According to the agenda-setting theory, first developed by Prof. Maxwell McCombs and Prof. Donald Shaw in their Chapel Hill study (1968), mass media sets the agenda for public opinion by highlighting certain issues. In studying the way political campaigns were covered in the media, Shaw and McCombs found that the main effect of the news media was to set an agenda, i.e. to tell people not what to think, but what to think about as opposed to persuasion or attitude change. Agenda setting is usually referred to as a function of mass media and not a theory (McCombs & Shaw, 1972).