David L. Robinson

Properties of the diffuse thalamocortical system and human personality: A direct test of Pavlovian/Eysenckian theory

Abstract Advances in the last few decades demonstrate the relevance of Pavlovs classification of behavioural types with respect to human individual differences and suggest that the hypothetical excitatory and inhibitory processes which he associated with these differences correspond to cortical and thalamic neuron populations of the diffuse thalamocortical system (DTS). Since the transmission properties or time constants of these DTS elements would correspond to the Pavlovian property of ‘strength’, and since they can be evaluated in human subjects (Robinson, 1981), it is possible to formulate hypotheses based on the fundamental principles of strength and balance which Pavlov employed to provide a causal explanation for temperamental types. A major finding is that covariation of the time constants equated with strength correlates 0.95 with covariation of extraversion and stability scores on the Eysenck Personality Questionnaire (EPQ). This result provides unequivocal support for the relationship between human individual differences and properties of the nervous system postulated by Pavlov and it also confirms the neurophysiological underpinning of Eysencks influential theory of human personality. In addition, the relationship between Pavlovian and Eysenckian concepts is clarified and EEG parameters are meaningfully related to personality differences.

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

Abstract Theory and research is described which led to the hypothesis that the choleric (E+N+) and melancholic (E−N+) temperaments are determined by differences in thalamocortical inhibition of brain-stem processes. An opportunity to test this hypothesis was provided by the recent discovery of 4, 7, and 10 Hz 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. Electroencephalography and Clinical Neurophysiology, 110, 1427–1434; (2000). The technical neurological, and psychological significance of ‘alpha’, ‘delta’, and ‘theta’ waves confounded in EEG evoked potentials: A study of peak amplitudes. Personality and Individual Differences, 28, 673–693]. These responses are attributed to the brain-stem, limbic, and thalamocortical arousal systems, respectively, and in the cited reports principal components analysis of data obtained from 93 participants confirmed the existence of predicted excitatory and inhibitory relationships. ANOVA was used in the present study to test the further prediction that there should be strong inhibition of the 4 Hz system by the 10 Hz system in melancholics (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 scores on the PCA inhibition factor obtained for the temperament groups, with temperament defined in terms of high and low EPQ extraversion (E) and neuroticism (N) scores. The significance of these results is discussed with reference to fundamental questions raised by Pavlovs pioneering research but left unanswered for the best part of a century. Implications for the future conduct of personality research are also considered.

Properties of the diffuse thalamocortical system, human intelligence and differentiated vs integrated modes of learning

Abstract In complementary reports Robinson (1982a, b) describes how the transmission characteristics or time constants of thalamic and cortical neuron populations of the diffuse thalamocortical system (DTS) can be evaluated in human subjects. Equating these constants with the Pavlovian property of ‘strength’ it was predicted that they should relate to Extraversion and Neuroticism scores on the Eysenck Personality Questionnaire (EPQ). This prediction was confirmed and the results provide direct support for the theories of Pavlov and Eysenck. The present report describes additional results which confirm predictions relating the DTS constants to performance on the Wechsler Adult Intelligence Scale (WAIS) and on the Embedded Figures Test (EFT). An important finding was that a measure of deviation from intermediate and ‘balanced’ values of the DTS constants loads to the extent of -0.80 on the WAIS ‘memory’ or ‘attention/ concentration’ factor. More generally, the results provide further support for Pavlovs conception of brain-behaviour relationships and suggest that the DTS plays a fundamental role in determining a broad spectrum of human psychological differences including some associated with the concepts of intelligence and cognitive style. These IQ and cognitive style differences are explained as the immediate and longer-term consequences, respectively, of differences in the distribution of background cortical activity mediated by the DTS.

The IQ factor: implications for intelligence theoryand measurement

Abstract The history of intelligence test development is considered with special reference to thedrift away from verbal tests and to the contemporary assumption that every factor produced bystatistical analysis of cognitive performance variables is an intelligence factor. To test thisassumption of universal test validity the Wechsler Adult Intelligence Scale (WAIS) and RavensAdvanced Progressive Matrices (RAPM) test were administered to 76 subjects, with equalnumbers of males and females and ages representing the whole adult life-span. Principalcomponents analyses (PCA) and multiple linear regression analyses (MLR) demonstrated thatage and sex account for 3% of the variance of IQ scores as compared to 1, 28 and 64% forCattells Gc, Gsar, and Gf factors, respectively. In addition, with IQ as a marker variable, andincluding age and sex, PCA was used to ascertain factor loadings for IQ on the three G factors.The highest loading of 0.77 was found for Gc whereas the loadings for Gsar and Gf were only0.31 and 0.19, respectively. These results support the conclusion that while there are multiplecognitive performance factors there is only one IQ factor and therefore only one validintelligence factor. Theoretical, social and research implications are discussed.

Age differences, cerebral arousability, and human intelligence

Abstract This report describes an empirical test of the cerebral arousability theory of intelligence which predicts that EEG-intelligence correlations will vary systematically as a function of age-related changes in cerebral arousal. Data were obtained from 76 subjects, in six different age-groups, with equal numbers of males and females in each group. AEP measures evaluated the amplitude, frequency and variability of EEG responses evoked by auditory stimulation. In accordance with arousability theory, but in contrast to an earlier report by D.E. Hendrickson (1982), the results show that there is no simple linear relationship between any of the EEG measures and general intelligence. There is a predicted increase in cerebral arousal during early adulthood with the highest arousal found for the 41–50 age-group and thereafter a steady decline with increasing age. Positive and negative Pearson product-moment correlations were found for variation of cerebral arousal with respect to WAIS ‘verbal’ and ‘spatial’ scores, respectively. These correlations conform exactly to the pattern predicted from arousability theory. Also, as expected from theory, the correlations for the youngest and oldest age-groups were generally greater in magnitude and more likely to be statistically significant with values ranging up to r = 0.78.

Exploring Structural Controls on Sumatran Earthquakes

A series of linked marine and land studies have recently targeted the Sumatra subduction zone, focusing on the 2004 and 2005 plate boundary earthquake ruptures in Indonesia. A collaborative research effort by scientists from the United Kingdom (UK Sumatra Consortium), Indonesia, United States, France, and Germany is focusing on imaging the crustal structure of the margin to examine controls on along-strike and updip earthquake rupture propagation. The fundamental science objective is to examine how margin architecture and properties control earthquake rupture location and propagation.