Positional Order and Group Size Effects in Resource Dilemmas with Uncertain Resources

We report the results of three experiments in which groups of players share a common resource pool whose size is a random variable with a commonly known distribution. We study a new information structure - called the positional order protocol - under which requests are made in an exogenously determined and commonly known order without disclosing the requests of previous players in the sequence. Mean individual requests under this protocol of play are compared with data gathered under the more familiar simultaneous protocol (simultaneously made requests) and sequential protocol (sequentially made requests with full disclosure of previous requests). Previously reported effects of the resource uncertainty on individual requests obtained under the simultaneous and sequential protocols are generalized across different group sizes. In contrast to the game-theoretical prediction, which does not distinguish between the simultaneous and positional order protocols, mean individual requests and position in the sequence are highly and significantly correlated. We conclude that position effects can be induced by temporal priority, even in the absence of differential information.