Gigerenzer’s eclectic normativism

Aslı Selim

This thesis examines Gigerenzer’s criticism of classical rationality and evaluates the adequacy of the ecological rationality view that he offers in its place. Classical rationality assumes that normative standards are determined by formal logic, probability theory, and decision theory. Several studies have demonstrated that people usually fail to conform to the norms of classical rationality and concluded that people are subject to various cognitive biases and fallacies. Gigerenzer rejects this view, claiming that classical rationality is not suitable for the study of human reasoning. First, I analyze Gigerenzer's criticism of the cognitive fallacy studies and the normative benchmarks of classical rationality. I argue that rational norms need not be descriptively correct and that formal logic, probability theory and decision theory should be retained as the normative benchmarks of rationality. Secondly, I discuss Gigerenzer’s ecological rationality view, in which it is assumed that instead of formal logic, probability theory, and decision theory, psychologically plausible heuristics can be used for describing human reasoning and prescribing rational norms. I argue that the heuristics that have been proven to be effective and are suitable for prescription are not psychologically plausible and the ones that are psychologically plausible do not perform well consistently enough to be suitable for prescriptive purposes. I conclude that the study of psychologically plausible heuristics should be confined to the description of human behaviour and that the heuristics that are suitable for prescription need not be psychologically plausible.