Foundations Of Cognitive Science

Deductive Inference

Inferences are made when a person (or machine) goes beyond available evidence to form a conclusion (Johnson-Laird, 1993). With a deductive inference, this conclusion always follows the stated premises. In other words, if the premises are true, then the conclusion is valid. Studies of human efficiency in deductive inference involves conditional reasoning problems which follow the "if A, then B" format.

The task of making deductions consists of three stages. First, a person must understand the meaning of the premises. Next they must be able to formulate a valid conclusion. Thirdly, a person should evaluate their conclusion to tests its validity.

The study of deductive inference originally was important with respect to human rationality; errors in deductive reasoning were seen as challenges to the logicism of classical cognitive science (Oaksford & Chater, 1998; Wason, 1966). More recently, researchers have used modern imaging techniques to explore the areas of the brain that might be involved in deductive inference (e.g. Goel et al., 1997; Wharton & Grafman, 1998).


  1. Goel, V., Gold, B., Kapur, S., & Houle, S. (1997). The seats of reason? An imaging study of deductive and inductive reasoning. Neuroreport, 8, 1305-1310.
  2. Johnson-Laird, P. N. (1993). Human and machine thinking. Hillsdale, NJ : Lawrence Erlbaum Associates.
  3. Oaksford, M., & Chater, N. (1998). Rationality In An Uncertain World: Essays On The Cognitive Science Of Human Reasoning. Hove, East Sussex, UK: Psychology Press.
  4. Wason, P. C. (1966). Reasoning. New York: Penguin.
  5. Wharton, C. M., & Grafman, J. (1998). Deductive reasoning and the brain. Trends in Cognitive Sciences, 2(2), 54-59

(Revised March 2010)