Selected Publications

An analysis of EEG responses in the alpha range of frequencies

International Journal of Neuroscience, 1983, 22, 81-98.

This paper explains the physical dynamics and oscillatory character of neural activity in terms of the basic physical properties and interaction of excitatory and inhibitory neurons. The results that are reported demonstrate the empirical validity of the theory and show how it can be applied to analyse human EEG responses in the alpha band of frequencies. The specific and immediate value of this paper is that it describes the only empirically tested theory that explains the oscillatory character of brain electrical activity. However, it also provides the theory and methods required to test the temperament and personality theories of Pavlov and Eysenck. Vague concepts such as “cerebral arousal” and “cerebral arousability” that have been used to suggest how differences in brain function might cause differences in temperament and personality are replaced by measurable parameters such as “natural frequency” and “damping ratio” that have an exact physical significance. For example, high arousability can be defined as the combination of high natural frequency and low damping ratio. When the natural frequency of a system is high it will tend to oscillate at this high frequency and these oscillations will continue for a longer period if the system has a low damping ratio. When the natural frequency is low and the damping ratio high the system will oscillate at a low frequency for a shorter period – or it may not oscillate at all if the degree of damping is too high. Apart from their physical significance, the natural frequency and damping parameters can be related to the basic “capacitance”, “inductance” and “resistance” properties of individual neurons and systems of neurons. For example, it can be shown that natural frequency is a direct index of the ratio of the relative influence or excitability of excitatory and inhibitory neurons.
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Properties of the diffuse thalamocortical system and human personality: A direct test of Pavlovian/Eysenckian theory

Personality and Individual Differences, 1982, 3, 1-16.

In this paper I test the temperament and personality theories of Pavlov and Eysenck using the new and more meaningful measures derived from my “excitation-inhibition” theory of brain electrical oscillations. Since introverts were found to have higher natural frequencies than extraverts there is confirmation of the prediction from Eysenck’s theory of higher cerebral arousability in the case of introverts. The more specific prediction from Pavlov’s theory was that “melancholic” individuals (E+ N-) should have higher cerebral arousability than “sanguine” (E+ N-) individuals. This prediction was also confirmed with results showing that the melancholic and sanguine temperament types are at the extremes of the natural frequency dimension. At this point in my research the role of damping was not well understood but since the melancholic and sanguine types are both characterised by low damping it was evident that the difference between these types can be attributed entirely to differences in natural frequency. The role of damping has been clarified in subsequent reports.
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Properties of the diffuse thalamocortical system, human intelligence and differentiated versus integrated modes of learning

Personality and Individual Differences, 1982, 3, 393-405.

From the beginning, I expected that differences in the functional character of the brain arousal systems would have a profound influence on cognitive performance. This is the first report in which I was able to demonstrate that the natural frequency and damping ratio parameters of the diffuse thalamocortical system relate to differences in cognitive performance as well as to differences in personality and temperament. The particular finding described in this article is that “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. The rationale for this study was based on Pavlovian concepts and findings rather than on any ideas of my own about the biological basis of intelligence. It was only later that I fully appreciated the functional significance of an intermediate degree of cerebral arousability and it was this that led ultimately to a more general understanding of the manner in which my arousability measures relate to intelligence differences.
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How personality relates to intelligence test performance: Implications for a theory of intelligence, ageing research and personality assessment

Personality and Individual Differences, 1985, 6, 203-216.

The results from my earlier EEG studies suggested that personality and temperament differences are intimately related to differences in cognitive performance despite the fact that personality and intelligence differences are normally regarded as separate fields of study. In this paper I report significant differences in the WAIS subtest profiles of introverts and extraverts. The results showed that introverts do better on the WAIS “verbal” subtests whereas extraverts do better on the “performance” subtests. In addition, it was possible to demonstrate that individuals in the middle of the E scale, who differed in terms of the Eysencks’ psychoticism dimension, also had different WAIS profiles. This was the first report in recent times to draw attention to relations that exist between personality and intelligence dimensions. It inspired subsequent research on this topic which preceded the contemporary interest in “emotional intelligence”. In my own research, this and other related studies were important milestones leading to an integrated conception of personality and intelligence that eventually contributed to the formulation of a single integrated biological theory of personality and intelligence.
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The Neurophysiological Bases of High IQ

International Journal of Neuroscience, 1989, 46, 209-234.

This paper tests the primary and fundamental principle on which my theory of intelligence is based. In my earlier research I had discovered that low and high cerebral arousability was associated with differences in WAIS subtest profiles and that there was a specific relationship between my arousability parameters and the WAIS ‘attention/concentration’ factor. In this paper I give a detailed account of my reasons for believing that an intermediate degree of cerebral arousability should be optimal for neurophysiological processes mediating the acquisition, retention and utilisation of information. The results confirmed my prediction that differences in general intelligence or “g” are caused by differences in cerebral arousability. The value of this paper is not just that it reports discovery of the biological basis of general intelligence but that it led me towards a more comprehensive theory of intelligence that provides a neurological explanation for all the major factors revealed by statistical analysis of test data.
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On the Neurological Bases of Intelligence and Intelligence Factors

In Rowe, H. A. H. (Ed.), Intelligence: Reconceptualization and Measurement. Lawrence Erlbaum: New Jersey, 1991.

In this book chapter I provide the first account of a more comprehensive theory of intelligence that can account for all of the major factors of intelligence.
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The EEG and intelligence: An appraisal of methods and theories

Personality and Individual Differences, 1993, 15,  695-716.

Original empirical findings are presented in 7 figures to refute the “cognitive processing” interpretation of “event-related” changes in EEG potentials caused by experimental manipulation of cognitive tasks. Conceptual and methodological problems of correlational studies of the relationship between EEG response variables and intelligence test scores are also addressed and there is criticism of the vague and general concepts of “neural transmission speed” and “neural efficiency” that have been used to account for the results of such studies. It is argued that these “theories” are free-floating ideas that are entirely unrelated to what is known about the nature and origin of EEG activity; and that they are equally unrelated to the statistical and psychological facts concerning intelligence test scores that have been recorded in the general literature. It is noted that the cerebral arousability theory of intelligence explains the findings obtained in both experimental and correlational EEG studies. Unlike the other theories mentioned, it does so in terms of known functional properties of neural systems that can account for the oscillatory character of EEG activity and explain systematic differences in EEG activity. As a consequence, it is possible to use EEG measures to evaluate neurological differences and to predict corresponding differences in cognitive performance. It is concluded that significant advances in the study of relationships between EEG variables and cognitive performance can only be expected when consideration is given to the physical and neurological significance of EEG activity. This is just as important for the development and application of meaningful methods of measurement and analysis as it is for the development of a useful theory.
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A test of the Hendrickson postulate that reduced EEG response variance causes increased AEP contour length: Implications for the "neural transmission errors" theory of intelligence

Personality and Individual Differences, 1997, 22, 173-182.

This paper deals with the neurophysiological causes of intelligence variation. The Hendrickson theory was formulated to explain the observation, reported in several studies, that there were more peaks in the averaged evoked EEG responses of high IQ individuals. The Hendrickson theory attributed the greater number of peaks in the averaged evoked potential waveform to less variability in the individual EEG responses from which the averaged evoked potential was derived. It was suggested that greater variability of the individual EEG responses would cause some peaks to be averaged out so that fewer peaks would appear in the final averaged waveform. It was argued, that less variability of the individual responses indicated fewer neural transmission errors and that this could explain higher intelligence. There are many points where the Hendrickson theory deviates from our present knowledge of the nature of EEG activity, and of the functional characteristics of neurons and systems of neurons, but it has appealed to quite a number of psychologists in the field, and has been cited frequently. In my paper, I draw attention to the neurophysiological errors and to methodological problems in the Hendricksons’ empirical work. Most importantly, the empirical findings that I report refute the Hendricksons’ claim that there are more peaks in the averaged evoked potential waveform when there is less variability of the individual evoked potentials from which the averaged evoked potential is computed. This paper is useful because it demonstrates that the Hendrickson theory is based on a false premise.
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Intelligence differences: Neural transmission errors or cerebral arousability?

Kybernetes, 1997, 26, 407-424.

This paper examines the relative merits of two contemporary theories that offer explanations for differences in human intelligence by reference to neurological differences. The theories are compared in terms of: a) their ability to explain the results of specific studies that have reported statistically significant correlations between individual differences in EEG responses and intelligence test scores; b) their ability to provide a valid account of the neurological source and physical character of EEG responses to sensory stimulation; c) their ability to account for what is currently known about the statistical and psychological character of individual differences measured by intelligence tests. It is concluded that the Hendrickson theory fails in terms of all three criteria. In contrast, the cerebral arousability theory of intelligence is consistent with what is currently known about the functional character of neurons and neural systems. It extends our knowledge of the physical character of the activity of neural systems and how this causes EEG oscillations, and it provides an explanation for EEG correlates of intelligence differences that can account for much that is known about the statistical and psychological character of such differences. The value of the paper is that it clarifies fundamental concepts concerning the manner in which differences in brain function can influence cognitive performance and it has an important bearing on the nature of EEG methods that can be used to test the validity of these concepts.
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Age differences, cerebral arousability, and human intelligence

Personality and Individual Differences, 1997, 23, 601-608.

In an earlier study (Robinson, 1989) I was able to confirm the expectation from theory that high IQ scores are associated with an intermediate degree of cerebral arousability. Since it is known that the excitability or arousability of cerebral processes varies as a function of age it is possible to test whether age-related changes in excitability will produce systematic variation of EEG-intelligence correlations in a way that conforms to theoretical expectations. Another important objective was to resolve confusion in the literature that has been caused by inconsistencies in the magnitude and sign of EEG-intelligence correlations. The results conform to theoretical expectations and explain why simple linear relationships between EEG and intelligence measures are usually only observed in studies of younger or older age groups. There is also new information about the psychological consequences of age-related neurophysiological changes.
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Sex differences in brain activity, personality, and intelligence: A test of arousability theory

Personality and Individual Differences, 1998, 25, 1133-1152.

This article begins by summarizing the literature on sex differences in personality, temperament and cognitive performance. This literature indicates that female groups normally obtain higher neuroticism and lower psychoticism scores than males, and that, despite similar scores for males and females on measures of general intelligence, females perform less well than males on tests that require the ability to concentrate attention and avoid distraction. Since there is evidence from my earlier EEG studies that these particular personality and cognitive differences relate to differences in cerebral arousability there was reason to suppose that males and females might differ in terms of cerebral arousability, and if so, that this would account for the reported differences in personality and cognitive performance. The results described in this paper confirm the reports of sex differences in personality and cognition in the general literature. In addition, a principal components analysis reveals that these personality and cognitive differences are related to each other and also to differences in both behavioural and cerebral arousal. This result extends the domain of arousability theory and provides new information about the origin and character of the psychological characteristics that distinguish males and females.
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The technical, neurological, and psychological significance of 'alpha', 'delta', and 'theta' waves confounded in EEG evoked potentials: A study of peak latencies

Electroencephalography and Clinical Neurophysiology, 1999, 110, 1427-1434.

One of the fundamental principles on which my theory of personality and temperament is based is that there are differences in the relative influence of cerebral and brain-stem processes that have a profound and pervasive influence on the way in which people think, feel and act. As is well known, the brain-stem ascending reticular activating system has a general excitatory influence on the cerebrum, whereas the overall influence of the cerebrum on brain-stem processes is inhibitory. It is my thesis that the relative influence of ascending excitation and descending inhibition varies from person to person and that this variation causes the most pronounced and easily observed differences in temperament and personality, and that an extreme imbalance will result in psychiatric illness. This concept is supported by my earlier research which evaluated differences in cerebral excitability but I was unable to obtain separate measures of the excitability of brain-stem and cerebral processes. However, my study of the neurophysiological literature has indicated that 10 Hz and 4 Hz EEG components are generated by thalamocortical and brain-stem processes, respectively. Thus, by examining how these different frequency components vary from person to person it is possible to test the prediction that there should be a negative correlation indicating that the 10 Hz component inhibits the 4 Hz component. In this paper, the first of three complementary reports, I describe the results obtained from a very comprehensive study of the latencies of peaks in the 10 Hz and 4 Hz waveforms and demonstrate the existence of the predicted inhibitory relationship. The methodological innovation described in this paper was subsequently employed by other investigators and in their very recent article Schutter et al. [Clinical Neurophysiology, 117, (2006), 381–387] conclude that “Robinson’s contribution in Clinical Neurophysiology (1999;110:1427–1434) on the technical, physiological, and psychological significance of frequency bandwidths in EEG evoked potentials hallmarked the onset of a new field of research, wherein different EEG rhythms in the cortical EEG reflect the different subcortico-thalamic-cortical projections.”
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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, 2000, 28, 673-693.

This is the second of the three complementary papers mentioned above. In this report I present an equally comprehensive study of the amplitudes of the 10 Hz and 4 Hz peaks. The results again demonstrate the predicted negative relationship indicating inhibition of the 4 Hz amplitudes by the 10 Hz amplitudes.
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How brain arousal systems determine different temperament types and the major dimensions of personality

Personality and individual Differences, 2001, 31, 1233-1259.

Having established the existence of the predicted negative relationship between the 10 Hz and 4 Hz components of the EEG response to sensory stimulation this study uses a measure of the strength of the inhibitory effect to test the further prediction that inhibition of the 4 Hz waveform by the 10 Hz waveform will be greatest in individuals with a melancholic temperament (introversion and high emotionality), least in individuals with the choleric temperament (extraversion and high emotionality), and that there should be an intermediate degree of inhibition in the case of sanguine individuals (extraversion and low emotionality) and phlegmatics (introversion and low emotionality). This prediction was confirmed in a clear and unequivocal manner. I believe that this result represents a very significant advance in our understanding of the biological bases of personality and temperament differences. There are also important implications concerning the methods used to assess EEG differences and personality differences and there is the prospect of using EEG methods to diagnose the psychiatric illness that would be expected to occur when there is an extreme imbalance of cerebral and brain-stem processes, and to monitor the effects of drug therapy.
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In pursuit of knowledge

International Journal of Psychophysiology, 2006, 62, 394-410.

This article appeared in a special issue of  IJP - inspired by the author’s perception that many researchers do not have an adequate understanding of the role of theory in science and that this impairs scientific progress. Professor Susan Greenfield expressed a similar view in her Preface where she states that: “this collection of papers will not come up with easy answers, but it provides a very timely counterpoint to the information-rich, knowledge-poor, scientific appetite that characterises current brain research.” I was Guest Editor of the special issue, along with my colleague Dr. Jiri Wackermann, and we encouraged contributors to write about the role of theory in the conduct of their own research and to feel free to express their views concerning the nature of theory and the role of theory in science. My own contribution argues that all knowledge is theory and that the principal objective in science is to increase knowledge by developing better theories. In order to examine this claim my article begins with the proposition that to understand the nature of knowledge, and how best to acquire it, one must look first at how the brain abstracts knowledge from the information provided by sensory receptors. It is acknowledged that there is still much about brain function that is not understood but it is argued that knowledge of learning and of neural systems has advanced to the point where it is possible to identify the main features of the natural process of knowledge acquisition. The theory of knowledge that is developed in the article casts new light on the nature of knowledge, it explains “personality” bias in the process of knowledge acquisition, it provides a more precise understanding of the intellectual process of theory generation, of the role of theory in science, and of the principles and methods that enable science to increase knowledge.
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Brain function, mental experience and personality

The Netherlands Journal of Psychology, 2009, 64, 152-167.

This was an invited contribution to a special issue of NJP on the biological basis of the emotions. The invitation prompted me to develop and clarify those aspects of my theory that link differences in emotionality to differences in personality. One objective of the article was to develop a taxonomy of ‘sensations’, ‘feelings’ and ‘basic emotions’, and to distinguish these from personality traits. A second objective was to clarify the relationship between emotional experience and personality. A third objective was to describe how neurological differences can cause differences in the dynamics of emotional experience, either directly or as a consequence of a bias in learning, that are manifest as differences in personality or temperament and, in extreme cases, as neurotic disorders. It is suggested that bias in emotional experience initiated by individual differences in the natural frequencies and damping ratios of thalamocortical oscillators is perpetuated and augmented by biased learning.
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