Eysenck's model of personality is distinctive in a number of respects. First, Eysenck proposes that 'the study of personality has two interlocking aspects'. The first aspect is descriptive or taxonomic and it focuses on establishing the units to be used in summarizing the ways in which individuals differ. The second is concerned with the causal elements, and it is here that Eysenck makes one of his distinctive contributions. He recognizes the critical role played by learning and environmental forces, but he maintains that we also must account to the fact that the effect of a given situation varies for different individuals. In addition, we must recognize the determining, causal role played by biological factors.
Eysenck's theory specifies a causal chain in which a biological substrate is responsible for individual differences on fundamental dimensions of personality. Eysenck's model of personality includes three basic typological dimensions which emerge consistently from factor-analytic studies of personality questionnaires. Eysenck regards all three dimensions as essentially normally distributed within the population. Eysenck advances three arguments that biological factors play a critical role in determining individual differences on the three types. First, the same factors have consistently emerged in investigations of personality structure in widely divergent cultures; second, individuals tend to retain their position o these dimensions across time; third, there is evidence of a substantial heritable component in individual differences on the three dimensions. Eysenck stipulates that an adequate theory of personality must generate testable hypothesis. In this respect, Eysenck' model has achieved exemplary success.
Eysenck received his PhD in 1940, but his status as an enemy alien jeopardized his employment prospects. Through a fortuitous chain of events, he became research psychologist at the Mill Hill emergency Hospital, a World War II psychiatric facility. Eysenck began research here, advocating dimensional analysis. He also identified the two major dimensions in neurotic patients, extraversion-introversion and neuroticism and stability, which he subsequently applied to 'normal people'as well. After the war Eysenck became director of the psychology Dept in the new institute of psychiatry established at Maudsley Hospital, as well as professor of psychology at the University of London. This is where Eysenck's research on behaviour therapy began in earnest Under Eysenck's direction the department has been a center for clinical training and for research in personality measurement and behaviour genetics. in 1994, Eysenck received the American Psychological Society's William James Fellow Award.
Later Galen, Kant and Wundt elaborated and expanded on this model presented by Hippocrates. The excess of any humor was considered to be responsible of an individual's distinctive emotional qualities: the Sanguine, the Melancholic, the Choleric and the Phlegmatic. Individuals are defined in terms of their position in a two-dimensional space in which the four temperaments represent extreme positions in the four quadrants. This system predicts Eysenck original two dimensional models: Neurotic vs Stable, Extraversion vs Introversion. The final contribution of Eysenck's descriptive taxonomy comes from Carl Jung.
To test Jung's model, Eysenck (1947) examined the clinical files for 700 neurotic patients at the Mill Hill Emergency Hospital. He subjected 39 relevant items dealing with the client's history and behaviour to factor analysis which revealed two bipolar factors. He interpreted on e factor as general neuroticism and the second factor distinguished between patients whose neurotic symptoms were associated either with anxiety or with hysterical symptoms were associated either with anxiety or with hysterical symptoms. Eysenck introduced the term Dysthemia to refer to the anxiety disorders Jung had called Psycasthenia, and he retained the hysteria designation for the other class of disorders. Eysenck generalized these results to argue that the dimension of extraversion and neuroticism provide a basic structure for describing individual differences in temperament.
Eysenck's dimensional approach, combined with his hierarchical model of constituent traits underlying a more general type of psychoticism, justifies his claim that psychoticism provides a useful dimension in describing unsocialized, unusual and poorly controlled behaviour in non-clinical individuals.
If excitatory neural processes can be understood to facilitate the acquisition of conditioned responses, then a basic prediction from Eysenck's 1957 model is that all other things being equal, introverts have a nervous system that permits them to condition more readily than extraverts.
Eysenck's second causal model differs from the first in three important respects. First, he relates difference between introverts and extraverts to difference in arousal levels rather than excitation-inhibition and he localizes the central nervous system structures within which that differences occurs. Second, he provides a neurological explanation for observed differences in neuroticism-stability. Third, he describes a curvilinear relationship between intensity of external stimulation and degree of cortical arousal with differing curves for introverts and extraverts.
In his 1967 statement of the theory, Eysenck relates differences in introversion-extraversion to levels of activity inn the ascending reticular activation system (ARAS). In very general terms activity in the ARAS serves to stimulate the cerebral cortex, leading to higher corical arousal. Because of greater ARAS activity, introverts are characterized by higher levels of cortical arousal than extraverts and this neurological difference serves as a causal basis for observed differences on the introversion-extraversion typology. That is, introverts have lower thresholds of ARAS arousal than extraverts. In addition, individual differences in emotionality or neuroticism depend on levels of activity in the viscoral brain (VB) which consists of the hippocampus, amygdale, cingulum, septum and hypothalamus.
These structures, which are often referred to as the limbic system, have been related to emotional states through the operation of the autonomic nervous system. Neurotic individuals are characterized by greater activation levels and lower thresholds within the VB. The independence of these two causal systems and of the resulting extraversion and neuroticism dimensions are complicated by a one-way link between the ARAS and VB. If a person is cortically aroused, there need not be any emotional (VB) activation. Emotional activation, however, guarantees that cortical arousal will occur.
The third new aspect of Eysenck's 1967 model specifies a curvilinear relationship between stimulation and cortical arousal, with introverts reaching their maximum arousal at a lower level of stimulation then extraverts. In Eysenck's newer model, introverts are postulated to be more aroused and more arousable than extraverts. Eysenck again draws on the work of Pavlov, this time adopting Pavlov's concept of 'strength of the nervous system'. A strong nervous system can tolerate intense stimulation, and it is less sensitive to stimulation than a weak nervous system.
Personal History
Hans Jurgen Eysenck was born in Berlin, Germany on March 4. 1916. He was raised as a protestant, but his sympathies were with the persecuted Jews and hated their persecutors. In 1934, when he was 18, Eysenck refused to join the German Military, and he migrated to London. He wanted to study sub-atomic physics at the University of London, but he turned to psychology when he was told that he lacked the prerequisites for physics. Eysenck's early interest in natural and physical science has continued to characterize his approach to psychology. Eysenck studied with the eminent psychologist, Sir Cyril Burt.Eysenck received his PhD in 1940, but his status as an enemy alien jeopardized his employment prospects. Through a fortuitous chain of events, he became research psychologist at the Mill Hill emergency Hospital, a World War II psychiatric facility. Eysenck began research here, advocating dimensional analysis. He also identified the two major dimensions in neurotic patients, extraversion-introversion and neuroticism and stability, which he subsequently applied to 'normal people'as well. After the war Eysenck became director of the psychology Dept in the new institute of psychiatry established at Maudsley Hospital, as well as professor of psychology at the University of London. This is where Eysenck's research on behaviour therapy began in earnest Under Eysenck's direction the department has been a center for clinical training and for research in personality measurement and behaviour genetics. in 1994, Eysenck received the American Psychological Society's William James Fellow Award.
The Description of Temperament
Extraversion and Neuroticism
Eysenck places his model in historical perspective by describing how two of the major personality types, extraversion and neuroticism can be traced back through history to temperament systems described in terms of four humors by Greek writers Hippocrates and Galen. These four humors were blood, phlegm, black bile, and yellow bile. The way in which these humors were combined determined an individual's health and character. Eysenck argues that these ideas embody the three main notions which characterize modern work in personality. First, behaviour is best described in terms of traits that characterize people in varying degrees. Second, these traits combine to define more fundamental types. Third, individual differences on these types are based on constitutional (genetic, neurological and bio-chemical) factors To a large extent, these three notions serve as Eysenck's credo.Later Galen, Kant and Wundt elaborated and expanded on this model presented by Hippocrates. The excess of any humor was considered to be responsible of an individual's distinctive emotional qualities: the Sanguine, the Melancholic, the Choleric and the Phlegmatic. Individuals are defined in terms of their position in a two-dimensional space in which the four temperaments represent extreme positions in the four quadrants. This system predicts Eysenck original two dimensional models: Neurotic vs Stable, Extraversion vs Introversion. The final contribution of Eysenck's descriptive taxonomy comes from Carl Jung.
To test Jung's model, Eysenck (1947) examined the clinical files for 700 neurotic patients at the Mill Hill Emergency Hospital. He subjected 39 relevant items dealing with the client's history and behaviour to factor analysis which revealed two bipolar factors. He interpreted on e factor as general neuroticism and the second factor distinguished between patients whose neurotic symptoms were associated either with anxiety or with hysterical symptoms were associated either with anxiety or with hysterical symptoms. Eysenck introduced the term Dysthemia to refer to the anxiety disorders Jung had called Psycasthenia, and he retained the hysteria designation for the other class of disorders. Eysenck generalized these results to argue that the dimension of extraversion and neuroticism provide a basic structure for describing individual differences in temperament.
Eysenck provides the following description:
- A typical extravert is sociable, likes parties, has many friends, needs to have people to talk to, and does not like reading or studying by himself and is generally an impulsive individual.
- The typical Neurotic is anxious, worrying individual, moody and frequently depressed.
- Eysenck emphasizes that these descriptions refer to the plenotypic or expressed aspect of personality. Observed behaviour is a function of the interaction between constitutional characteristics and the experienced environment. In this important aspect, Eysenck provides a bio-social model of personality.
Psychoticism
In more recent years Eysenck has expanded his original two-dimensional descriptive model by adding a third descriptive dimension of psychoticism. The psychotic dimension subsumes the continuum from normal behaviour to schizophrenic and other psychotic states in which contact is lost with reality and there is severely disordered cognitions, affect and behaviour. This orientation is consistent with Eysenck's general dimensional approach to conceptualizing and measuring psychopathology.Eysenck's dimensional approach, combined with his hierarchical model of constituent traits underlying a more general type of psychoticism, justifies his claim that psychoticism provides a useful dimension in describing unsocialized, unusual and poorly controlled behaviour in non-clinical individuals.
Causual Models
Eysenck's three dimensional taxonomy provides a system for describing different types of individuals in terms of their characteristic behaviour patterns. Psychoticism, Introversion and Neuroticism refer to the observed or phenotypic components of personality. Eysenck's attempt to specify the underlying or genotypic factors responsible for observed variations in behaviour hinges on identification of physiological differences that vary with high or low status on the typological dimensions. Eysenck has proposed two explanatory models. The first model (Eysenck 1957) accounted for differences between introverts and extraverts in terms of central nervous system differences in levels of inhibitory and excitatory neural processes. The second model (Eysenck, 1967) accounted for differences between Introverts and Extroverts in terms of levels of critical arousal and Neurotic stables in terms of levels of visceral brain activation.Eysenck (1957)
Eysenck proposed that introverts are characterized by more excitatory neural processes and extraverts by more inhibitory neural processes. Eysenck summarized his position in his typological postulate:- Individuals in whom excitatory potential is generated slowly and in whom exitatory potential so generated are relatively weak, are thereby predisposed to develop extraverted patterns of behaviour and to develop hysterical-psychopathic disorders in cases of neurotic breakdown.
- Individuals in whom excitatory potential is generated quickly and in whom excitatory potentials so generated to develop introverted patterns of behaviour and to develop dysthymic disorders in case of neurotic breakdown.
- Individuals in whom reactive inhibition is developed quickly in whom strong reactive inhibitions are generated and in whom reactive inhibition is dissipated slowly, are thereby predisposed to develop extraverted patterns of behaviour and to develop hysterical-psychopatic disorders in case of neurotic breakdown.
- Individuals in whom reactive inhibition is developed slowly, in whom weak reactive inhibitions are generated and in whom reactive inhibition is dissipated quickly, are thereby predisposed to develop introverted patterns of behaviour and to develop dysthemic disorders in case of neurotic breakdown.
If excitatory neural processes can be understood to facilitate the acquisition of conditioned responses, then a basic prediction from Eysenck's 1957 model is that all other things being equal, introverts have a nervous system that permits them to condition more readily than extraverts.
Eysenck (1967)
Eysenck's second causal model differs from the first in three important respects. First, he relates difference between introverts and extraverts to difference in arousal levels rather than excitation-inhibition and he localizes the central nervous system structures within which that differences occurs. Second, he provides a neurological explanation for observed differences in neuroticism-stability. Third, he describes a curvilinear relationship between intensity of external stimulation and degree of cortical arousal with differing curves for introverts and extraverts.
In his 1967 statement of the theory, Eysenck relates differences in introversion-extraversion to levels of activity inn the ascending reticular activation system (ARAS). In very general terms activity in the ARAS serves to stimulate the cerebral cortex, leading to higher corical arousal. Because of greater ARAS activity, introverts are characterized by higher levels of cortical arousal than extraverts and this neurological difference serves as a causal basis for observed differences on the introversion-extraversion typology. That is, introverts have lower thresholds of ARAS arousal than extraverts. In addition, individual differences in emotionality or neuroticism depend on levels of activity in the viscoral brain (VB) which consists of the hippocampus, amygdale, cingulum, septum and hypothalamus.
These structures, which are often referred to as the limbic system, have been related to emotional states through the operation of the autonomic nervous system. Neurotic individuals are characterized by greater activation levels and lower thresholds within the VB. The independence of these two causal systems and of the resulting extraversion and neuroticism dimensions are complicated by a one-way link between the ARAS and VB. If a person is cortically aroused, there need not be any emotional (VB) activation. Emotional activation, however, guarantees that cortical arousal will occur.
The third new aspect of Eysenck's 1967 model specifies a curvilinear relationship between stimulation and cortical arousal, with introverts reaching their maximum arousal at a lower level of stimulation then extraverts. In Eysenck's newer model, introverts are postulated to be more aroused and more arousable than extraverts. Eysenck again draws on the work of Pavlov, this time adopting Pavlov's concept of 'strength of the nervous system'. A strong nervous system can tolerate intense stimulation, and it is less sensitive to stimulation than a weak nervous system.
Summary
- Eysenck proposed that the study of personality has two interlocking aspects. The aspect is 'descriptive' and the second is 'causal' Eysenck's approach to personality is virtuality unique in that he specifies a causal chain in which a biological sub-strata is responsible for individual differences on fundamental dimension of personality.
- Eysenck draws on the work of Greek writers Hippocrates, Galen and Carl Jung to describe the temperamental components of personality structure. The Greek writers have described four major temperamental types, Sanguine, Melancholicl, Choleric, Phlegmatic. Through his research, Eysenck found basic dimensions to personality-introversion, extraversion and neuroticism. Later he added other component/dimension psychoticism. Eysenck tries to relate these dimensions with the four temperamental types.
- Eysenck came up with two models, 1957 & 1967, to explain the causes for the differences of behaviour of introverts and extraverts. In the first model he is of the view that the fundamental causal distiction between introverts and extraverts is that introverts have a low ratio of inhibitory to excitatory processes and extraverts have a high ratio of inhibitory to excitatory neural processes.
- In the second causal model of 1967, he relates differences between introverts and extraverts to differences in arousal levels and localizes the central nervous system structures within which that differences occur, he provides a neurological explanation for the observed differences in neuroticism-stability; he describes a curvilinear relationship between intensity of external stimulation and degree of cortical arousal, with differing curves for introverts and extraverts.
