The effect of instructions on performance in the Wason selection task

Abstract

The effect of instructions on performance on the standard abstract form of Wason's selection task was examined. Instructions to determine whether or not the statement is violated did not lead to an increase in correct responding, contrary to previous suggestions that such instructions would induce falsification strategies, but rather to an increase in verification bias. Instructions to determine whether the statement is true or false led to increased variability in performance, supporting the suggestion that such instructions are inherently ambiguous. Thus, the results demonstrate that the form of instructions can have a significant effect on performance in the selection task. Verification bias did better as an explanation of the data than did matching bias, which only fared well when its predictions coincided with those of verification bias. A substantial proportion of the data was unaccounted for by either of these strategies, which is consistent with the findings of a number of other recent studies.