Incentivizing participation with full completion: The Power of self-selected rewards

The attrition problem is a common challenge in longitudinal studies. We explore payment mechanisms aimed at increasing the number of participants who complete all tasks. Specifically, we investigate the impact of empowering participants with the option to self-select between a piece rate payment method, rewarding each task completed, and an all-or-nothing payment method, which grants full payment only if all assigned tasks are finished. Data from two longitudinal studies shows that the self-select payment mechanism attracts more participants to sign up. Importantly, participants are willing to choose the all-or-nothing incentive when given a choice and subsequently achieve a higher rate of completing all tasks compared to those who are randomly assigned to a payment method. Nonetheless, the higher completion rate is accompanied by a trade-off: the quality of task completion diminishes when participants select the all-or-nothing scheme. Our findings suggest that offering the all-or-nothing incentive as an option can effectively achieve a higher rate of full completion provided that adequate quality control measures are in place.