This thesis contains three chapters studying questions of behavioural and experimental economics. Chapter 1, titled “Heterogeneity in lies and lying preferences”, develops a theoretical framework and an experimental design which I use to identify systematic patterns of lying behaviour in the presence of heterogeneity of lies and decision-makers. I show that accounting for these patterns provides large gains in out-of-sample predictions of lying decisions. Chapter 2, titled “Eliciting preferences for truth-telling in a sample of politicians”, studies the connection between politicians’ truth-telling preferences and observable variables such as re-election success. The chapter has been published in the Proceedings of the National A...