Eysenck's descriptive and biological theory of personality: A review of construct validity

Eysenck's descriptive and biological personality theory was reviewed from the perspective of construct validity. Factor analyses have consistently identified orthogonal personality dimensions of extraversion (E), neuroticism (N) and psychoticism. Defining characteristics of each dimension converge with those identified by factor analyses of Cattell's 16 PF, CPI and MMPI and average scores on the Eysenck Personality Questionnaire for 37 nations. These 3 dimensions reflecting variation of personality have been validated by differences in the degree of resemblance reflected by traits of dizygotic and monozygotic twins. Multivariate genetic analyses of responses to single items of the N and E scales have corroborated heritability of most items substantiated by conventional univariate analyses. Predictions applied to experimental substantiated by conventional univariate analyses. Predictions applied to experimental psychological findings more Frequently have validated the mediation of individual differences in the E dimension by some form of arousal than similar deductions from psychophysiology. That interindividual differences in arousability as opposed to basal arousal under neutral conditions can delineate extraverts from introverts was supported, in part, by evidence which I reviewed from literature on the electrodermal OR; P300 of event-related potentials (ERPs) and long latency somatosensory evoked potentials; stimulated salivation and startle eyeblink responses. A neuropsychological theory confirmed significance of predicted asymmetries in control repertoires of introverts (vs extraverts) which included (a) larger P2 amplitude of ERPs to speech stimuli at W3; (b) smaller right-to-left hemisphere ratio for amplitude of the P300 recorded from homologous parietal leads during a visual classification task; for male introverts (c) greater left hemisphere parietal cerebral blood flow and (d) larger amplitude of initial SCR on the right hand. These outcomes raised the possibility that the postulated asymmetric function of neural control systems might elucidate differential contributions of arousal differences within the brain to variations in the E dimension.