Fluid intelligence and neural efficiency: effects of task complexity and sex

On the basis of the neural efficiency concept of human intelligence-which suggests a more efficient use of the cortex (or even the brain) in brighter individuals-we analyzed the role of sex and task complexity as possible moderating variables in the relationship between cortical activation and psychometric intelligence. In 28 males and 30 females we measured cortical activation in the EEG during performance of a modified variant of Stankov's Triplet Numbers test-a test consisting of five increasingly complex conditions. Preliminary analyses showed that both sex- and intelligence-related effects on cortical activation became more evident when we focused on participants' fluid intelligence scores instead of just using scores of general mental ability. As expected, we observed an increase of cortical activation with increasing task complexity, but no moderating influence of task complexity on the intelligence-activation relationship was found. Moreover, our data suggest that the males were more likely to produce cortical activation patterns in line with the neural efficiency hypothesis (i.e. less activation in brighter individuals), whereas in females no significant differences were found. (C) 2002 Elsevier Ltd. All rights reserved.