Raising "lab rats"

Experimental subjects usually self-select to the laboratory and this may introduce a bias to the derived conclusions. We analyze data stored by a subject-pool management software at an experimental laboratory and speculate about the e ect of individual decisions on returning. In particular, we test whether experience and earnings in previous sessions together with demographic variables explain the decision to return to the laboratory. We nd that males and (in monetary terms) well-performing subjects are more likely to participate again in experiments.