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.

Chapter 10 summarizes the book’s principles and discusses future research directions.

Chapter 7 differentiates processes of attitude formation and change, with special attention to the influence of prior attitudes on the decision to seek out a persuasive message and the ultimate impact of a message or behavioral intervention, particularly in combination with goals of action and inaction. The key elements of persuasive communications and interventions to change behavior include behavioral recommendations, persuasive arguments, the communicator, and affective feelings. Message actionability is discussed in the context to concept priming, numbers of recommendations including in a message or intervention, and other factors. These elements and the processes leading to behavior are discussed.

Chapter 1 presents the objectives of the book, which blends a traditional monograph with topics of contemporary interest and an analysis of attitude and behavior change in real and virtual contexts. Definitions and a overview of the theory are presented.

Chapter 8 describes how prior attitudes shape the processing of persuasive messages and behavioral interventions in fundamental ways. First, people select messages and interventions in ways that minimize their likely impact. They seek pro-violence messages when they already espouse pro-violence beliefs and healthy eating messages when they already follow healthy diets. These decisions, of course, decrease the probability of changing attitudes and behaviors that have negative social and health effects, which has led to my research on finding methods to decrease selective exposure biases. For example, because selective exposure is often tied to a low sense of one’s ability to self-defend if one’s attitudes or behaviors come under attack, reassuring an audience that they will only change if they want to is often sufficient to increase exposure to messages and enrollment in behavioral interventions. In addition, understanding attitude and behavior change requires understanding activation of prior attitudes and other information contained in the message. For example, easy-to-access prior attitudes generally decrease change in response to new information but may also increase change when they facilitate comparison with new information. Furthermore, when people who are called to report an attitude retrieve the initial basis for their attitude, the structure of that information in memory drives the degree of attitude change in that situation. Different sleeper effects illustrate such effects of the initial representations of the information contained in a persuasive message.

Chapter 9 discusses how messages designed with the intent of influencing behavior and behavioral interventions are successful when they influence factors in the person and the situation that ultimately make those programs actionable. Actionability is the probability that the message or intervention communicates or enables performance of behavioral recommendations . First, a message or behavioral intervention can stimulate the cognitive, motivational, or behavioral processes that ultimately make the individual perform the recommended behavior. Second, it can promote behavioral recommendations that fit within the world in which potential actors live. These factors and relevant data are discussed.