The suppression of q card selections: Evidence for deductive inference in Wason's Selection Task

The results of three experiments investigating the role of deductive infere nce in Wason's selection task are reported. In Experiment 1, participants r eceived either a standard one-rule problem or a task containing a second ru le, which specified an alternative antecedent. Both groups of participants were asked to select those cards that they considered were necessary to tes t whether the rule common to both problems was true or false. The results s howed a significant suppression of q card selections in the two-rule condit ion. In addition there was weak evidence for both decreased p selection and increased not-q selection. In Experiment 2 we again manipulated number of rules and found suppression of q card selections only. Finally, in Experime nt 3 we compared one- and two-rule conditions with a two-rule condition whe re the second rule specified two alternative antecedents in the form of a d isjunction. The q card selections were suppressed in both of the two-rule c onditions but there was no effect of whether the second rule contained one or two alternative antecedents. We argue that our results support the claim that people make inferences about the unseen side of the cards when engagi ng with the indicative selection task.