How game theory - the ultimate theory of rationality - explains irrational behaviour. In Hidden Games, MIT economists Moshe Hoffman and Erez Yoeli find a surprising middle ground between the hyperrationality of classical economics and the hyper-irrationality of behavioural economics. They call it hidden games. Reviving game theory, Hoffman and Yoeli use it to explain our most puzzling behaviour, from the mechanics of Stockholm syndrome and internalised misogyny to why we help strangers and have a sense of fairness.