Page 16 - Media Effects Advances in Theory and Research

1. NEWS INFLUENCE ON OUR PICTURES OF THE WORLD 5

age subsequently declined, so did the size of the constituency expressing
concern about Germany’s energy supply.
Agenda-setting at the local level occurred in the October 1997 legisla-
tive elections in the Buenos Aires metropolitan area (Lennon, 1998). Cor-
ruption was prominent on both the public and media agendas throughout
the fall, always ranking first or second. In September, the public agenda
and the combined issue agenda of five major Buenos Aires newspapers
only modestly agreed ( .43). As election day approached in October, the
correspondence between the agendas soared to .80, an increase that sug-
gests considerable learning from the news media in the closing weeks of
the election campaign (Weaver, 1996).
These real-world examples of agenda-setting effects are compelling but
are not the best evidence for the core, causal proposition of agenda-
setting. The best evidence that the news media are the cause of these
kinds of effects comes from controlled laboratory experiments, a setting
where the theorized cause can be systematically manipulated, subjects are
randomly assigned to various versions of the manipulation, and system-
atic comparisons are made among the outcomes.
Changes in the salience of defense preparedness, pollution, arms con-
trol, civil rights, unemployment, and a number of other issues were pro-
duced in the laboratory among subjects who viewed TV news programs
edited to emphasize a particular issue (Iyengar & Kinder, 1987). A variety
of controls were used to show that changes in the salience of the manipu-
lated issue were actually due to exposure to the news agenda. For exam-
ple, in one experiment, control subjects viewed TV news programs that
did not include the issue of defense preparedness. The change in salience
of this issue was significantly higher for the test subjects than for the sub-
jects in the control group. In contrast, there were no significant differences
between the two groups from before to after viewing the newscasts for
seven other issues.
A recent experiment documented the agenda-setting effects of an
online newspaper. The salience of racism as a public issue was signifi-
cantly higher among subjects exposed to various versions of an online
newspaper that discussed racism than among those subjects whose online
newspaper did not contain a news report on racism (Wang, 2000).
These studies are far from all of the accumulated evidence that sup-
ports the theory of agenda-setting. A meta-analysis of 90 empirical
agenda-setting studies found a mean correlation of .53, with most
about six points above or below the mean (Wanta & Ghanem, forthcom-
ing). There are, of course, a number of significant influences that shape
individual attitudes and public opinion. How a person feels about a par-
ticular issue may be rooted in his or her personal experience or in the
general culture or exposure to the mass media (Gamson 1992). But the