Agenda-setting is the creation of public awareness and concern of salient issues by the news media. Two basic assumptions underlie most research on agenda-setting:
the press and the media do not reflect reality; they filter and shape it;
media concentration on a few issues and subjects leads the public to perceive those issues as more important than other issues.
One of the most critical aspects in the concept of an agenda-setting role of mass communication is the time frame for this phenomenon. In addition, different media have different agenda-setting potential.
Rogers and Dearing[15] identify three types of agenda setting:
public agenda setting, in which the public's agenda is the dependent variable (the traditional hypothesis)
media agenda setting, in which the media's agenda is treated as the dependent variable (aka agenda building)
policy agenda setting, in which elite policy makers' agendas are treated as the dependent variable (aka political agenda setting)
Mass communication research, Rogers and Dearing argue, has focused a great deal on public agenda setting - e.g., McCombs and Shaw, 1972 - and media agenda setting, but has largely ignored policy agenda setting, which is studied primarily by political scientists. As such, the authors suggest mass communication scholars pay more attention to how the media and public agendas might influence elite policy maker's agendas (i.e., scholars should ask where the President or members of the U.S. Congress get their news from and how this affects their policies). Writing in 2006, Walgrave and Van Aelst took up Rogers and Dearing's suggestions, creating a preliminary theory of political agenda setting, which examines factors that might influence elite policy makers' agendas
