I investigate the effects of strategic, social and confused motivations in experiments on the voluntary contribution mechanism in the provision of a public good with three treatments: the matching method (partners vs. strangers), the payoff table (detailed vs. rough) and the other's payoff information (known vs. unknown). The results show, first, that subjects in the partners treatment invest significantly more in public goods than subjects in the strangers treatment, regardless of the treatments of payoff table and payoff information. Second, only in the partners treatment, subjects with the rough table invest significantly more in public goods than subjects with detailed table. Third, only in partners treatment, subjects in the known treatment invest significantly more in public goods than subjects in the unknown treatment. These results suggest that subjects decided investment levels based on strategic motivation.
