Human Reasoning and Reasoning Systems
Almost up to the close of the nineteenth century and until the work of Darwin ( 1872) and Spencer ( 1896), psychology was undifferentiated from philosophy. Rational man was held to think essentially in terms of the philosopher's logical calculus ( Whitehead and Russell 1910- 1913). Man was perceived as obeying inevitably the laws of logical thought.
The work of Darwin, especially the Descent of Man ( 1871), placed the psychology of thought in the general framework of evolution, survival, and environmental adaptation. In fact, in Descent of Man Darwin outlined a number of experimental designs intended to test the problem-solving or reasoning ability of animals. This opened a way to a long series of experiments in comparative psychology in which reasoning for a time came to be associated with the behavior of lower animals, including the rat ( Heron and Hunter, 1922).
But man's rationality was dethroned not only through Darwinian evolutionary perspectives but also through the work of Freud. In his "Doctrine of Psychosexual Evolutionism" ( 1935), he forever reduced man's everyday behavior and mishaps to primitive and irrational motives and conflicts, a concept he elaborated in his Psychopathology of Everyday Life ( Freud, 1966). Moreover, the Freudian view seemed to hold that the very rationality of man could sometimes be attributed to intellectual avoidances and defenses, sometimes with clear obsessional or compulsive symptoms ( Fenichel, 1945). The early laboratory investigations of human reasoning ability and performance seemed to separate psychology as a science from its maternal source in