Effort is not a monotonic function of skills: Results from a global mobile experiment

At the core of economic theory is the monotonicity hypothesis: an agent's effort, as a function of their skills, is either non-decreasing or non-increasing, but not both. To test this hypothesis, we use data from Blues and Reds, a mobile app designed to conduct economic experiments that consists of a series of interactive puzzles. The sample includes 6,463 subjects from 141 countries. We measure subjects’ skills and effort levels using their response times. We replicate the same test 22 times. Surprisingly, each time we find that the optimal effort is not a monotonic function of skills but rather has a U-shape contradicting the monotonicity hypothesis.