and violent behavior measured in the laboratory, in the
field, and across substantial time spans. A set of well-
articulated theories explain why aggression generally
increases after exposure to violence in the media.
Additional research on viewer characteristics has
refined notions of who is most likely to be influenced
by media violence and under what circumstances
they are likely to be affected. More recent research
has focused on the effects of interactive media such
as video games. This research demonstrates effects
that are equivalent for this form of media to older
media use.Effects of Television and Movie
Violence on Aggressive Behavior
Most research on media violence and viewer aggres-
sion has focused on viewers who are passively
exposed to movies and television portrayals. A rela-
tively large number of laboratory experiments in
which subjects are randomly assigned to view film or
television violence and compared with control groups
have been conducted over the past 50 years. Several
types of aggression toward others have been assessed
in these studies, including verbal and physical aggres-
sion. These experiments have consistently found that
young people who watched violent scenes subse-
quently displayed more aggressive thoughts, emo-
tions, and behaviors than those who did not. Usually,
these laboratory studies measure the immediate
impact of violence exposure on aggression. Results
from these studies have shown that, for example,
children who watched television violence were more
likely to be rated as high on physical assault (hurting
other children, wrestling, as well as other types of
aggression) by observers who did not know which
type of film the children had seen. Field experiments
in which boys at a summer camp had been assigned to
view violent or nonviolent films and then observed
revealed that boys who had been assigned to the vio-
lent film conditions engaged in significantly more
physical assaults on fellow campers. This effect was
particularly pronounced for boys who were individu-
ally higher on trait aggression. Other research has
demonstrated that combining violent stimuli with
other arousing activities or portrayals can enhance the
aggression effect following exposure. For example,
college students who have been provoked by others or
who have seen sexually arousing films that portray
sex and violence exhibit pronounced increases inretaliatory behavior as indexed by their willingness to
deliver what they believe are electric shocks to other
subjects.
Randomized laboratory experiments have also
demonstrated desensitization effects, whereby children
subjects exposed for prolonged periods to media vio-
lence were slower to call an adult to intervene when
they saw two younger children fighting. Adults exhibit
similar desensitization effects including acceptance of
physical aggression toward females and hostile behav-
ior after prolonged exposure to violent movies com-
pared with adults in control conditions.
Meta-analyses that have computed the overall
effect sizes for randomized experiments have gener-
ally concluded that the size of the effect for the media
violence aggressive behavior effect is moderate to
large ranging from r=.3 to r=.4 for aggression;
effect sizes for criminal violence are smaller.
Survey research in which cross sections of elemen-
tary school children and adolescents have been sur-
veyed regarding their exposure to violence in the
media and measured on various indexes of general
aggression have yielded results similar to those in lab-
oratory and field experiments. These surveys show
that children and adolescents who report violence
viewing also exhibit higher levels of aggressive
behavior. Longitudinal studies designed to study the
effects of television violence on behavior over time
and thus are able to measure exposure to violence in
television before aggressive behavior is assessed pro-
vide evidence of a media violence aggression causal
link over time. Studies that have measured assault or
physical fights resulting in injury have found that
exposure to violence in television at age 14 signifi-
cantly predicted assault and fighting at later ages
including at 22 and 30 years.
Less well-known are the effects of exposure to
news violence, such as news of executions or assassi-
nations, on violent behavior. Likewise, a few experi-
mental studies of music videos and behavior have
been conducted, but the research is rather sparse.
Several studies of music videos have shown that ado-
lescents assigned to view violent rap music videos
increased endorsement of violent behavior.
Studies that have examined the introduction of tele-
vision into communities that have not had it have also
been undertaken. This work has tended to reinforce
findings from laboratory experiments and surveys.
One study, for example, found an increase in children’s
level of aggression in a Canadian community after theMedia Violence and Behavior——— 483M-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 483