YOUTH VIOLENCE: A REPORT OF THE SURGEON GENERALhttp://www.surgeongeneral.gov/library/youthviolence/toc.html
MEDIA VIOLENCE: EXPOSURE AND CONTENThttp://www.surgeongeneral.gov/library/youthviolence/chapter4/appendix4bsec2.html#MajorBehavioralMedia
Long-term studies in which exposure to media violence in early childhood is related to later aggression and violence (such as aggravated assault, robbery, rape, and homicide) can identify the enduring effects of media violence. In most such studies to date, however, aggression, not violence, has been the primary outcome measured. In the absence of a meta-analysis, the findings of three frequently cited longitudinal studies on the effects of media violence are discussed briefly below. Studies examining effects over shorter time periods (Singer et al., 1984) or with international samples (Huesmann & Eron, 1986) are not included here.
In a study begun in 1960 on a sample of 875 youths in New York State, Eron and colleagues found that for boys, but not for girls, exposure to media violence at age 8 was significantly related to aggressive behavior a decade later (r = .31, N = 211, p < .01) (Eron et al., 1972; Lefkowitz et al., 1977). At both times, peers assessed physical and verbal aggression. The longitudinal correlation remained above .25, even in separate analyses statistically controlling for factors such as the child’s initial aggressiveness, the child’s intelligence, family SES, parents’ aggressiveness, and parents’ punishment and nurturance of the child.
Milavsky et al. (1982) examined the probability of initiating aggression after exposure to violence on television in 2,400 boys and girls age 7 to 12 from two midwestern cities who had been surveyed up to six times between 1970 and 1973. A sample of 800 teenage boys5 was studied at five times to identify the effect of violent television on aggression and violence. For the elementary school sample, the average cross-sectional correlation between exposure to media violence and personal aggression was small for boys (r = .17) and large for girls (r = .30). The researchers then attempted to predict aggressive behavior at one point in time from the extent to which children viewed television violence at an earlier time, while controlling for earlier aggressive characteristics. They examined this prediction over 15 time intervals ranging from 5 months to 3 years apart. For elementary school boys, only 2 of the 15 predictions at different intervals were statistically significant. For girls, only three predictions were statistically significant. In the teenage male sample, only one of eight correlations was significant. In only one of nine analyses using measures of violence (for example, knife fight, car theft, mugging, gang fight) were boys with greater exposure to television violence more likely to initiate violence 2 years later than those with less exposure.
The third longitudinal study of media violence effects began in the late 1970s and spanned five countries (Huesmann et al., submitted; Huesmann et al., 1984; Huesmann & Eron, 1986). In each locale, samples of middle-class youths were examined three times between age 6 to 8 or age 8 to 11. Both physical and verbal aggression were assessed by peers. The correlations between aggression and overall viewing of television violence at a single point in time were small to moderate and often significant. In the United States, the 3-year average correlation was moderate for boys and for girls (r = .25 and r = .29, respectively; p < .001). The predictive power of viewing television violence for childhood aggression a year later varied substantially. In the United States, girls’ viewing of television violence had a significant effect (b = .17, N = 89, p < .05) on their later aggression, even after accounting for early levels of aggression, SES, and scholastic achievement. For boys, television violence alone did not predict later aggression. When the investigators took into account both exposure to television violence and identification with aggressive television characters, they found a positive relation with aggressiveness (b = .19, N = 84, p < .05).
A follow-up study of over 300 people in the U.S. sample 15 years later suggested that media violence has a delayed effect on aggression (Huesmann et al., submitted). There was a small to moderate longitudinal correlation between childhood television viewing and a composite measure of young adult aggression (physical, verbal, and indirect aggression) for both men (r = .21, N = 153, p < .01) and women (r = .19, N = 176, p < .01). When the outcome was limited to physical aggression, the correlations were smaller (r = .17 and r = .15, respectively). Furthermore, women who had watched relatively more television violence as girls committed significantly more specific acts of violence as adults, such as "punching, beating, or choking another adult," than did the other women (17 percent versus 4 percent). There were no significant differences among the men. Other analyses showed that effects remained significant even when researchers controlled for parent education and children’s scholastic achievement (b = .19 for boys, b = .17 for girls, p < .05). In addition, aggressive behavior did not significantly increase boys’ or girls’ viewing of television violence (b = .08 for boys and b = .04 for girls; p = ns).
In summary, these longitudinal studies show a small, but often statistically significant, long-term relationship between viewing television violence in childhood and later aggression, especially in late adolescence and early adulthood. Some evidence suggests that more aggressive children watch more violence, but the evidence is stronger that watching media violence is a precursor of increased aggression.
Other studies have explored the behavioral impact of introducing television in several countries (Centerwall, 1989a, 1989b, 1992; Joy et al., 1986; Williams, 1986). These studies indicate that when television was introduced, aggression and violence increased. The findings must be viewed with caution, however, because they do not take into account a range of other factors that may influence national crime rates and the amount of violence watched on television.
Despite anecdotal reports of a "contagion of violence," relatively little systematic research has examined whether seeing or hearing about violence in news coverage encourages violent or aggressive behavior. On the whole, the limited data available support the notion of a contagion effect. This evidence is derived from studies examining how reports of a well-known person’s suicide affect the likelihood of imitative suicide (Phillips, 1979, 1982; Simon, 1979; Stack, 1989). Other studies of the contagion effect (Berkowitz & Macaulay, 1971; Phillips, 1983) have been questioned because of their research methods and the ambiguity of their results (Baron & Reiss, 1985; see Phillips & Bollen, 1985 for a response). This area merits additional research.
Violence in Other Media
Theoretically, the effects of exposure to media violence extend to Internet media as well. To date, however, no studies have been published regarding the effects of Web-based media violence on youth aggression and violence.
A relatively small amount of research has focused on the impact of music videos with violent or antisocial themes (Baxter et al., 1985; Caplan, 1985; Hansen & Hansen, 1990; Johnson et al., 1995a, 1995b; Rich et al., 1998). Randomized experiments indicate that exposure to violent or antisocial rap videos can increase aggressive thinking, but no research has yet tested how such exposure directly affects physical aggression.
The impact of video games containing violence has recently become a focus of research because children are theoretically more susceptible to behavioral influences when they are active participants than when they are observers. To date, violent video games have not been studied as extensively as violent television or movies. The number of studies investigating the impact of such games on youth aggression is small, there have been none on serious violence, and none has been longitudinal.
A recent meta-analysis of these studies found that the overall effect size for both randomized and correlational studies was small for physical aggression (r = .19) and moderate for aggressive thinking (r = .27) (Anderson & Bushman, in press). In separate analyses, the effect sizes for both randomized and cross-sectional studies was small (r = .18 and .19, respectively). The impact of video games on violent behavior remains to be determined.
Potential Moderators of Behavioral Effects
Research suggests that not all youths are affected in the same way by viewing media violence. Factors that appear to influence the effects of media violence on aggressive or violent behavior include characteristics of the viewer (such as age, intelligence, aggressiveness, and whether the child perceives the media as realistic and identifies with aggressive characters) and his or her social environment (for example, parental influences), as well as aspects of media content (including characteristics of perpetrators, degree of realism and justification for violence, and depiction of consequences of violence).
Evidence that these factors moderate the influence of media violence is limited, and it is more relevant to aggression than to violence. For example, studies of responses to violent television and films and violent video games have found that people who were initially more aggressive than other subjects were more affected in behavior, thoughts, and emotions (Anderson & Dill, 2000; Bushman, 1995; Bushman & Geen, 1990; Friedrich & Stein, 1973; Josephson, 1987). Research in this area clearly suggests that the impact of violent television, film, and video games on aggression is moderated by viewers’ aggressive characteristics.
Evidence that other individual, environmental, and content factors moderate the effects of exposure to media violence is less clear. Some studies suggest that these factors may buffer or enhance effects, but few have tested for such influences. Although limited in scope and depth, such studies provide clues to potential avenues for prevention efforts. For example, preliminary data point to the potentially vital role of parents in supervising their children’s exposure to violent media and in helping them interpret it (Nathanson, 1999)."
so essentially junk in junk out