The moderating influence of extraversion on the relationship between IQ and cortical activation

There is converging empirical evidence for a more efficient use of the brain in high IQ individuals (i.e. the neural efficiency hypothesis). In this study the personality dimension extraversion (E), which has also been linked to individual differences in central nervous system activity, has been additionally taken into consideration. We measured the so-called Event-Related Desynchronization (ERD) in the EEG during performance of a well-known elementary cognitive task, the so-called Posner task. In addition, cortical activation at rest was analyzed. As IQ-ERD results are covered elsewhere [cf. Neubauer, A. C. Fink, A. & Schrausser, D. G. Intelligence and neural efficiency: The influence of task content and sex on brain-IQ relationship. (submitted for publication), the aim of this paper is to specifically analyze IQ and E group differences in cortical activation patterns. We observed significant IQ by E interactions during rest and cognitive activity in the lower alpha band: The pattern of this interaction suggests that during cognitive activity the extraverts were more likely to produce activation patterns in line with the neural efficiency hypothesis (i.e. less activation in more intelligent participants), whereas at rest the introverted group displayed this inverse relationship between IQ and cortical activation. Alternatively interpreted, at rest the hypothesized lower cortical arousal in extraverts as compared to introverts was only found in low IQ individuals, whereas during task performance only brighter individuals matched this hypothesis. (C) 2002 Elsevier Science Ltd. All rights reserved.