Thinking in opposites improves hypothesis testing performance in Wason’s rule discovery task

We investigated whether thinking in opposites can facilitate the solution process in Wason’s rule discovery task. Participants were exposed to three conditions: training prompting an analysis of the properties characterising the initial seed triple; training prompting the same action but subsequently demanding the identification of the opposites of each property and using it in the testing phase; and a no-prompt condition. Thinking in opposites turned out to be beneficial, almost doubling success rate. This improved efficacy was manifested in terms of higher flexibility in the testing phase, a more frequent identification of the critical property (ascending-descending) and, consequently, a more frequent discovery of the rule right at the first attempt. The other training condition had some effects on participants’ performance, but did not improve the solution discovery. Hence, it is specifically the prompt to think in opposites that seems beneficial. These results are discussed in relation to existing literature.