My research is concerned with the measurement of social preferences of humans. I do this by means of lab experiments where (usually) students are playing a game behind a computer. These games gather insights into the social preferences of the participants. Besides lab experiments, I conduct field experiments in a 'natural environment', with non-student participants. The insights gathered from these experiments show to what degree the social preferences measured in the lab carry over the the real world. Besides research on social preferences, I study how to design optimal labour contracts. This means that we study when employees exert most effort for their boss. One can think of a contract which pays on a per-unit base, or a scheme in which only the most productive employee receives money. The way in which I study these incentives is by means of lab experiments and field experiments.