Similarity and choice.

This article examined choices between alternatives when the options confronting the decision maker have similar levels on an attribute. In these situations, 2 empirical phenomena often occur. First, differences on other attributes are enhanced. Similarity along 1 attribute magnifies differences on others. Second, violations of strong stochastic transitivity often occur. A contrast-weighting theory of choice is presented that can account for these puzzling phenomena. Binary choices are represented as a monotonic function of the difference between the utilities of the options. Furthermore, the utilities of any given attribute are weighted according to the similarity of the levels along the other attribute. Small contrasts along 1 dimension result in greater weight for the other dimension. This contrast-weighting theory is consistent with empirical results in several domains, including psychophysics, social judgement, and risky decision making