Perception as substitute trial and error.

variation and natural selection through differential survival provides a general model for the deterministic description of adaptive phenomena. Recently this model has seen increased application to the adaptive phenomena described by psychologists as problem solving or learning. It is the purpose of this paper to suggest the application of the model to a third level, that is to say, to the adaptive behavior demonstrated in carrying out or executing a well-learned habit. Such an application seems to necessitate the conceptualization of sensory and perceptual processes implied