Participants completed a before/after and a similar/different relational task, which were presented on computer using the Implicit Relational Assessment Procedure (IRAP). They were subsequently exposed to the Kaufman Brief Intelligence Test (K-BIT). For each relational task, response latencies were measured on consistent trials, in which participants were required to respond in accordance with pre-established verbal relations, and on inconsistent trials, in which participants were required to respond against these relations. A difference-score was also calculated by subtracting consistent response latencies from those on inconsistent trials. The inconsistent trials and the difference-score were deemed to provide measures of relational flexibility. Results showed that faster responding on the IRAP, and smaller difference scores, predicted higher IQ. The findings suggest that relational flexibility is an important component of intelligence and might therefore be targeted in educational settings.