Group choice and individual choices: modeling human social behavior with the Ideal Free Distribution.

Group choice describes the behavioral phenomenon in which a group of individuals chooses between two behavioral alternatives over time and the Ideal Free Distribution (IFD) [Acta Biotheor. 19 (1970) 16] describes group choice analogous to individual choice and the matching law. Our experiments investigated the usefulness of IFD analyses of human group choice based on a procedure reported in Sokolowski et al. [Psych. Bull. Rev. 6 (1999) 157]. A group of humans distributed into two subgroups to receive points that could earn cash prizes. The participants aligned themselves into subgroups by choosing between two rows of chairs, two different colored cards, or two cyber-subgroups. Different methods of distributing points to participants showed that IFD matching was dependent on the method (i.e. sharing points evenly produced near IFD matching, but probabilistic point distribution produced more undermatching). In addition, the sensitivity measures of individual choices in the groups differed from the sensitivity of the groups' choices.