Rational Hypothesis-Testing Strategies in a Rule Discovery Task

Abstract

In Wason’s (1960) inductive learning task, subjects must discover a rule that governs the production of sequences of three numbers, such as ‘2-4-6’, by generating new triples that receive feedback. Data obtained with Wason’s original procedure suggest that people test few hypotheses before announcing their guess and mostly proceed on the basis of a positive-test strategy. These features are commonly regarded as lamentable aspects of reasoning agents who fail to appreciate normative models of hypothesis-testing. Such interpretations, however, are relative to the inferential context in which the behavior is observed. In the present study, Wason’s original procedure was modified such that in one condition desirable consequences were associated with the production of positive exemplars and undesirable consequences with negative exemplars. In a second condition, the consequences were reversed. Subjects in the latter condition produced more exemplars, of a greater variety, and were more likely to discover the rule than subjects in the first condition. It seems then that in this second condition the hypothesis-testing strategy emerging from the subjects’ appreciation of the cost and benefit of generating certain kinds of triples coincided with the normative strategy. However, since subjects in both conditions aimed to achieve different goals their hypothesis-testing strategies can, in that respect, be characterized as rational.