The study tried to answer how well experiment measures for other-regarding behavior could generalize real behavior or enable it to be called “the external validity”. The results of the three experiments were combined as proxies of other-regarding behavior and actual collective behavior of villagers in coastal conservation activities. The Kok Kham sub-district in Samut Sakorn province served as the study site because villagers here have acted collectively to conserve the coastal area. Results of the three experiments were not significantly correlated with actual collective actions, and answers to survey questions on attitudinal trust and past behavior trust did not appear to predict participation rates for actual contribution. These results suggest that the context-free standard game as manifested in the three experiments used may not be able to generalize cooperative behavior in real life.