Jan Stoop's research is concerned with the measurement of social preferences of humans. He does 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, Jan Stoop conducts 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, he studies how to design optimal labour contracts: 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.