What is public opinion, what factors cause it to form in particular ways, and why does it matter? In this chapter, we define public opinion as opinions on matters of public debate that have significant implications for society. Then, we provide an overview of key developments in three central topics in research on public opinion. First, we discuss research on opinionation, or when and why a person forms an opinion on a political topic. Second, we discuss directionality of opinion, or factors that shape whether a person forms a particular kind of opinion (e.g., favourable or unfavourable) on an issue. Finally, we discuss the consequences of public opinion, or how opinions shape action, with a focus how public opinion influences voting, civic activism, and government attention and action. We end by considering emerging research trends in the field of public opinion that can inspire future research on the topic.

During the last thirty years or so, political psychologists have turned out a great deal of empirical research and theory of which we can be quite proud. In the midst of this productive enterprise, we have occasionally taken time out to lobby other scholars outside our circles to make use of the theories and methods that we find most useful (e.g., Kinder and Palfrey 1993). Less often, we have taken a step back from our empirical work to don a self-critical hat and ask whether we are going about our enterprise in as constructive a fashion as we might (see, e.g., Kuklinski, Luskin, and Bolland 1991).

One purpose of this book is to do so quite deliberately. Other chapters address the questions of whether political psychology is sufficiently theoretical and whether it is sufficiently political, two matters on which we have been criticized by political scientists who take different approaches. In this chapter, I will address a different question, asking whether political psychology is sufficiently psychological.

My goal is to be controversial in raising philosophical issues about political psychology as an enterprise that may deserve more explicit consideration than they currently receive. In short, I will suggest that two very different sorts of political psychology are being carried on, sometimes within the same research project or even within the same paper.

Political psychology is a relatively young empirical enterprise. As dated by research involving quantitative techniques such as sample surveys and laboratory experiments, political psychology does not begin to approach the long histories of chemistry, physics, and astronomy. And even considering the application of typically qualitative analytic methods such as case studies and historical document analysis, our enterprise is in its relative youth (see, e.g., Hermann 1986).

Partly as a result of our youth and partly as a reflection of it, we have not experienced the dramatic paradigm shifts that other sciences have (see, e.g., Kuhn 1970). Whereas other disciplines have seen the rise and fall of major organizing theoretical perspectives, we have shown no signs yet of rejecting old overarching perspectives in favor of new ones. There have also been no dramatic shifts during the history of political psychology in terms of the methods we employ to evaluate our hypotheses empirically. This is not to say that methods are uniformly employed by investigators across the subfield; clearly, this is not the case. But the current state of affairs seems to be one of tolerance of a multiplicity of methods, rather than a universal sense that some methods have proven not to be useful while others are.

Yet a close look at the history of studies in some areas of political psychology suggests that there might be some useful lessons to be learned about the value of certain methods over others.