With reference to Wason’s 2-4-6 rule discovery task, this study investigated the effects of a simple training session that prompted participants to “think in opposites”. The results showed a significant improvement in performance under the training condition when compared to the control condition, both in terms of the proportion of participants who discovered the correct rule and how quickly it was discovered. An analysis of whether or not participant submitted test triples formed of descending numbers showed that fewer participants under the control condition considered ascending/descending to represent a critical dimension and, in any case, this occurred later (that is, after more test triples) than in the training condition. These results are discussed in relation to previous literature showing improvements in performance that were prompted by strategies involving “contrast” as a critical factor. The limitations of the study are discussed, as well as the benefits of a training program like this, which is non-content related.