Cooperation in public goods dilemas: group size as contribution signal

Abstract

In a simulated public goods dilemma, framed as “saving” and “invest” games, 26 undergraduate students were instructed to play themselves, but in fact they interacted with a computer. Each subject participated once in a series of 45 independent single-trial dilemmas. On each trial participants received an endowment of five points to decide whether or not to contribute it for the provision of a public good. In order to evaluate the effects of group size to determine how much subjects contribute, they received information indicating that their group was relatively cooperative (80%) with a provision point of 24 units. A significant effect of group size was found, with participants in the small group condition emitting more cooperative responses. Findings suggest that the effect depends on the particular sequence of experimental phases. Results lend some support to the conditional cooperation explanation. Our central focus was on the two dimensions of response available to subjects: adjustments in their individual contribution, and willingness to gain control of the interchange. The observed differences and the regulation factors of group size are discussed.