Experimental Designs for Political Communication Research

Introduction As recently as three decades ago, the use of experimental methods was a rarity in the disciplines of political science, sociology, and communications. Beginning in the early 1980s, a surge of interest in the interdisciplinary field of political psychology set in motion a trickle of experimental methods into several sub-fields of political science, including political communication. But despite the increased interest, longstanding concerns over the artificiality of experimental settings, the unrepresentativeness of experimental subject pools and the questionable generalizability of experimental findings has continued to impede the further diffusion of experimental methods. In this chapter I describe the inherent strengths of the experiment as a basis for causal inference, using recent examples from political communication research. I argue that the technological advances associated with the rapid diffusion of the Internet have already gone a long way toward neutralizing the traditional weaknesses of experimentation. First, experiments administered online can prove just as realistic as conventional experiments. Second, issues of sampling bias-previously endemic to experiments-can be overcome through the greater " reach " of online experiments and, in addition, by the application of standard probability sampling techniques to the recruitment of online experimental participants. These developments significantly alleviate concerns over the generalizability of experimental research and as a result, experiments now represent a dominant methodology for political communication researchers. In the field of political communication, the principal advantage of the experiment over the survey-and the focus of the discussion that follows-is the researcher's ability to isolate and test the effects of specific components of political messages. Consider the case of political campaigns. At the aggregate level, campaigns encompass a concatenation of messages, channels, and sources, all of which may influence the audience, often in inconsistent directions. The researcher's task is to identify specific causal factors and delineate the range of their relevant attributes. Even at the relatively narrow level of campaign advertisements, for instance, there are virtually an infinite number of potential causal factors, both verbal and visual. What was it about the infamous "Willie Horton" advertisement that is thought to have moved so many American voters away from Michael Dukakis during the 1988 presidential campaign? Was it, as widely alleged, Mr. Horton's race? Or was it the violent and brutal nature of his described behavior, the fact that he was a convict, the race of his victim, or something else entirely? Experiments make it possible to isolate the explanation, whether …