Overharvesting of resources of unknown size

Artikel i vetenskaplig tidskrift, 1999

In two resource-dilemma experiments participants were free to request an amount from an available resource whose size was a random variable with a uniform distribution either within a small interval (low resource uncertainty) or within a large interval (high resource uncertainty). In Experiment 1, one group of 20 undergraduates guessed the size of the resource as well as rated how confident they were. In three other groups equal numbers of undergraduates requested an amount which they would receive if it did not exceed the available resource. In one of these groups the outcome was only dependent on resource size, whereas in the remaining groups the outcome also depended on the requests by four other unfamiliar subjects who were either real or imaginary. Partially supporting a perceptual-bias explanation, subjects were in all groups found to overestimate or overharvest when resource uncertainty increased. Yet, an optimism or outcome-desirability bias explanation was maintained since the requests increased more with resource uncertainty than did the guesses whether or not the outcome depended on otherś requests. Experiment 2 employed another three groups of 20 undergraduates in a step-level resource-dilemma. Confirming the conclusion of Experiment 1, the results supported the outcome-desirability bias explanation but failed to support an egoism-bias explanation in showing that the overharvesting effect of resource uncertainty was not affected by social uncertainty.