Myopic reactivity in repeated-choice: The case of competing with others for a scarce, unevenly distributed resource.

Foraging for a scarce resource takes place when fewer resource-units than agents are distributed among several locations and agents choose at which location to look for the resource. But how do foragers distribute themselves over the different locations? Optimal foraging theory postulates that the distribution of agents should match the distribution of resource units (ideal free distribution [IFD]), but research with animals and humans has revealed undermatching at the location at which the resource is most abundant. For the IFD to be reached, full information about other foragers' choices and outcomes is required, information that is usually not available. We conducted a theoretical analysis of the implications of relying on different levels of information: on the incomplete, but still valid information usually available in foraging scenarios and on full information. The analysis demonstrates that myopic reactivity to disappointment, or to regret, which are likely to arise in the wake of incomplete information, leads to undermatching, with either affect leading to different degrees of undermatching. Importantly, these analyses indicate that behavior would be sensitive not only to resource distribution (as in IFD), but also to its overall abundance. Three experiments employing incentivized repeated choices were conducted. The information provided to participants, the number of locations, and resource abundance were manipulated to test the predictions of the models. Analyses of aggregate choice probabilities and trial-to-trial choice dynamics indicate that myopic reactivity to regret provides the best explanation for the observed data. With more information available, behavior matches more closely the IFD predictions.