HUMAN GROUP CHOICE: DISCRETE‐TRIAL AND FREE‐OPERANT TESTS OF THE IDEAL FREE DISTRIBUTION

Ideal free distribution theory predicts that foragers will form groups proportional in number to the resources available in alternative resource sites or patches, a phenomenon termed habitat matching. Three experiments tested this prediction with college students in discrete‐trial simulations and a free‐operant simulation. Sensitivity to differences in programmed reinforcement rates was quantified by using the sensitivity parameter of the generalized matching law ( s ). The first experiment, replicating prior published experiments, produced a greater degree of undermatching for the initial choice ( s 5 0.59) compared to final choices ( s 5 0.86). The second experiment, which extended prior findings by allowing only one choice per trial, produced comparable undermatching ( s 5 0.82). The third experiment used free‐operant procedures more typical of laboratory studies of habitat matching with other species and produced the most undermatching ( s 5 0.71). The results of these experiments replicated previous results with human groups, supported predictions of the ideal free distribution, and suggested that undermatching represents a systematic deviation from the ideal free distribution. These results are consistent with a melioration account of individual behavior as the basis for group choice.