Experiment timing and preferences for fairness

Classroom experiments examining fairness preferences [Andreoni, J., Miller, J., 2002. Giving according to GARP: an experimental test of the consistency of preferences for Altruism. Econometrica 70 (2), 737-753] were conducted to examine two issues: first, are classroom points a salient reward medium (comparable to cash in research experiments)? Secondly, does experiment timing during the semester influence results. Subject choices are consistent with the existence of well-behaved utility functions, indicating that points experiments can be valid. Secondly, subjects are more likely to be "selfish" when the experiment is conducted early rather than late in the academic semester. This result has behavioral implications for environments where nonmonetary incentives prevail, as well as implications for the growing number of instructors using experiments and follow-up discussion in the classroom.