Misinterpretation of conditional statements in Wason's selection task

Errors may be made on Wason's selection task because either (a) the rule to be tested is misunderstood, or (b) reasoning from that rule is inaccurate, or both. We report two experiments using the experimental paradigm introdu ced by Gebauer and Laming in which subjects are given six problems in succe ssion. We use the subset of cards selected by each subject as (a) an indica tion of how the rule is understood and, when that selection is consistent t hroughout all six problems (so that we can infer a consistent understanding of the rule), as (b) a basis for evaluating the accuracy of the subject's reasoning according to three independent criteria. Experiment 1 adds an exa ctly parallel contextual version of the task to permit comparison between p erformances (by the same subjects) on the two versions. Experiment 2 repeat s Exp. i, but with negatives inserted in the conditional rule. Most subject s make a consistent selection of cards throughout all six problems, but typ ically appear to misunderstand the rule. This is so in both abstract and co ntextual tasks and replicates the finding by Gebauer and Laming. Most misun derstandings consisted of either (a) reading the simple conditional rule as a bi-conditional or (b) substituting "top/underneath" for "one side/other side". In Exp. 1 subjects seldom misevaluated the rule they appeared to be testing, but such "errors" of evaluation were common in Exp. 2. Negatives c onfuse the subjects and should not be used in any conditional application t hat matters. In Exp. 2 (but not If there was a significant correlation betw een interpretations of the two tasks. We provide an explanation of "matchin g bias" tit results from the confluence of the two common misunderstandings above) and comment on "mental models" which are, at present, unable to acc ommodate the variety of results we present here. We also relate our experim ental paradigm to the conditional inference task and to truth tables.