ABSTRACT
This chapter aims to give the reader some context for the current wave of field experiments in political science and public policy. It explains how trials have grown in importance over time and gives a sense of how their use has disseminated across the social sciences. This chapter also offers a broader perspective for the case studies presented in later chapters. There is a wider purpose too. Although the history of the use of experiments appears like the long march of the progress of truth, the diffusion of the gold standard, in fact, their development outside medical practice has been relatively slow, a gradual and patchy set of adoptions rather than the avalanche that might have been expected. The chapter discusses different explanations for the diffusion of experiments, but it also focuses on their practical dimensions and why they are hard to do. This feature of experiments partly explains their slow diffusion, as well as the difficulty of transferring knowledge about how to do them, particularly across disciplines whose members do not have a great contact with each other.
