9515344 Scholz Why do citizens obey democratic laws? Consider, for example tax laws to collect money for desired public goods or environmental laws to minimize widely-recognized public bads. Obedience would leave everyone better off, but the temptation to free ride and shirk citizenship duties makes obedience an uncertain proposition. Is Hobbesian deterrence essential to gain compliance, or can social cooperation support compliance with laws designed to resolve collective action problems? Scholz's prior NSF research suggests that compliance behavior can only partly be explained by deterrence, and that a theory of cooperation in collective action situations is needed to understand obedience with democratic laws. His proposed "trust heuristic" explains cooperation in terms of trust in government, trust in other citizens, and other civic attitudes that reflect the positive and negative experiences the citizen has with the cooperative. Tm the extent that the individual's likelihood of cooperation increases as attitudes become more positive toward the collective, these attitudinal heuristics replicate the "nice, retaliatory, yet forgiving" characteristics associated with robust cooperative strategies in prisoners dilemma games, and hence may provide the basis for social cooperation. The trust heuristic represents "social capital" which dramatically increases the ability of weak enforcement agencies to maintain compliance (cooperation) with laws resolving collective action problems. To further develop and test this hypothesis and also to provide a more solid foundation for the theory of cooperation in large-scale collective action settings, the current research: 1) extends existing results based on 2-person, full information prisoners dilemma games to investigate the generic properties of robust strategies capable of supporting cooperative solutions to n- person collective action problems. 2) utilizes laboratory experiments to test the correspondence bet ween formal strategies and heuristics used by human subjects in collective action settings. The research integrates the diverse approaches of five productive researchers essential for tackling the challenging problem of cooperation in large-scale collective action settings. The combined methodology can be applied to numerous other collective action problems and should be of great interest to a variety of social science researchers. ***