesmann & Taylor, 2003). Rather, our purpose is to summarize current scientific knowledge about five critical questions:
• What does research say about the relation—both short-term and long-term—between media violence and aggressive and violent behavior? (Overview of Empirical Research)
• How does media violence produce its effects on aggressive and violent behavior? (Theoretical Explanations)
• What characteristics of media violence are most influential, and who is most susceptible to such influences? (Research on Moderator Effects)
• How widespread and accessible is violence in the media (television, movies, music videos, video games, Internet)? (Research on Media Use and Content)
• How can individuals and society counteract the influence of media violence? (Research on Interventions)
We summarize our observations in the Discussion section, which also identifies crucial areas for additional research.
In reading through this monograph, a few important points should be kept in mind: First, researchers investigating the impact of media violence on youth have focused mostly on how it affects the viewer’s aggression. Aggression is defined by psychologists as any behavior that is intended to harm another person. There are many forms of aggression. For example, verbal aggression usually refers to saying hurtful things to the victim. Relational or indirect aggression refers to behavior that is intended to harm the target person but is enacted outside of the target person’s view (e.g., behind his or her back), such as telling lies to get the person in trouble or to harm his or her interpersonal relationships. The aggressive behaviors of greatest concern usually involve physical aggression. Physical aggression may range in severity from less serious acts, such as pushing or shoving, to more serious physical assaults and fighting, extending to violent acts that carry a significant risk of serious injury. There is no clear-cut consensus-based line separating “violence” from milder forms of physical aggression, nor is one needed to understand the research findings on media violence. We use the term violence to refer to the more extreme forms of physical aggression that have a significant risk of seriously injuring their victims.
Some studies have focused on the impact of media violence on aggressive thinking, including beliefs and attitudes that promote aggression. Other studies have focused on the influence of media violence on aggressive emotions —that is, on emotional reactions, such as anger, that are related to aggressive behavior. It is important to keep these three types of outcome variables (behavior, thoughts, emotions) separate, and to reserve the labels “aggression” and “violence” for behaviors intended to harm another person.
Second, as we and others have frequently noted, the weight of evidence indicates that violent actions seldom result from a single cause; rather, multiple factors converging over time contribute to such behavior. Accordingly, the influence of the mass media is best viewed as one of the many potential factors that help to shape behavior, including aggression. When we use causal language, we do not mean that exposure to media violence is either a necessary or a sufficient cause of aggressive behavior, let alone both necessary and sufficient (Anderson & Bushman, 2002c). To our knowledge, no media-violence researcher has ever made such an extreme claim. The 14-year-old boy arguing that he has played violent video games for years and has not ever killed anybody is absolutely correct in rejecting the extreme “necessary and sufficient” position, as is the 45-year-old two-pack-a-day cigarette smoker who notes that he still does not have lung cancer. But both are wrong in inferring that their exposure to their respective risk factors (violent media, cigarettes) has not causally increased the likelihood that they and people around them will one day suffer the consequences of that risky behavior.
Third, a developmental perspective is essential to an adequate understanding of how media violence affects youthful conduct and to the formulation of a coherent public-health response to this problem. Most youth who are aggressive and engage in some forms of antisocial behavior do not go on to become violent teens and adults. However, research has shown that a significant proportion of aggressive children are likely to grow up to be aggressive adults, and that seriously violent adolescents and adults often were highly aggressive and even violent as children. In fact, the best single predictor of violent behavior in older adolescents and young adults is aggressive behavior when they were younger (Huesmann & Moise, 1998; Tremblay, 2000). Thus, influences that promote aggressive behavior in young children can contribute to increasingly aggressive and ultimately violent behavior many years later. It is therefore important to identify factors—including media violence— that, singly and together, may play a role in these outcomes in childhood.
Fourth, it is important to avoid the error of assuming that small statistical effects necessarily translate into small practical or public-health effects. There are many circumstances in which statistically small effects have large practical consequences. Perhaps the most relevant circumstances are when small effects accumulate over time and over large proportions of the relevant population. For example, when Abelson (1985) asked a group of Yale University psychology scholars knowledgeable both about the concept of statistical variance and about baseball “to estimate what percentage of the variance in whether or not the batter gets a hit is attributable to skill differentials between batters” (p. 131), he found that these statistically sophisticated psychologists greatly overestimated the variance due to skill differences. The median estimate was 25%, whereas the correct statistical answer is actually about 0.3%. But this small effect of batting-skill differences has a huge impact on outcomes such as team win/loss records, career runs batted in, league championships, and World Series championships, because even small differences in batting skill accumulate across large numbers of times at bat within a season and across a career.
Similarly, even small statistical effects of media violence on aggressive behavior can have important societal consequences for at least three different reasons. First, a large portion of the population (almost everyone, in fact) is exposed to this risk factor (accumulation across a large population). Second, the deleterious effects of exposure to media violence are likely to accumulate (via learning) within the individual with repeated exposure. Third, even short-lived effects of a single exposure (via priming effects—see the Theoretical Explanations section) can add significant amounts of aggression and violence to society because at any given waking hour a large portion of the population either is currently being exposed to violent media or has been exposed to such violence within the past 20 min.
Medical scientists and public-health officials seem to have avoided the problem of underestimating the public-health importance of small effects by translating their findings into cancer rates or heart attack rates or death rates for the entire U.S. population, but behavioral scientists have not traditionally done this type of population-rate translation. Thus, people are frequently shocked to learn that many behavioral science effects are considerably larger than key medical science effects that are deemed extremely important (e.g., Bushman & Huesmann, 2001). For example, Rosenthal (1990) reported that the major study on aspirin’s ability to reduce heart attacks was stopped prematurely because the initial results were so strong that it was deemed ethically irresponsible to continue giving placebos to the control group; aspirin’s effect accounted for about 0.1% of the variance. Our point: Conclusions about small statistical effect sizes need to be made with caution and in this broader context.
Finally, it must be recognized that the firmest evidence about the effects of media violence, or any other presumed causal influence, on aggression is provided by true experiments in which participants are randomly assigned to conditions experiencing different “doses” of the factor under investigation. There have been many such experiments involving media violence. Out of ethical necessity, these generally have not examined effects on the most serious types of physical aggression. However, longitudinal studies (as reviewed in a later section) reveal that children who exhibit relatively high levels of the mild forms of aggression common in childhood are more likely than other children to engage in more severe forms of aggression in adolescence and adulthood. Similarly, methodological research designed to test the generality of laboratory measures of aggression (e.g., Anderson & Bushman, 1997; Carlson, Marcus-Newhall, & Miller, 1989) has demonstrated that high levels of the mild forms of aggression typical of laboratory studies correlate well with each other and with more extreme forms of physical aggression measured in real-world contexts. Consequently, experiments on media violence add significantly to understanding of the causal effects of media violence on aggression, and are especially valuable when their findings are integrated with the results of more naturalistic surveys and longitudinal studies dealing with serious forms of physical aggression and violence. In other words, no single methodological approach can provide unequivocal answers to the key questions about media violence, but converging results from studies using multiple methodologies can enhance confidence in the validity of the conclusions drawn. This triangulation approach to science is effective precisely because different methodologies have different inherent strengths and weaknesses, and converging results essentially rule out competing alternative explanations (e.g., Anderson & Bushman, 2001).
OVERVIEW OF EMPIRICAL RESEARCH ON MEDIA VIOLENCE AND AGGRESSION
Most studies of the effects of media violence have examined passive visual media (dramatic television and movies, television news, and music videos), that is, media that viewers observe only. However, there have also been a limited number of investigations of interactive visual media (video games and the Internet), media that viewers both observe and interact with. In this section, we examine both kinds of studies. Within each genre, we begin with experimental studies, in which cause and effect are unambiguous but the effects observed are short term. Of necessity, the outcomes in these experiments tend to be physical aggression that is not life threatening, or else verbal aggression, aggressive thoughts, or aggressive emotions. We then turn to surveys, or cross-sectional studies, that provide a snapshot of the relation at one point in time between individuals’ habitual consumption of media violence and their aggressive behavior. [1] These surveys often deal with more serious forms of physical aggression, but this type of methodology by itself is not as conclusive about causation as experimental studies are. For genres for which longitudinal studies exist, we conclude our review by examining how youths’ habitual consumption of violence affects their violent and aggressive behavior later in life. Like cross-sectional investigations, longitudinal studies often examine serious physical aggression, but they generally provide better evidence about causal influences than can cross-sectional studies.
Because of space constraints, we provide illustrative examples of carefully selected key studies in each area, rather than an exhaustive review of the research literature. However, in addition to discussing these selected studies, we describe (if available) meta-analyses that have aggregated the results of most major investigations to reach overall estimates of effect sizes. A meta-analysis essentially averages the effect sizes of multiple studies, and allows the researcher to ask whether a particular factor (e.g., exposure to media violence) is significantly linked to a particular outcome (e.g., violent behavior). There are several commonly used measures of effect size, any of which can be applied to experimental, correlational, and longitudinal types of studies. To provide a common metric for this discussion, we have converted all effect sizes to correlation coefficients (rs).
Dramatic Television and Movies
Randomized experiments: Examples
A substantial number of laboratory and field experiments over the past half-century have examined whether exposure to violent behavior on film or television tends to increase aggressive behavior in the short term (see reviews by Bushman & Huesmann, 2001; Comstock, 1980; Geen, 1990; Geen & Thomas, 1986; Huesmann, Moise, & Podolski, 1997). The consistent finding from such randomized experiments is that youths who watch violent scenes subsequently display more aggressive behavior, aggressive thoughts, or aggressive emotions than those who do not.
In the typical experimental paradigm, researchers randomly assign youths to see either a short violent or a short nonviolent film, and then observe how they interact with other people after viewing the film. Both physical and verbal aggression toward others may be assessed. The time period for testing the effects is short—from a few minutes to a few days after seeing the film—and generally there is no attempt to test for lasting effects of the single exposure. With older teenagers and college students, physical aggression has often been measured by the willingness of participants to inflict an electric shock or a loud aversive noise on a peer. This person has sometimes been an individual who provoked them earlier, but in other investigations has been a neutral bystander. The participants are typically given a weak rationale for harming the other person (e.g., the punishment is an unfavorable evaluation of the peer’s work on an assigned task).
In the following paragraphs, we describe several studies selected from the large number of studies of this type, in part because their outcome measure was physical aggression against another person, in part because the authors reported enough information that effect sizes could be computed, and in part because they illustrate the wide range of settings, participant populations, experimental procedures, and measures used.
Bjorkqvist (1985) exposed 5- to 6-year-old Finnish children to either violent or nonviolent films. Two raters who did not know which type of film the youngsters had seen then observed the children playing together in a room. Compared with the children who had viewed the nonviolent film, those who had just watched the violent film were rated much higher on physical assault (hitting other children, wrestling, etc.), as well as other types of aggression. The results for physical assault were highly significant (p <.001), and the effect size was substantial (r - .36).
Josephson (1987) randomly assigned 396 seven- to nine-year- old boys to watch either a violent or a nonviolent film before they played a game of floor hockey in school. Observers who did not know what movie any boy had seen recorded the number of times each boy physically attacked another boy during the game. Physical attack was defined to include hitting, elbowing, or shoving another player to the floor, as well as tripping, kneeing, pulling hair, and other assaultive behaviors that would be penalized in hockey (the only verbal act included in the measure was insulting another player with an abusive name). One added element in this study was that a specific cue that had appeared in the violent film (a walkie-talkie) was carried by the hockey referees in some conditions. This particular cue presumably reminded the boys of the movie they had seen earlier. Josephson found that for aggressive boys (those who scored above average on a measure of aggressiveness), the combination of seeing a violent film and seeing the movie-associated cue stimulated significantly more assaultive behavior than any other combination of film and cue (p <.05). The effect size was moderate (r = .25).
Two related randomized experiments demonstrated that exposure to media violence can lead to increased physical assaults by teenage boys, at least in the short run. In a home for delinquent boys in Belgium, Leyens, Camino, Parke, and Berkowitz (1975) assigned boys in two cottages to see violent movies every night for five nights while boys in the other two cottages saw nonviolent films. The boys were observed interacting after the movies each evening and were rated for their frequency of hitting, choking, slapping, and kicking their cottage mates. Those boys who were exposed to the violent films engaged in significantly more physical assaults (p <.025) on their cottage mates. The effect sizes for such physical aggression were not published, but the best estimates from the published data suggest a substantially larger effect for the boys who were initially more aggressive (r = .38) than for the boys who were initially less aggressive (r = .14). In similar field experiments with American youth in a minimum-security penal institution for juvenile offenders, Parke, Berkowitz, Leyens, West, and Sebastian (1977) found similar effects of exposure to violent films on overall interpersonal attacks (physical or verbal), although they did not report the effects on frequency of physical assault separately. These two experiments are especially important because they demonstrate that violent movies can generate serious physical aggression even in a setting where this behavior is counter to officially prescribed rules.
Although witnessed violence can evoke aggression in people who are not highly emotionally aroused at the time, several experiments have shown that emotionally or physically excited viewers are especially apt to be aggressively stimulated by violent scenes. For example, in the experiment by Geen and O’Neal (1969), college men who had been provoked by another student and who were also exposed to loud noise shocked their provocateur significantly more intensely (p <.01) after they had watched a film of a prizefight than after they had seen a movie of a track meet. The effect size was quite large (r = .75) and seemed to be accentuated by the viewers’ noise-generated excitement. This study has been replicated with variations of film content and provocation with essentially identical results (see Berkowitz, 1993).
Finally, Donnerstein and Berkowitz’s (1981) study demonstrated that combining violent portrayals with sexual stimulation is particularly potent at stimulating male viewers to be more physically assaultive toward females who have provoked them. In this experiment, male university students watched either a movie portraying sex and violence, a nonviolent sex film, or a movie that was neither sexual nor violent and were then given an opportunity to retaliate against a woman who had angered them earlier, by giving her electric shocks. The men who had viewed the violent sex film punished the woman more intensely than did their counterparts who had watched either the neutral film or the nonviolent sex movie. Again, the effect size was quite large (r = .71).
The six key experiments we have just reviewed all examined the immediate causal effect of media violence on physical aggression. A great many studies have also examined the immediate effect of media violence on aggressive thoughts or emotions (for reviews, see Berkowitz, 1993; Bushman & Huesmann, 2001; Geen, 2001; Rule & Ferguson, 1986). These studies are important to consider because research has shown that the risk of physically aggressive behavior against other people is increased among youth who believe that violence against others is acceptable (Huesmann & Guerra, 1997), in part because they believe that their targets are “bad” people and that punishing them is justified (e.g., Berkowitz, 1965; Berkowitz & Geen, 1967). Similarly, people who accept violence toward females (Byers & Eno, 1991; Lackie & de Man, 1997), who view others as being hostile (Dodge & Frame, 1982), who believe that retaliation is “honorable” (Nisbett & Cohen, 1996), who fantasize about violence (Rosenfeld, Huesmann, Eron, & Torney-Purta, 1982), or who just simply think about violent words (Carver, Ganellen, Froming, & Chambers, 1983) also are at high risk for physical aggression against others.
Typically, randomized experiments reveal that exposure to media violence can cause immediate increases in aggressive thoughts and tolerance for aggression in both children and older youth. For example, in studies with young children (Drabman & Thomas, 1974, 1975; Thomas & Drabman, 1975), youngsters shown a brief violent film clip were slower to call an adult to intervene when they saw two younger children fighting than were peers who had watched a neutral film. The single violent clip appeared to make the children more tolerant of aggression, at least temporarily. Similarly, Malamuth and Check (1981) found an increased acceptance of physical aggression toward women by college men several days after they had watched violent sex scenes. Still other studies have shown that college students randomly assigned to view a short violent film segment display more aggressive thoughts (e.g., Bushman, 1998) or more aggressive emotions (e.g., Anderson, 1997) than comparable students who are assigned to view a nonviolent film segment. Using a somewhat longer time frame, Zillmann and Weaver (1999) reported an experiment in which college-age males and females viewed either four violent or four nonviolent feature films on consecutive days. One day after viewing the last film, all participants took part in a supposedly unrelated study in which level of hostile behavior was assessed. Those who previously had seen the violent films exhibited significantly more hostility than did those who previously had seen the nonviolent films.
Randomized experiments: Meta-analysis and summary
Three meta-analyses in the past 15 years have computed the overall effect sizes for randomized experiments investigating the influence of TV and movie violence on aggression (Hearold, 1986; Paik & Comstock, 1994; Wood, Wong, & Chachere, 1991). The most recent and comprehensive of these was the analysis of Paik and Comstock, who examined effect sizes from 217 studies published between 1957 and 1990. On the basis of 432 independent tests of effects in the randomized experiments they reviewed, Paik and Comstock found a moderate to large average effect size (r = .38). When the analysis was limited to experiments in which the outcome was classified as physical violence against a person, the 71 independent effect sizes yielded an average r of .32. The studies in the review reported 32 independent effect sizes for criminal violence against a person; among this group, the average effect size was smaller but still significant, r = .13.
In summary, many well-controlled, randomized experiments have examined how exposure to violent TV and film media affects aggression in youths of all ages. The evidence from these experiments is compelling. Brief exposure to violent dramatic presentations on TV or in films causes short-term increases in youths’ aggressive thoughts, emotions, and behavior, including physically aggressive behavior serious enough to harm others. The effect sizes are moderate on the average but vary greatly depending on the outcome measure used; usually, effect sizes are smaller for more serious outcomes than for less serious outcomes. There is some evidence that youth who are predisposed to be aggressive or who recently have been aroused or provoked are somewhat more susceptible to these effects than other youngsters are, but there is no evidence of any totally immune group. The average effect sizes, even for relatively serious physical aggression, are large enough to warrant social concern.
Cross-sectional surveys: Examples
Cross-sectional surveys over the past 40 years have consistently provided evidence that the current physical aggression, verbal aggression, and aggressive thoughts of young people are correlated with the amount of television and film violence they regularly watch (see reviews by Chaffee, 1972; Comstock, 1980; Eysenck & Nias, 1978; Huesmann & Miller, 1994). Moreover, the studies reporting significant correlations have used a variety of research methods and examined youngsters of different ages and from different cultures (e.g., Huesmann & Eron, 1986). In some studies, the aggression assessed has included physically aggressive acts serious enough to fit our definition of violence. For example, McLeod, Atkin, and Chaffee (1972) studied the correlations between “aggressive behavioral delinquency” (fighting, hitting, etc.) and viewing of TV violence in samples of Wisconsin and Maryland high school and junior high school students. They found significant correlations ranging from .17 (p < .05) to .28 (p < .01) for both males and females. In a study of English 12- to 17-year-old males, Belson (1978) reported 49% more violent acts in the past 6 months by heavy TV violence viewers than by light violence viewers.
The cross-sectional correlations have generally been in the small to moderate range. On the average, they have been slightly higher for elementary-school children than for teenagers and adults, particularly when general aggression is assessed. For example, Eron, Huesmann, Lefkowitz, and Walder (1972) obtained a significant correlation of .21 for 8-year-old boys and a nonsignificant correlation for the same boys when they were 19. Similarly, Huesmann, Moise-Titus, Podolski, and Eron (2003) reported a correlation of .18 (p <.05) between TV-violence viewing and general aggression for 6- to 10-year-old males, but a nonsignificant correlation between general aggression and concurrent TV-violence viewing for the same males when they were in their 20s. For females in their 20s, however, Huesmann et al. reported a significant correlation (r = .23, p < .01). Other studies also have found significant correlations at older ages.
Cross-sectional surveys: Meta-analysis and summary
Paik and Comstock’s (1994) meta-analysis examined cross-sectional surveys published between 1957 and 1990. For 410 tests of the hypothesis that viewing television violence is positively correlated with aggressive behavior, they reported an average r of .19. Perhaps more important for the current review, these authors identified 200 tests of the hypothesis in which the dependent measure of aggressive behavior was actual physical aggression against another person. The effect size was essentially the same for these studies as for all surveys combined (i.e., r = .20).
These cross-sectional surveys provide convincing evidence that frequent viewing of violence in the media is associated with comparatively high levels of aggressive behavior. The surveys also support the causal conclusions of the experimental studies, and suggest that findings of short-term effects in the laboratory may well be generalizable to longer-term effects on real-world aggression. However, these cross-sectional surveys alone do not indicate whether media violence causes aggression, whether aggressive youth are attracted to media violence, or whether some other factor predisposes the same youth to both watch more violence and behave more aggressively than their peers. Longitudinal surveys investigating the subsequent effects of exposure to media violence at an early age provide better evidence regarding these possibilities.
Longitudinal surveys: Examples
A small group of studies have examined the effects of television violence on aggressive behavior over time. Four of the key studies are discussed here. In a study of a representative sample of 856 youth in Columbia County, New York, beginning in 1960, Eron and his colleagues found that a boy’s exposure to media violence at age 8 was significantly related to his aggressive behavior 10 years later, after he graduated from high school (r = .31, N = 184, p < .01; Eron et al., 1972; Lefkowitz, Eron, Walder, & Huesmann, 1977). At both times, aggressive behavior was measured primarily by peer nomination, a technique in which the youths answer a series of questions about their classmates’ aggressiveness. The researchers assessed both physical aggression (e.g., “Who pushes and shoves other kids?”) and verbal aggression (e.g., “Who makes up stories and lies to get other kids in trouble?”). The longitudinal correlation remained above .25 even when there was statistical control of other potentially relevant factors, such as initial aggressiveness of the child, IQ of the child, family socioeconomic status (SES), parents’ aggressiveness, and parents’ punishment and nurturance of the child. Furthermore, additional statistical analyses evaluating the connection between scores at the two ages cast doubt on the possibility that the longitudinal relation was merely a consequence of highly aggressive youth liking to watch more violence than their less aggressive counterparts. Aggressiveness at age 8 did not predict viewing of violence at age 18. In contrast to the findings obtained for the boys (and to the results obtained in other investigations—see Huesmann & Eron, 1986; Huesmann, Lagerspetz, & Eron, 1984; Huesmann et al., 2003), the findings for the girls revealed no relation between exposure to TV violence and aggressive behavior.
In a longitudinal study of boys and girls ages 7 to 16 from two Midwestern cities (conducted by the NBC television company), Milavsky, Kessler, Stipp, and Rubens (1982) examined the effects of television violence on aggression using measures that included serious physical aggression and delinquency. The youth were surveyed up to five times during a 3-year period (1970– 1973). Cross-sectional correlations between viewing of TV violence and concurrent levels of aggression were obtained for the total sample within each time of assessment; they were significant and comparable to those found in most other cross-sectional studies, that is, .13 to .23 for boys and .21 to .37 for girls.
The investigators then examined the longitudinal correlations between aggressive behavior at one point in time and TV violence viewing at an earlier time, while statistically controlling for earlier aggression. They examined these correlations over 15 intervals ranging from 5 months to 3 years apart. For elementary-school boys, 12 of the 15 correlations were positive, although only 2 were statistically significant. Ten of the 15 correlations were positive for girls, although only 3 were statistically significant. A comparable analysis carried out in a subsample of teenage boys showed a positive correlation in 6 of 8 cases, but only 1 such “lag” yielded a significant effect. In all cases, adding SES as a covariate reduced the significant effects further. However, it should be noted that these predictive analyses were based on subsamples from which the research team had deleted the data of many of the most aggressive children (25% of boys and 16% of girls in the initial sample), because they supposedly had not reported their TV viewing accurately. Given that highly aggressive youths appear to be more likely than others to be aggressively stimulated by violent scenes, it may well be that discarding these data artificially decreased the reported effects.
In the late 1970s, Huesmann and his colleagues began a longitudinal study of the effects of TV violence in five countries (Huesmann & Eron, 1986; Huesmann et al., 1984; Huesmann et al., 2003). Representative samples of middle-class youth in each country were examined at three times as they grew from 6 to 8 or from 8 to 11 years of age. Aggression was assessed by peer nominations in response to questions about physical and verbal behaviors, among other things. The cross-sectional correlations between aggression and overall exposure to TV violence were positive and small to moderate in all countries, with significant correlations being obtained for both boys and girls in the United States. However, the extent to which earlier viewing of TV violence predicted later aggression varied substantially between the genders and among the countries. In the United States, girls’ viewing of TV violence had a significant effect (r = .17, p< .05) on their later aggression even after taking into account their early levels of aggression, SES, and scholastic achievement. For the boys in the U.S. sample, TV violence alone did not predict later aggression, but those who had watched violent programming frequently in their early childhood and who also reported a strong identification with aggressive TV characters were generally regarded by their peers as the most aggressive (r = .19, p < .05).
Fifteen years after the study started, more than 300 participants in the U.S. sample were reinterviewed when they were in their early 20s (Huesmann et al., 2003). Results from this 15-year follow-up suggest a delayed effect of media violence on serious physical aggression. The researchers found significant correlations between television violence viewing during childhood and a composite measure of aggression (physical, verbal, and indirect) during young adulthood, for both men (r = .21, n = 153, p < .01) and women (r = .19, n = 176, p .01). When the outcome examined was restricted to physical aggression or violence (e.g., punch, beat, choke, threaten or attack with a knife or gun), the correlations were still significant (rs = .17 and .15, respectively). Furthermore, when the people who had watched violent programs frequently in childhood were compared with their counterparts who viewed these programs much less often, it was found that the former, as adults, committed significantly more acts of physical aggression, such as having “pushed, grabbed, or shoved their spouses” (p. 210; 42% vs. 22% in the case of males) or “shoving, punching, beating or choking” (p. 210) someone who had made them angry (17% vs. 4% for females). Finally, analyses showed that for both men and women, frequent exposure to TV violence during childhood resulted in high levels of aggressive behavior later, whereas high aggressiveness during childhood did not lead to frequent viewing of television violence later.
These effects of frequent childhood exposure to TV violence on later aggression remained significant even when the researchers controlled statistically for parents’ education and children’s achievement. Although analyses of the data from the other countries are not yet completed, preliminary results indicate that childhood exposure to media violence also predicts adult aggression in males and females in Finland and in males in Israel, but not in Poland, where the social transition of the 1980s seems to have changed the relations (Huesmann & Moise-Titus, 1999; Viermero, 2002).
A final longitudinal study worth discussing examined effects of TV habits in adolescence and early adulthood on later violent behavior (J.G. Johnson, Cohen, Smailes, Kasen, & Brook, 2002). Total amount of television watching (rather than amount of violent TV viewing more specifically) was assessed at ages 14 and 22. Although this is not the ideal measure of violent TV exposure, the high proportion of television programs that contain violence (see the section on Violent Content of Media) suggests that, on average, those people who watch a lot of television usually are also getting the most exposure to violent TV. Moreover, in analyzing total time watching TV rather than the more specific time watching violent TV, the study probably underestimated the actual effect of exposure to violent television on later aggressive behavior (Anderson & Bushman, 2002a).
The most relevant results of this study have to do with effects on “assault or physical fights resulting in injury” (pp. 2469–2470), which was assessed at age 16 or 22 in one analysis, and at age 30 in another analysis. TV exposure at age 14 significantly predicted assault and fighting behavior at 16 or 22 years of age, even after controlling statistically for family income, parental education, verbal intelligence, childhood neglect, neighborhood characteristics, peer aggression, and school violence. The effect size across all participants was in the small range (r = .17). In addition, TV exposure at age 22 significantly predicted assault and fighting behavior at age 30; the size of this effect was in the medium range (r = .= 35). There were many additional findings of interest involving differences in effect size for males versus females at different time periods and for different measures of aggression. But the most important implication of this study is that television watching (and presumably exposure to violent TV) may have important adverse effects on much older populations than was previously believed.
Longitudinal surveys: Meta-analysis and summary
The only meta-analysis to look at longitudinal studies of media violence separately was conducted by Anderson and Bushman (2002c). Although this analysis pooled studies of all types of media violence, the great majority were investigations of violent TV. Anderson and Bushman found a statistically significant average effect size of .17 across 42 independent tests involving almost 5,000 participants. Given these meta-analytic results and the specific outcomes of the key longitudinal studies we have already discussed, it seems safe to draw a conclusion from this research: High levels of exposure to violent TV programs in childhood can promote aggression in later childhood, adolescence, and even young adulthood. The effect sizes are small to medium, depending on the time lag. There also is some evidence that more aggressive children tend to watch more violence than their less aggressive peers, but the evidence is stronger that seeing a lot of media violence is a precursor of increased aggression even when social class, intellectual functioning, prior level of aggressiveness, and parenting are statistically controlled. Furthermore, the most recent studies suggest that this increased aggression in young adulthood includes very serious forms of aggression and violence.
_small.gif)
