Impersonal influence is about how people are affected by their perceptions of the collective opinions or experiences of others--things such as the well-publicized results of opinion polls (in the case of others' opinions), or media's coverage of the collective experiences of others (such as the extent to which others are experiencing financial problems or are being victimized by crimes). Media content is particularly well suited to serving as a credible channel of information about large-scale collective phenomena. Coverage of the collective opinions (in the case of perceptions of social problems such as crime or unemployment) alters people's political attitudes in surprising, yet subtle ways. These kinds of effects have important implications for the quality of public opinion and the accountability of political leaders in a mass mediated democracy.
Impersonal Influence: How Perceptions of Mass Collectives Affect Political Attitudes. Cambridge University Press, 1998.