Conditions and motives for voluntary sharing. Results of a solidarity game experiment

This paper studies experimentally the conditions and motives for voluntary solidarity, following a game theoretical approach. The ‘solidarity game’ that is used in this study consists of groups of four players and is based on the solidarity game of Selten and Ockenfels (1998). In each group, two winners, which are either randomly selected or on the basis of their performance on a quiz, distribute 20 credits each (reflecting real money). We tested four hypotheses regarding the effect of various conditions on voluntary sharing, related to the motives for solidary behaviour, viz. self-interest, fairness, neediness and meritocracy. For most of our hypotheses the experiments provided support, although there are a few exceptions.
Players share more with others in the first round of the four shots game than in the one shot game, but their gifts decrease quickly as the game progresses, which confirms that they act largely out of self-interest. Players give more to a player from whom they have received money in the previous rounds (fairness, resulting in direct reciprocity). However, players do not give more to co-players who have been generous to others in the previous round, which would have been proof of indirect reciprocity. Players do not give more to a loser than to a winner in the current round, and, consequently, do not equalize the differences in revenue. However, they give more to players who have received relatively little in previous rounds, which suggests that neediness of the potential beneficiary is also a motive. Finally, winners give more in the random based conditions, when they do not really ‘deserve’ to be a winner, than in the performance based conditions, which offers support for the meritocracy hypothesis.
The motives that the subjects expressed themselves for their sharing behaviour in answering some post-hoc questions, mirrors their actual behaviour pretty well. Additionally, we also analyse the effect of some personal characteristics, and the party preferences and media use of the players.