Self-selection into laboratory experiments: pro-social motives versus monetary incentives
通过改变招募邮件内容，研究金钱激励和助研呼吁对实验参与者自我选择的影响，发现不提金钱奖励会使报名率下降三分之二，而助研呼吁无效果，且不同招募方式下参与者的亲社会动机无显著差异。
Abstract Laboratory experiments have become a wide-spread tool in economic research. Yet, there is still doubt about how well the results from lab experiments generalize to other settings. In this paper, we investigate the self-selection process of potential subjects into the subject pool. We alter the recruitment email sent to first-year students, either mentioning the monetary reward associated with participation in experiments; or appealing to the importance of helping research; or both. We find that the sign-up rate drops by two-thirds if we do not mention monetary rewards. Appealing to subjects’ willingness to help research has no effect on sign-up. We then invite the so-recruited subjects to the laboratory to measure their pro-social and approval motivations using incentivized experiments. We do not find any differences between the groups, suggesting that neither adding an appeal to help research, nor mentioning monetary incentives affects the level of social preferences and approval seeking of experimental subjects.