Undermatching is an emergent property of selection by consequences.

A computational theory of selection by consequences [McDowell, J.J, 2004. A computational model of selection by consequences. J. Exp. Anal. Behav. 81, 297-317] was tested by studying the responding of virtual organisms that were animated by the theory on random interval schedules of reinforcement. The theory generated responding by applying principles of selection, reproduction, and mutation to a population of potential behaviors that evolved in response to the selection pressure exerted by reinforcement. The organisms' equilibrium response rates were well described by the modern version of the Herrnstein hyperbola, which includes an exponent on reinforcement rate. Under strong selection pressure this exponent decreased with increasing mutation rate from a value near 1.0 at 1% mutation to an asymptotic value of 0.83 at mutation rates of 10% and greater. This asymptotic value is consistent with values obtained by fitting the equation to data from live organisms responding on single schedules, and with the value of about 0.80 that is expected on the basis of extensive research with live organisms responding on concurrent schedules. These results show that the computational theory is consistent with the modern theory of matching [McDowell, J.J, 2005. On the classic and modern theories of matching. J. Exp. Anal. Behav. 84, 111-127], and that it is a viable candidate for a mathematical dynamics of behavior.