Many scholars have stressed the importance of membership in associations as one of the main determinants of inter-personal trust (e.g. Zucker, 1986; Coleman, 1990; Lahno, 1995). In particular, Olson (1982) and Putnam et al. (1993) provided two different accounts of the role of private voluntary associations in affecting propensity to trust. Olson emphasized the tendency of some groups to pursue private interests and lobby for preferential policies. From this point of view, associations do not contribute to create a social fabric of trust, but instead increase divisions. By contrast, Putnam et al. (1993: 88) stated that voluntary associations Òinstill in their members habits of cooperation, solidarity and public-spiritednessÓ. We carried out an experimental analysis aimed at investigating the propensity to cooperate of voluntary members of different kinds of associations compared with propensity to cooperate of people who have never been voluntary members. Association members came from typically ÒOlsonianÓ association Ð i.e. trade unions Ð and typically ÒPutnamianÓ associations Ð i.e. cultural and social welfare or health associations. Our experimental design is based on a standard Investment Game (Berg et al. 1995). It comprises an in-group treatment, where members interact with other members of their own association, and an out-group treatment, in which members are paired with people from the general population. All interactions are anonymous. To the best of our knowledge, the present study represents the first attempt to investigate the relationship between voluntary participation in different kinds of associations and propensity to cooperate by involving people of different age, education and socio-economic status (previous contributions focused on samples of college students: Glaeser et al. 2000, Anderson et al. 2004). Our preliminary evidence shows that: ¥ Voluntary members of associations contribute significantly more (around 50%) than non- members, both in the in-group and in the out-group treatment; this is a much higher proportion than what found by Ruffle and Sosis (2006) and Hargreaves-Heap and Zizzo (2009), who on the contrary found no significant difference; ¥ The type of associations of which people are members affects the patterns of cooperation. We find in-group favoritism for members of Olson-type associations, i.e. they cooperate significantly more with their fellow members than with people from the general public. No in-group favoritism is found for Putnam-type associations members. Moreover, Putnam- type associates cooperate significantly more than non-members with people from the general public, while members of Olson-type associations contribute as non-members when paired with people from the general public. These results seem to confirm the original intuition of the two authors.
