Some experimenters may find it surprising to see the issue of incentives relegated to the last chapter of a methodology book. Monetary incentives are at the center of most methodological controversies in experimental economics and have sparked some heated exchanges among practitioners, so one would perhaps expect them to have a more central place in a book like this. The main reason to delay the discussion until now is not that I find the incentives problem uninteresting or unimportant, but that it is a complicated one. It can be tackled properly only once the right conceptual tools are available; given that I provided the tools in the previous chapters, I can now put them to work.

The idea of using monetary rewards sometimes generates hilarity among noneconomists (“These guys pay their subjects to behave like economists would like them to behave!”), whereas the absence of incentives is dismissed by economists equally bluntly (“What can you learn from ‘cheap talk’? Put your money where your mouth is!”). But more importantly, the presence of “adequate” monetary incentives (we shall see what adequate means shortly) has become de facto a prerequisite for publication in economics journals – and, conversely, the lack of incentives is considered a sufficient condition for the rejection of an experimental study. In contrast, social, cognitive, and economic psychologists tend to apply a less rigid policy.