Two modern developments in matching theory.

Matching theory is a mathematical theory of choice behavior, parts of which have been shown to hold in natural human environments and to have important therapeutic applications. Two modern developments in matching theory are discussed in this article. The first is the mathematical description of behavior in asymmetrical choice situations, which are situations where different reinforcers and/or different behaviors are associated with concurrently available response alternatives. Most choice situations in natural human environments are probably asymmetrical. The second development in matching theory is the mathematical description of a tendency toward indifferent responding in all choice situations. Behavior in asymmetrical choice situations and the tendency toward indifferent responding in all choice situations can be described by modifications of the matching equations, which change the equations from lines into power functions. These modern forms have been extraordinarily successful in describing behavior in choice situations, and are the forms most likely to accurately describe human behavior in naturally occurring environments.