On “lab rats”

► Self selection of subjects into experiments might introduce a bias to experimental results. ► We study the effect of individual decisions on returning to the lab. ► We find that males and well performing subjects are more willing to participate again. Experimental subjects usually self-select to the laboratory and this may introduce a bias to the conclusions derived from observing their behavior. We analyze data stored by a subject-pool management program at an experimental laboratory and speculate about the effect of individual decisions on returning. Specifically, we test whether experience and earnings in previous sessions together with demographic variables explain the decision to return to the laboratory. We find that males and (in monetary terms) well-performing subjects are more likely to participate in experiments again.