Social norms and cooperation in real-life social dilemmas

The hypothesis, that injunctive and descriptive norms interact positively or synergistically to promote cooperation in social dilemmas, is tested in the context of a survey study focusing on environmentally responsible behaviour. Measurement error and strong and positive correlations between the two types of normative beliefs make it difficult to test the interaction hypothesis. By using structural equation modelling with residual centering, these problems are overcome and the interaction hypothesis is confirmed. The result is stable across three replications spanning a two-year period.