Schizothymia-cyclothymia as a dimension of personality. II. Experimental

Investigating racing thoughts via ocular temporal windows: deficits in the control of automatic perceptual processes

BACKGROUND

Racing thoughts have been found in several states of bipolar disorder (BD), but also in healthy populations with subclinical mood alterations. The evaluation of racing thoughts relies on subjective reports, and objective measures are sparse. The current study aims at finding an objective neuropsychological equivalent of racing thoughts in a mixed group of BD patients and healthy controls by using a bistable perception paradigm.

METHOD

Eighty-three included participants formed three groups based on participants' levels of racing thoughts reported via the Racing and Crowded Thoughts Questionnaire. Participants reported reversals in their perception during viewing of the bistable Necker cube either spontaneously, while asked to focus on one interpretation of the cube, or while asked to accelerate perceptual reversals. The dynamics of perceptual alternations were studied both at a conscious level (with manual temporal windows reflecting perceptual reversals) and at a more automatic level (with ocular temporal windows derived from ocular fixations).

RESULTS

The rate of windows was less modulated by attentional conditions in participants with racing thoughts, and most clearly so for ocular windows. The rate of ocular windows was especially high when participants with racing thoughts were asked to focus on one interpretation of the Necker cube and when they received these instructions for the first time.

CONCLUSIONS

Our results indicate that in subjects with racing thoughts automatic perceptual processes escape cognitive control mechanisms. Racing thoughts may involve not only conscious thought mechanisms but also more automatic processes.

How valid is the psychoticism scale? A comment on the Van Kampen critique

Van Kampen (1993) has published a paper in which he criticizes the concept of psychoticism and the use of the P scale as a measuring device, and advances measures for his own S scale and its validity. This reply attempts to clarify the notion of ‘validity’, and to demonstrate that there is a considerable body of experimental evidence to show that P has a high degree of construct validity, whereas the Van Kampen S scale lacks completely any degree of construct validity. Several examples are given of how the experimental evidence legitimates both the P scale, and the theory (nomological network) on which it is based.

The 3DPT dimensions S, E, and N: A critical evaluation of Eysenck's Psychoticism model

In this article a critical evaluation is given of Eysenck's Psychoticism model. It is argued that in this model two sub‐models can be distinguished, which, contrary to Eysenck's presentation, cannot be regarded as true extensions of each other. With respect to one of these models, the ‚genotypic’︁ P‐model, the theory is criticized in that both schizophrenia and affective psychosis are determined by a common genetic predisposition which can phenotypically manifest itself in variations of P. Instead of this theory, the likelihood is put forward that a high EPQ‐P score, albeit in combination with a high N and a low E score (and notwithstanding the fact that criminals or psychopaths can also obtain high P scores), is (only) related to the schizoid state, and hence, that P seems to be relevant either as a predisposing factor contributing to the development of schizophrenic psychosis, or as a factor on which biological relatives of schizophrenics obtain higher scores on average than normals do. In this respect, Eysenck's theory that the non‐schizoid form of psychopathy can also be found among first‐degree relatives of schizophrenics, and hence, that psychopathy and schizoidia are genetically related, is also criticized. Furthermore, it is argued that Eysenck's EPQ‐P scale is not optimal for measuring those traits of the schizoid personality which are independent of N and/or E. Both arguments regarding the contents of this scale and arguments with respect to the demonstrated lack of invariance of the EPQ‐P factor are adduced to support this statement. Thus, an alternative scale for measuring ‚P’︁ (labelled S or Insensitivity) was designed by us. The S‐scale is based on literature concerning the schizoid state and reflects the results of a series of principal components analyses of (potential) S items, together with N and E items, put into execution with the intention of investigating the invariance of the S factor (and of E and N) with respect to six sample and other parameters. These investigations were carried out on a large, representative sample of the Dutch population. Additional investigations were carried out concerning the reliability and validity of the three newly formed scales. The results of these investigations turned out to be very satisfactory or, in some respects, at least promising. Finally, in this article, comments are made on the nature of the S factor, comparing this dimension with both Eysenck's P factor and the dimensions Agreeableness and Conscientiousness, as proposed, for instance, in McCrae and Costa's version of Nor‐man's 5‐factor model. As against P, the S or Insensitivity factor seems to be only (negatively) related to Agreeableness and not to Conscientiousness. It is also argued that this finding seems to be in accord with the supposed schizoid nature of S and the criticisms levelled at Eysenck's EPQ‐P scale.

The dopamine transporter role in psychiatric phenotypes

The dopamine transporter (DAT) is one of the most relevant and investigated neurotransmitter transporters. DAT is a plasma membrane protein which plays a homeostatic role, controlling both extracellular and intracellular concentrations of dopamine (DA). Since unbalanced DA levels are known to be involved in numerous mental disorders, a wealth of investigations has provided valuable insights concerning DAT role into normal brain functioning and pathological processes. Briefly, this extensive but non-systematic review discusses what is recently known about the role of SLC6A3 gene which encodes the dopamine transporter in psychiatric phenotypes. DAT protein, SLC6A3 gene, animal models, neuropsychology, and neuroimaging investigations are also concisely discussed. To conclude, current challenges are reviewed in order to provide perspectives for future studies.

Dimensional Theory Applied to Schizophrenic Patients

Psychoticism, neuroticism, and extraversion are the dimensions of personality resulting from the statistical analysis of a number of psychological tests. Those working in this field state that the “isolation of three main dimensions—neuroticism, psychoticism, extraversion—may be said to have been accomplished at a reasonably high level of confidence” (Eysenck, 1952, p. 293). It has been stated also that these dimensions are relatively independent of one another and all independent of intelligence. In developing the dimensional picture of personality, tests which discriminated between a group of neurotic patients and a group of normals were found to inter-correlate positively and to generate a factor of neuroticism. Similarly tests were developed which distinguished between psychotic patients and normals, and between extraverts and introverts. To the writers' knowledge however there is no study available which applies the tests for all four dimensions to the same group of people. The four orthogonal dimensions should be identifiable, and would confirm the dimensional theory.

The effect of stimulus strength on binocular rivalry rate in healthy individuals: Implications for genetic, clinical and individual differences studies

Binocular rivalry (BR) occurs when conflicting images concurrently presented to corresponding retinal locations of each eye stochastically alternate in perception. Anomalies of BR rate have been examined in a range of clinical psychiatric conditions. In particular, slow BR rate has been proposed as an endophenotype for bipolar disorder (BD) to improve power in large-scale genome-wide association studies. Examining the validity of BR rate as a BD endophenotype however requires large-scale datasets (n=1000s to 10,000s), a standardized testing protocol, and optimization of stimulus parameters to maximize separation between BD and healthy groups. Such requirements are indeed relevant to all clinical psychiatric BR studies. Here we address the issue of stimulus optimization by examining the effect of stimulus parameter variation on BR rate and mixed-percept duration (MPD) in healthy individuals. We aimed to identify the stimulus parameters that induced the fastest BR rates with the least MPD. Employing a repeated-measures within-subjects design, 40 healthy adults completed four BR tasks using orthogonally drifting grating stimuli that varied in drift speed and aperture size. Pairwise comparisons were performed to determine modulation of BR rate and MPD by these stimulus parameters, and individual variation of such modulation was also assessed. From amongst the stimulus parameters examined, we found that 8cycles/s drift speed in a 1.5° aperture induced the fastest BR rate without increasing MPD, but that BR rate with this stimulus configuration was not substantially different to BR rate with stimulus parameters we have used in previous studies (i.e., 4cycles/s drift speed in a 1.5° aperture). In addition to contributing to stimulus optimization issues, the findings have implications for Levelt's Proposition IV of binocular rivalry dynamics and individual differences in such dynamics.

The Retardation Factor in Depression

Three groups of Ss, normal controls, severely depressed and mildly depressed, were compared on several objective tasks. Only the speed of perception of three dimensional objects differentiated satisfactorily between the groups. It was concluded that severely depressed Ss differed from both normals and mildly depressed Ss on the complex speed tasks.

A bright side, facet analysis of histrionic personality disorder: the relationship between the HDS Colourful factor and the NEO-PI-R facets in a large adult sample

This study looks at "bright-side," Big Five Personality trait correlates of a "dark-side" Personality Disorder, namely Histrionic Personality Disorder (HPD). More than 5000 British adults completed the Neuroticism Extraversion Openness Personality Inventory-Revised (Costa & McCrae, 1985), which measures the Big Five Personality factors at the Domain (Super Factor) and the Facet (Factor) level, as well as the Hogan Development Survey (HDS; Hogan & Hogan, 2009), which has a measure of HPD, exclusively called "Colourful" in the HDS terminology. Correlation and regression results confirmed many of the associations between these "bright" and "dark" side individual difference variables. The Colourful (HPD) score from the HDS was the criterion variable in all analyses. Colourful individuals are high on Extraversion and Openness, but also Stable and disagreeable. The Facet analysis identified Assertiveness and Immodesty as particularly characteristic of that type. The study confirmed work on HPD using different population groups and different measures, showing that personality traits are predictable and correlated with various personality disorders.

Seeing through the eyes of anxious individuals: an investigation of anxiety-related interpretations of emotional expressions

The interpretation of emotional states is necessary for successful social communication. Often individuals interpret emotional expressions intuitively and without full cognitive awareness. The aim of the present study was to test whether anxiety would influence affect interpretation in the manner suggested by interpretation bias-the tendency to interpret ambiguous cues in a threatening way. Interpretation of social cues was assessed with the similarity rating task (simtask) in two studies (n1 = 116, n2 = 76). The similarity ratings were analysed with a multidimensional scaling (MDS) approach, and the effects of anxiety on the interpretation of emotional expressions were analysed with multilevel modelling. The results of both studies showed evidence for an anxiety-related interpretation bias. High-anxious individuals tended to interpret milder threats as more negative than low-anxious individuals did. The consequences for anxiety research are discussed.

A bright side facet analysis of borderline personality disorder

BACKGROUND

This study looks at the "bright-side" normal, personality trait correlates of the "dark-side" Borderline Personality Disorder (BPD).

METHODS

Over 5000 British adults completed the NEO-PI-R which measures the Big Five Personality factors at the Domain and the Facet level, as well as the Hogan Development Survey which has a measure of Borderline Personality Disorder (BPD) called Excitable.

RESULTS

Correlation and regression results confirmed many of the associations between these "bright" and "dark" side individual difference variables. The Excitable score from the HDS was the criterion variable in all analyses. Excitable individuals are high on Neuroticism, but also Introverted and Disagreeable. The facet analysis identified Angry Hostility, Anxiety, Depression and Vulnerability as particularly characteristic of that type.

CONCLUSIONS

The study confirmed work on BPD using different population groups and different measures, showing that it is possible to describe personality disorders in terms of extreme scores on personality traits.

Ambient GABA Responsible for Age-Related Changes in Multistable Perception

Multistable perception is a psychophysical phenomenon in which one unique interpretation alternates spontaneously every few seconds between two or more interpretations of the same sensory input. Well-known examples include the Necker cube and face-vase illusions in vision. Interestingly, young adults generally see more perceptual switches than do elderly people. To understand the underlying neuronal mechanism of age-related multistable perception, we simulated a cortical neural network model that consists of multiple cell assemblies. In the network, a specific population of noncore cells and a common population of core cells form a cell assembly that represents a single object (or event). Every dynamic cell assembly, activated by a given sensory input, involves the common (overlapping) population of core cells. Ambient GABA-mediated intracortical tonic inhibition via extrasynaptic GABAa receptors destabilized the currently appearing dynamic cell assembly and terminated its burst firing. This allowed another dynamic cell assembly to emerge one after the other. Namely, multistable perception took place. Transporters, which were embedded in axon terminal membranes of interneurons, regulated levels of ambient GABA. For elderly people, we assumed a decline in transporter. This decelerated GABA augmentation and resulted in prolonging the durations of burst firing and thus in slowing perceptual switches. We suggest that poor control of ambient GABA levels due to age-related decline in GABA transporter may be responsible for the slowing of perceptual switches in elderly people.

Personality and Psychopathology: a Theory-Based Revision of Eysenck's PEN Model

The principal aim of this paper is to investigate whether it is possible to create a personality taxonomy of clinical relevance out of Eysenck's original PEN model by repairing the various shortcomings that can be noted in Eysenck's personality theory, particularly in relation to P or Psychoticism. Addressing three approaches that have been followed to answer the question 'which personality factors are basic?', arguments are listed to show that particularly the theory-informed approach, originally defended by Eysenck, may lead to scientific progress. However, also noting the many deficiencies in the nomological network surrounding P, the peculiar situation arises that we adhere to Eysenck's theory-informed methodology, but criticize his theory. These arguments and criticisms led to the replacement of P by three orthogonal and theory-based factors, Insensitivity (S), Orderliness (G), and Absorption (A), that together with the dimensions E or Extraversion and N or Neuroticism, that were retained from Eysenck's PEN model, appear to give a comprehensive account of the main vulnerability factors in schizophrenia and affective disorders, as well as in other psychopathological conditions.

The Cardiff Anomalous Perceptions Scale (CAPS): a new validated measure of anomalous perceptual experience

The study describes the Cardiff Anomalous Perceptions Scale (CAPS), a new validated measure of perceptual anomalies. The 32-item CAPS measure is a reliable, self-report scale, which uses neutral language, demonstrates high content validity, and includes subscales that measure distress, intrusiveness, and frequency of anomalous experience. The CAPS was completed by a general population sample of 336 participants and 20 psychotic inpatients. Approximately 11% of the general population sample scored above the mean of the psychotic patient sample, although, as a group, psychotic inpatients scored significantly more than the general population on all CAPS subscales. A principal components analysis of the general population data revealed 3 components: "clinical psychosis" (largely Schneiderian first-rank symptoms), "temporal lobe disturbance" (largely related to temporal lobe epilepsy and related seizure-like disturbances) and "chemosensation" (largely olfactory and gustatory experiences), suggesting that there are multiple contributory factors underlying anomalous perceptual experience and the "psychosis continuum."

Spatial- versus object-oriented architectural environments: preference and perception

This study examined changes in perceptual response and preference a specific category of architectural environment by age groups. Understanding relationships among age, perception, and preference is important in creating more appropriate environments. The hypothesis was that individuals who score field-dependent on an Embedded Figures Test would prefer architectural environments which support spatial orientation, while individuals who are field-independent would prefer environments without information on spatial organization or an object-oriented space. It was also hypothesized that children and elderly persons would score more field-dependent and prefer spatially orienting spaces. 64 subjects ages 4 to 85 years were recruited from local schools, various organizations for seniors and adults, given the Embedded Figures Test to measure field dependence, and were compared. Their scores were compared by preference for one of the two environments. Hypotheses were not supported for the spaces overall, however, clear patterns regarding seating preference were identified. Children and seniors had significantly more field-dependent preferences.

Latent inhibition deficits in high-schizotypal normals: symptom-specific or anxiety-related?

Latent inhibition (LI) is the phenomenon in which subjects who have repeatedly experienced an irrelevant stimulus perform more poorly on a new learning task with that stimulus than with a novel stimulus, presumably because of a decline in stimulus-specific attention. The present article reviews the literature on LI deficits in high-schizotypal normal subjects and schizophrenic patients. Although LI-deficits have been thought to be specific to these groups, evidence is presented that the effects may be related to the anxiety components of high-schizotypality and related pathologies.

Strauss (1969) revisited: a psychosis continuum in the general population?

Although dichotomously defined for clinical purposes, psychosis may exist as a continuous phenotype in nature. A random sample of 7076 men and women aged 18-64years were interviewed by trained lay interviewers with the Composite International Diagnostic Interview (CIDI). Those with evidence of psychosis according to the CIDI were additionally interviewed by psychiatrists. For the 17 CIDI core psychosis items, we compared a psychiatrist's rating of hallucinations and/or delusions (Clinical Psychosis; sample prevalence 4.2%) with three other possible positive CIDI ratings of the same items: (i) symptom present, but not clinically relevant (NCR Symptom; sample prevalence 12.9%); (ii) symptom present, but the result of drugs or somatic disorder (Secondary Symptom; sample prevalence 0.6%); (iii) symptom appears present, but there is a plausible explanation (Plausible Symptom; sample prevalence 4.0%). Of the 1237 individuals with any type of positive psychosis rating (sample prevalence 17.5%), only 26 (2.1%) had a DSM-III-R diagnosis of non-affective psychosis. All the different types of psychosis ratings were strongly associated with the presence of psychiatrist-rated Clinical Psychosis (NCR Symptom: OR=3.4; 95% CI: 2.9-3.9; Secondary Symptom: OR=4.5; 95% CI: 2.7-7.7; Plausible Symptom: OR=5.8; 95% CI: 4.7-7.1). Associations with lower age, single marital status, urban dwelling, lower level of education, lower quality of life, depressive symptoms and blunting of affect did not differ qualitatively as a function of type of rating of the psychotic symptom, were similar in individuals with and without any CIDI lifetime diagnosis, and closely resembled those previously reported for schizophrenia. Presence of any rating of hallucinations was strongly associated with any rating of delusions (OR=6.7; 95% CI: 5.6-8.1), regardless of presence of any CIDI lifetime diagnosis. The observation by Strauss (1969. Hallucinations and delusions as points on continua function. Arch. Gen. Psychiatry 21, 581-586) that dichotomously diagnosed psychotic symptoms in clinical samples are, in fact, part of a continuum of experiences, may also apply to the general population. The boundaries of the psychosis phenotype may extend beyond the clinical concept of schizophrenia.

Dynamical aspects of motor and perceptual processes in schizophrenic patients and healthy controls

The present study examined the temporal stationarity of the performance of 16 schizophrenic patients and 16 controls matched for age and sex in a bimanual coordination task and a perceptual task. In the motor task, rhythmic finger oscillations (alternating activity of homologue muscle groups) at increasing speed levels resulted in two measures, the preferred oscillation frequency and the critical frequency at which phase transitions (change towards simultaneous activity of homologue muscle groups) occurred. A measure of local dimensional complexity (pointwise D2 or PD2), which is a measure of non-linear dynamics, was determined for the acceleration profiles of the subjects' movements. Schizophrenics exhibited less stable movement dynamics than controls in horizontal finger cycling, indicated by a lower ratio critical/preferred frequency (critical ratio) and by higher means and standard deviations of the pointwise D2. In vertical cycling, the critical ratio did not differentiate between groups, while PD2 means and standard deviations did. Groups also differed specifically in perception of two ambiguous figures (Schroeder stairs and Rubin vase). Schizophrenics showed significantly higher reversal rates for the Rubin vase and a differential perceptive in comparison to controls in the perception of the Schroeder stairs. Measures of perceptual and motor stability were unrelated, which suggests that perceptual and motor processes are not influenced by a common underlying mechanism.

Physiological responses in high-P subjects during active and passive coping

There have been relatively few studies of the psychophysiological correlates of Eysenck's dimension of psychoticism (P) and those which do not exist report findings which cannot be readily integrated to isolate a distinctive physiological basis of P. The present study investigated differences between subjects scoring high and low on the P scale of the Eysenck Personality Questionnaire (EPQ) in relation to sympathetic and parasympathetic arousal following aversive stimulation. An active-passive coping paradigm using an aversive tone was selected to elicit responses and cardiovascular measures (heart period, heart period variance, T-wave amplitude) and a skin conductance measure (event-related skin conductance) were obtained. The findings show that differences between high- and low-P subjects are specific to the coping condition. Under active coping, high-P subjects exhibited greater sympathetic arousal following the aversive tone than low-P subjects. There was no significant difference between the high-P and low-P subjects on any physiological variable under the passive coping condition. It is suggested that if there is differential functioning of the divisions of the autonomic nervous system in subjects differing in P, that these differences may only manifest themselves under specific situations.

What is schizophrenia? Changing perspectives in epidemiology

The psychotic syndrome at the core of schizophrenia appears to be invariable across cultures. The risk of morbidity also seems to vary very little from country to country and over medium periods of time. Moreover, apart from gender differences in first onset, the cumulative lifetime risk is the same in females and males. A similar epidemiological pattern is only found in pathological conditions that are characterized by a precisely defined section of a psychopathological dimension with a continuous distribution in the population, e.g. severe mental retardation being the extreme section of normally distributed IQ values. The interpretation of schizophrenic psychosis as the extreme section of a psychopathological dimension or disposition that is almost evenly distributed in all populations is supported by the fact that milder psychiatric disorders occur more frequently before the onset of the psychosis and in close relatives of schizophrenic patients. The psychopathological heterogeneity of these disorders argues against the assumption of a manifest psychopathological dimension with a continuous transition from the schizophrenic psychosis to the "normal" schizothymic personality. More probable is a continuously distributed latent vulnerability to schizophrenia--with or without a threshold effect--which in severe degrees disposes to the uniform reaction pattern of the schizophrenia syndrome. Smaller degrees of vulnerability are associated with an increased risk for milder patterns of disturbances, which are also more strongly determined by environment and personality and therefore are rather heterogeneous. These assumptions lead to other epidemiological and genetic models than Kraepelin's early concept of a disease entity does.

Effects of chlorpromazine and promazine on the perception of some multi-stable visual figures

Chlorpromazine (CPZ) and promazine were studied for their effects on the reversal rate and dominance of aspect of several multi-stable (ambiguous) visual figures. The normal perception of some versions of the Schröder Staircase and the Man/Woman figure was biased towards one aspect and CPZ increased this bias compared with saline and promazine. There was a tendency for both CPZ and promazine to lower reversal rate. The results are discussed in relation to explanations of perceptual reversal and some implications are suggested for understanding the functional deficits of schizophrenia.

Psycholinguistic aspects of pauses and temporal patterns in schizophrenic speech

Schizophrenic speech was investigated at the moment of reading aloud paragraph-long stories and retelling them. Twenty white schizophrenic patients, with at least a high school diploma, were matched with 20 normals on the basis of race, educational level, sex, and age. Silent pauses (duration, frequency, and location), utterances (duration and syllable lengths, speech and articulation rates), and spoken hesitations (frequency and syllable lengths) were measured. When the semantic content of the stories did not agree with commonly held presuppositions, the speech characteristics of normals were analogues of the schizophrenic thought disorder.

[Effects of (--)delta-9-trans-tetrahydrocannabinol (delta-9-THC) on tests of psychoticism. A study of Eysenck's drug postulate on the effects of hallucinogens in relation to psychoticism (author's transl)]

In a double-blind study on 36 volunteers the effects of 250 mug/kg (--)delta-9-trans-tetrahydrocannabinol p.o. on objective and performance tests measuring psychoticism according to Eysenck were assessed. The hypothesis was tested that subjects treated with delta-9-THC differ from those receiving placebo in the same way as endogenous psychotics differ from normals. Confirmation was obtained in only 5 out of 19 variables. Four of these 5 variables may be considered as tests of concentration.

The personality of female prisoners

The theory has been put forward inCrime and Personality(Eysenck, 1964) that criminals are characterized by a combination of extraverted and neurotic personality traits; put in operational terms, it was suggested that compared with a control group of normal (non-criminal) subjects they would have higher scores on the N and E scales of the MPI or the EPI (Eysenck, 1959; Eysenck and Eysenck, 1964). In the second edition of the book the further hypothesis was added that prisoners would also be characterized by high P scores; the letter P refers to a third dimension of personality provisionally entitled ‘psychoticism’. Earlier investigations of the N x E hypothesis have been reviewed in the second edition ofCrime and Personality(Eysenck, 1970) and by Passingham (1972); the most recent study of both hypotheses is contained in two papers dealing with the personality makeup of male prisoners (Eysenck and Eysenck, 1970, 1971). The conclusions to be drawn from an examination of the literature are as follows: (1) As far as P is concerned, prisoners undoubtedly have much higher scores than do various types of control groups. (2) As far as N is concerned, most studies show prisoners to have significantly higher scores than controls. (3) As far as E is concerned, it appears that scores sometimes do and sometimes do not separate prisoners and controls in the predicted direction; it seems that we must distinguish between the two main components of E, i.e. sociability and impulsivity (Eysenck and Eysenck, 1969). Prisoners are significantly more impulsive, but less sociable, than controls.

Language structure and predictability in overinclusive patients

Deviant language behaviour is the primary basis for the clinical inference of thought disorder. Bleuler (1950), for example, emphasizes loose associations and disjointed utterances. Mayer-Gross, Slater, and Roth (1960) state that thought disorder is indicated by such conversation characteristics as ‘woolly vagueness', in-consequential following of side issues, direction by alliteration, analogies or clang associations, and the use of words out of context. However, psychological studies have typically used measures of disordered thinking derived from performance on categorization tasks. Such tasks do not obviously measure the abnormality which is definitive for the clinician. The study reported here was an attempt to relate measures of language effectiveness to overinclusive thought disorder.

Severity and type of psychotic illness as a function of personality

Eysenck (1952a) has postulated the existence of three main dimensions of personality: Extraversion, Neuroticism and Psychoticism. These are conceived of as independent of each other, and as continuous, with neurotics and psychotics respectively marking the extreme ends of the N and P dimensions. Within each dimension, the particular type of neurotic or psychotic illness is considered to be determined by the degree of extraversion of the patient; thus dysthymic and hysterical disorders mark the introverted and extraverted types of neurotic illness (Eysenck, 1947), while within the psychotic field degree of social withdrawal might be considered to be the variable most closely related to introversion/ extraversion (Venables and Wing, 1962). Hypotheses have also been formulated to account for the causal factors underlying E and N (Eysenck, 1967), although no such hypotheses have been elaborated with respect to P. A special statistical technique (criterion analysis—Eysenck, 1950) has been worked out to test the crucial question of continuity between normal and abnormal (neurotic and psychotic) populations with respect to N and P; application of this method has given support to the theory of continuity (Eysenck, 1950, 1952b).

The questionnaire measurement of psychoticism

A study is reported of a random sample of 170 normal men and 192 normal women who were given a 110-item questionnaire incorporating items intended to measure personality variables P (psychoticism), N (neuroticism), E (extraversion), and L (a lie and dissimulation scale). Factor analysis of the intercorrelations between items disclosed a clear-cut psychoticism factor, relatively independent of the others. The rationale and the psychiatric importance of this factor are discussed.