Published as article in: Journal of Economic Methodology, 2010, vol. 17, issue 3, pages 261-275.

Ideally we would like subjects of experiments to be perfect strangers so that the situation they face at the lab is not just part of a long run interaction. Unfortunately, it is not easy to reach those conditions and experimenters try to mitigate any effects from those out-of-the-lab...

Paper was revised on 2009-11-11.-- Published as article in: Rationality and Society (2009), 21(2), 1-24.