Extraversion and cortical activation: effects of task complexity

In the present study we analysed the role of task complexity as a possible moderating variable on the relationship between extraversion (E) and the level of cortical activation. In 58 participants we measured the extent of “Event-Related Desynchronization” (ERD) in the human EEG during performance of a modified version of Stankov’s Triplet Numbers test—a test consisting of five increasingly complex conditions that differ with respect to the number of mental operations needed to perform successfully on the task. Our results suggest a moderating influence of task complexity on the relationship between E and cortical activation: It seems that in the easier test conditions the introverts were more likely to display a lower cortical activation (as compared to extraverts), whereas in more complex test conditions the data tend to support Eysenck’s (1967) hypothesis of more activation in introverts as compared to extraverts. Most interestingly, these E-effects were—as in a former study—exclusively restricted to the lower alpha frequency range (6–8 Hz). The findings are discussed with respect to the functional meaning of lower alpha activity.