On the failure to eliminate hypotheses in a conceptual task
Wason asked whether intelligent young adults test a hypothesis only by collecting instances that agree with it or also by seeking instances that would rule it out. The rule-discovery task was built so that the correct rule was implied by many more obvious rules and the set of possible instances was unlimited, so confirming-only reasoning was likely to give wrong conclusions. Of 29 participants, 6 reached the correct rule 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 discussed implications for scientific thinking.
Wason asked whether intelligent young adults test a hypothesis only by collecting instances that agree with it or also by seeking instances that would rule it out. The rule-discovery task was built so that the correct rule was implied by many more obvious rules and the set of possible instances was unlimited, so confirming-only reasoning was likely to give wrong conclusions. Of 29 participants, 6 reached the correct rule 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 discussed implications for scientific thinking.
Written from the abstract, journal record via scilit, 2026-10-31.
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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 https://doi.org/10.1080/17470216008416717