Peter Wason

Who they are

Wason is a psychologist whose 1960 paper is the work this site cites. The record used here is the paper's abstract and bibliographic details, and no biographical material has been verified, so this page does not give his dates, positions or institutions.

Key papers

• Wason, P. C. (1960). On the failure to eliminate hypotheses in a conceptual task. Quarterly Journal of Experimental Psychology, 12(3), 129-140. doi:10.1080/17470216008416717

Key ideas

The paper contrasts two ways of testing an idea. In the enumerative route a person collects instances that agree with the hypothesis. In the eliminative route a person also looks for instances that would rule it out. Wason designed a number-rule task in which the correct rule was implied by many more obvious rules and the possible instances were unlimited, so that the first route would tend to produce wrong conclusions.

Of 29 participants, 6 reached the correct conclusion without first reaching an incorrect one, 13 reached one incorrect conclusion, 9 reached two or more, and 1 reached none. Wason concluded that those with two or more incorrect conclusions were unable or unwilling to test their hypotheses, and he discussed the implications for scientific thinking. The task is described on this site under The 2-4-6 Task, and the wider procedure under Confirmatory Hypothesis Testing.

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