States vs. Traits

Abstract

Hans-Jürgen Eysenck suggested that introverts are characterized by greater cortical arousal or arousability than extraverts. This prediction was tested in several studies that used the electroencephalogram (EEG) to index cortical activity, but the relations between the EEG measures and Extraversion are typically small. Possibly, situational factors that are external to the laboratory may act as nuisance variables and affect cortical activity, thus, mitigating the relation between arousal or arousability and Extraversion. To test this hypothesis, resting EEG was acquired on four occasions of measurement and Extraversion was assessed by questionnaire. A structural equation model (SEM) represented cortical arousal, arousability, and external factors. This analysis suggested that (1) arousal and arousability are independent factors, (2) external factors only marginally contribute to the variance of the EEG measures, and (3) the relations between the EEG measures and Extraversion were insignificant even if external factors were statistically controlled.