We show that for many classes of symmetric two-player games, the simple decision rule “imitate-if-better” can hardly be beaten by any strategy. We provide necessary and sufficient conditions for imitation to be unbeatable in the sense that there is no strategy that can exploit imitation as a...

Providing incentives to subjects in internet experiments can be tricky. One simple method is a high score (as in computer games). We test whether high scores provide adequate incentives in comparison to the usual performance based incentives. We find significant differences.

We characterize the class of symmetric two-player games in which tit-for-tat cannot be beaten even by very sophisticated opponents in a repeated game. It turns out to be the class of exact potential games. More generally, there is a class of simple imitation rules that includes tit-for-tat but...

Sick pay is a common provision in most labor contracts. This paper employs an experimental gift exchange environment to explore two related questions using both managers and undergraduates as subjects. First, do workers reciprocate generous sick pay with higher effort? Second, do firms benefit...

The question whether a minimum rate of sick pay should be mandated is much debated. We study the effects of this kind of intervention with student subjects in an experimental laboratory setting rich enough to allow for moral hazard, adverse selection, and crowding out of good intentions. Both...