How brain arousal systems determine different temperament types and the major dimensions of personality

Theory and research is described which led to the hypothesis that the chole ric (E+N+) and melancholic (E-N+) temperaments are determined by difference s in thalamocortical inhibition of brain-stem processes. An opportunity to test this hypothesis was provided by the recent discovery of 4, 7, and 10 H z response waves confounded in EEG averaged evoked potentials [Robinson, D. L. (1999b). The technical, neurological, and psychological significance of 'alpha' 'theta' and 'delta' waves confounded in EEG evoked potentials: 1. A study of peak latencies. Eleetroencephalography and Clinical Neurophysiol ogy, 110, 1427-1434; (2000). The technical neurological, and psychological significance of 'alpha', 'delta', and 'theta' waves confounded in EEG evoke d potentials: A study of peak amplitudes. Personality and Individual Differ ences, 28, 673-6931. These responses are attributed to the brain-stem, limb ic, and thalamocortical arousal systems, respectively, and in the cited rep orts principal components analysis of data obtained from 93 participants co nfirmed the existence of predicted excitatory and inhibitory relationships. ANOVA was used in the present study to test the further prediction that th ere should be strong inhibition of the 4 Hz system by the 10 Hz system in m elancholics (E-N+) and weak inhibition of the 4 Hz system in cholerics (E+N +), with median inhibition predicted for the other temperament types. There was a large and statistically significant difference between the mean scor es on the PCA inhibition factor obtained for the temperament groups, with t emperament defined in terms of high and low EPQ extraversion (E) and neurot icism (N) scores. The significance of these results is discussed with refer ence to fundamental questions raised by Pavlov's pioneering research but le ft unanswered for the best part of a century. Implications for the future c onduct of personality research are also considered. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.