An evolutionary theory of behavior dynamics applied to concurrent ratio schedules.

An evolutionary theory of adaptive behavior dynamics was tested by studying the behavior of artificial organisms (AOs) animated by the theory, working on concurrent ratio schedules with unequal and equal ratios in the components. The evolutionary theory implements Darwinian rules of selection, reproduction, and mutation in the form of a genetic algorithm that causes a population of potential behaviors to evolve under the selection pressure of consequences from the environment. On concurrent ratio schedules with unequal ratios in the components, the AOs tended to respond exclusively on the component with the smaller ratio, provided that ratio was not too large and the difference between the ratios was not too small. On concurrent ratio schedules with equal ratios in the components, the AOs tended to respond exclusively on one component, provided the equal ratios were not too large. In addition, the AOs' preference on the latter schedules adjusted rapidly when the equal ratios were changed between conditions, but their steady-state preference was a continuous function of the value of the equal ratios. Most of these outcomes are consistent with the results of experiments with live organisms, and consequently support the evolutionary theory.