 we must be prepared to accept the possibility that what we call “the environment” may lie, in part, within the skin of the biological organisms. That is, some of the constraints that must be taken as givens in an optimization problem may be physiological and psychological limitations of the organism (biologically defined) itself. For example, the maximum speed at which an organism can move establishes a boundary on the set of its available behavior alternatives. Similarly, limits on computational capacity may be important constraints entering into the definition of rational choice under particular circumstances. (Simon 1955a: 101)