Multiple motives of pro-social behavior: evidence from the solidarity game

The article analyses experimental "solidarity games" with two benefactors and one beneficiary. Depending on their motive for giving-e.g., warm glow, altruism, or guilt-the benefactors' response functions are either constant, decreasing, or increasing. If motives interact, or if envy is a concern, then more complex (unimodal) shapes may emerge. Controlling for random utility perturbations, we determine which and how many motives affect individual decision making. The main findings are that the motives of about 75% of the subjects can be identified fairly sharply, that all of the motives discussed in the literature co-exist in the population, and that for any given individual no more than two motives (out of six motives considered overall) are identified. We conclude that a unifying motive for solidarity cannot be derived even when we allow for individually heterogeneous parameterization: different subjects give for different reasons and all existing social preference theories are partially correct.