An experimental test of the ideal free distribution in humans

The effects of reinforcer magnitude and group size

Abstract

The ideal free distribution (IFD) theory describes how animals living in the wild distribute themselves between two different resource sites. The IFD theory predicts that the ratio of animals in the two resource sites is equal to the ratio of resources available in those sites. The present study investigated the effects of absolute reinforcer magnitude and group size on the distribution of humans between two resource sites. Two groups of undergraduate students (N=10 and N=20) chose blue or red cards to earn points. The ratio of points assigned to each color varied from 1:1 to 4:1 across five conditions. In each condition, absolute reinforcer magnitude was varied. The generalized ideal free distribution equation was fit to the data obtained under the different magnitude and group size conditions. These results suggest that larger absolute reinforcer magnitude and smaller group size produce higher sensitivity to resource distribution.