Representational Effects in a Rule Discovery Task

In the Wason (1960) rule discovery task reasoners must infer a rule that governs the production of number sequences. The task instructions are designed such that reasoners’ initial hypotheses are invariantly narrower than the correct rule. The inferential challenge lies in discovering the scope of these initial hypotheses. The traditional task departs from realworld hypothesis testing in at least one significant respect: The task is never presented in a manner that offers a rich external representation of the problem. The study reported here examined representational effects by developing task isomorphs which offered either an external, physically manipulable, representation of the problem space or a graphical presentation of the simple linear relationships between adjacent numbers in a sequence. Compared to a control condition, these task isomorphs lead to a significantly higher incidence of successful rule discovery, and encouraged the creation of a significantly more heterogeneous set of number sequences. Further, control participants had to produce 50% more number sequences than participants who worked with a rich external representation before discovering the rule.