Gordon Claridge

Schizotypy and hemisphere function—I: Theoretical considerations and the measurement of schizotypy

Abstract This paper brings together, in the context of individual-differences theory, two developing themes in schizophrenia research. One concerns the manifestation, in normal people, of ‘psychotic’ characteristics and their measurement using scales which, unlike the Eysenck P scale, draw their items from the clinical symptomatology of psychosis. Recent work on the so-called ‘borderline states’ is considered especially relevant and a new two-scale questionnaire (STQ) is described which was modelled on the current distinction, in DSM-III, between ‘schizotypal personality disorder’ and ‘borderline personality disorder’. The second theme addressed concerns the possible biological basis of individual differences in ‘schizotypy’. It is argued, in the light of some emerging views about the nature of schizophrenia, that this may lie in the functional and structural properties of hemisphere organization. A suggested strategy for evaluating this theory is an examination of the performance of schizotypal normal Ss on tests of hemisphere function.

New scales for the assessment of schizotypy.

Abstract This study reports the development of new scales for assessing schizotypal traits. The four scales measure unusual experiences, cognitive disorganisation, introvertive anhedonia and impulsive non-conformity. The scales were incorporated into a new questionnaire, the Oxford-Liverpool Inventory of Feelings & Experiences (O-LIFE), in a form designed for use in the normal population and including filler items as well as the STA scale (as a known referent). Norms for the scales on a fresh sample of normal subjects (N = 508) are reported, including sex and age differences. All the scales were found to have adequate internal consistency (coeff. alpha s> 0.77). The items from the four new scales were submitted to factor analysis and a highly similar structure resulted. Their present and future use in psychosis-proneness research is discussed.

The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE): Further description and extended norms

BACKGROUND The Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE) was introduced in 1995 as a four-scale questionnaire for measuring psychosis-proneness, principally schizotypy. Its items were deliberately chosen to make it suitable for tapping psychotic characteristics in healthy individuals. Since its inception the O-LIFE has been used in a wide variety of experimental and clinical studies, establishing its reliability and validity. METHODS Data was pooled from 1926 participants together with available demographic information from several research institutions. RESULTS Extensive norms are presented by age and gender. Inter-correlations and regression equations based on age and gender are also presented. CONCLUSIONS The theoretical background and implications of work on using the O-LIFE are briefly discussed.

Short scales for measuring schizotypy

BACKGROUND This study reports short scales for measuring several dimensions of schizotypy in the normal population based on a large twin sample. METHODS The four short scales use items drawn from a longer instrument, the Oxford-Liverpool Inventory of Feelings and Experiences. Using concordance estimates from MZ and DZ pairs, the items were selected both to have a high heritability and to offer broad coverage of each trait domain. RESULTS Preliminary descriptive statistics are reported for the short scales and suggest adequate reliability. CONCLUSIONS New scales offer a time efficient and reliable method of studying proneness to psychosis in large N designs.

Schizotypal Personality: Fully and quasi-dimensional constructions of schizotypy

This chapter concerns the dimensionality inherent to describe and understand schizotypy and schizotypal personality disorder (SPD). It concerns attempts that are being made to discover experimental paradigms to characterize the cognitive functioning of schizotypal and schizotypally disordered individuals; or, develop markers of cognitive nature that might be helpful in high-risk and genetics research. Two traditional views of dimensionality can be discerned, and roughly align to the psychiatric and psychological models. The psychiatric view of continuity is characteristically quasi-dimensional. Focusing on variations within the illness domain, and taking the abnormal state as its reference point, it construes dimensionality as degrees of expression of a disease process. Typical questions include diagnostic and nosological issues such as the relationship between full-blown psychosis and forms of personality disorder as possible formes frustes of disease: SPD in the case of schizophrenia. The fully dimensional takes normality or health as the starting point.

Healthy schizotypy: the case of out-of-the-body experiences

Abstract The present study tested the hypothesis that a group of normal subjects reporting at least one hallucinatory experience (an ‘out-of-the-body’ experience or OBE) could score highly on one of the factors of schizotypy without scoring highly on the rest. A total of 684 subjects were recruited, of whom 450 reported at least one OBE and 234 did not. They completed the Combined Schizotypal Traits Questionnaire of Bentall, Claridge, and Slade [Bentall, R. P., Claridge, G., & Slade, P. D. (1989). The multi-dimensional nature of schizotypal traits: a factor analytic study with normal subjects. British Journal of Clinical Psychology, 28, 363–375]. A number of discriminant analyses were carried out to compare different sub-groups of the OBErs with suitable controls, using the factor scores on four factors as predictors of group membership (OBErs versus non-OBErs). It was found that OBErs scored significantly higher than non-OBErs only on the first of the four factors, aberrant perceptions and beliefs, but not on the other three: cognitive disorganisation with social anxiety, introvertive anhedonia, and asocial schizotypy. The results are interpreted as supporting the idea of ‘healthy schizotypes’ who are functional in spite of, and even in part because of, their anomalous perceptual and other experiences. It is argued that this idea fits best with a fully dimensional model of schizotypy, independent of, although causally related to, the disease process of schizophrenia itself.

A biometrical study of schizotypy in a normal population

Abstract A recently devised two-scale questionnaire (STQ) for measuring ‘borderline’ personality traits, together with the EPQ, was administered to 108 monozygotic and 102 dizygotic adult twin pairs. Initial item and scale analyses of the STQ indicated good internal consistency and acceptably high endorsement frequencies for individual items, as well as an absense of any marked skew in the scale distributions. The pattern of correlations with the EPQ closely resembled that seen in earlier, smaller-sized studies, the most notable feature being a positive correlation between the borderline scales and the N-scale. Biometrical analysis of the data suggested that, for the main STQ scale (‘schizotypal personality’), the best-fitting model was one assuming additive genetic variation combined with within-family environmental effects: results for the other (‘borderline personality’) scale were less clear cut. A number of sex differences were also observed: males had lower schizotypy scores than females, while the biometrical analysis suggested that schizotypy may be under greater genetic control in males than in females. The data are presented and discussed in the context of the dimensional/biological theory of disposition to psychosis.

The factor structure of schizotypy in a normal population

Abstract Based on a sample of 420 adult subjects drawn from a population based registry, the factor structure of a schizotypal personality scale is reported. Males and females were analysed both separately and jointly by unweighted least squares analysis of the inter-item tetrachoric correlations. Although there was a clear general factor indexed by the overall scale, both analyses indicated 3 robust component factors which could readily be identified with “magical ideation”, “unusual perceptual experiences” and “paranoid ideation and suspiciousness” and which were indexed by subscales of 8 items each. Ideas of reference and social anxiety did not emerge as independent factors in this questionnaire scale. There is, however, a congruence between the 3 identified factors in this normal population with those corresponding DSM-III clinical criteria for schizotypal personality disorder which can be assessed by self report. These results give support for the dispositional hypothesis and further impetus for the development of self report scales of schizotypal personality disorder.

What's the use of neuroticism?

In this paper we examine two aspects of neuroticism (N): its status as a personality descriptor and its role in the personality dynamics of abnormal states. We first suggest that high N is such a universal accompaniment of abnormal functioning (both psychological and biological) that by itself it has little descriptive or explanatory value. Then, acknowledging that N has more utility when used alongside other personality variables, we argue that here the most informative are disorder-specific characteristics that have unique variance, while also correlating with N. We propose that Ns role in aetiology is that of a moderator variable, influencing the expression of these disorder-specific characteristics to produce (or not) the clinical conditions to which they relate. By way of illustration, examples are taken from our joint studies of the eating disorders and of schizotypy and schizophrenia.

Development of a version of the Schizotypy Traits Questionnaire (STA) for screening children.

Schizotypy may be seen as both a dimension of normal individual differences and an indicator of the predisposition to schizophrenia and schizophrenia-spectrum disorders. Schizotypal traits have been widely investigated in adults but little research has explored schizotypy in younger samples. The aim of the present study was to examine the factor structure of schizotypal traits in a sample of normal children aged 11 to 15 years-a younger sample than investigated in the few previous studies. Schizotypal traits were assessed with the childrens version of the adult Schizotypy Traits Questionnaire (STA). A principal components analysis was carried out on data from 317 subjects and yielded a three-factor solution, similar to several previous studies of adult samples. Factor one was characterised by unusual perceptual experiences, factor two by paranoid ideation/social anxiety, and factor three by magical thinking. The factor structure of the STA of this young sample was comparable with the previous studies of adults. The findings suggest that the childrens version of STA is a scale suitable for the measurement of schizotypy in young populations, and that this scale could be useful in clinical assessment of children at risk for psychosis, as well as in research.