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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 Media Violence 19 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 Anderson, Berkowitz, Donnerstein, Huesmann, Johnson, Linz, Malamuth, & Wartella 20 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 < .0...
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