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Biomedical subjects

G Claridge

Publications and source records attributed to G Claridge.

At least 19 recordsLinked to original sources
PubMed2001

Schizotypy and the shift from dextrality: a study of handedness in a large non-clinical sample.

Numerous previous studies have reported associations between schizophrenia/schizotypy and atypical handedness. While there is broad agreement that schizophrenia/schizotypy is associated with a shift away from typical (strong right) handedness, it is not entirely clear what aspect of atypical handedness is implicated: 'ambiguous' handedness (the absence of hand preference for given actions) or 'mixed handedness' (different hand preferences for different actions). The present study used several indices of handedness (derived from the Annett scale) to address these questions in 3000 + (mostly) University student subjects recruited by electronic mail. It was found that positive schizotypy (indexed by a scale of 'unusual experiences') was associated with both aspects of atypical handedness. These findings are discussed in the light of various possible explanations of the association between handedness and schizophrenia/schizotypy.

Adolescent↗
PubMed2000

Not just a pretty face: physical attractiveness and perfectionism in the risk for eating disorders.

OBJECTIVE: Considerable research has examined the correlates and consequences of both objective and subjective ratings of physical attractiveness. Numerous studies have found, for example, that subjective physical attractiveness is inversely related to weight and diet concerns. Surprisingly, however, no research has examined the relationship between objective physical beauty and eating pathologies, despite clinical and theoretical reasons to expect a positive relationship between the two. METHOD: We rated 203 young women on facial attractiveness and obtained self-report measures of perfectionism, neuroticism, and weight preoccupation. RESULTS: Attractiveness was positively related to weight preoccupation after controlling for body size and neurotic perfectionism. DISCUSSION: These findings provide the first evidence of physical beauty as a risk for disordered eating, and confirm earlier evidence that the relationship between general perfectionism and disordered eating only occurs when combined with a tendency to be anxious and hypercritical. Results are discussed in the context of identity formation and the attractiveness stereotype.

Adult↗
PubMed1998

Schizophrenia risk and handedness: a mixed picture.

Numerous previous studies have reported on handedness differences among schizophrenics, as well as in normal subjects who are high in ''schizotypal'' traits, and hence putatively at risk for schizophrenia. Results have varied, but there is evidence of a shift away from dextrality, especially consistent among schizotypal individuals. Using both a conventional three-category and Annett's seven-category classification of handedness, we re-examined the question in 681 general population subjects assessed for schizotypy. The three-category analysis confirmed previous findings of increased schizotypy in mixed-handers. However, the more fine-grained analysis showed that, although mild degrees of mixed handedness were indeed associated with increased schizotypy, this trend was reversed in the most mixed-handed subjects whose schizotypy scores did not differ significantly from right-handers. Independently of our work, this subgroup of mixed-handers are also reported to show superior intellectual function, especially on some spatial tasks. We concluded that previous studies of schizophrenia and schizotypy have failed to distinguish different reasons for shifts from dextrality. It is argued that the latter's association with schizophrenia might come about through exogenous, neurodevelopmental, influences, whereas some-possibly genetically basedforms of mixed handedness could reflect a variety of cerebral organisation that protects against, rather than enhances, the risk for mental disorder.

Journal Article↗
PubMed1997

Electrodermal relationships with personality measures of psychosis-proneness in psychotic and normal subjects.

The relationships between several indices of psychosis proneness and bilateral electrodermal orienting were examined in a large group of normal subjects and a heterogeneous group of schizophrenic patients. In the normal group, the Cognitive Disorganisation scale was characterised by shorter latencies and more irregular patterns of responding that may indicate greater disinhibitory processing in the regulation of attentional mechanisms. The Unusual Experiences scale and paranoia (both measures of positive or 'active' schizotypy) were associated with a predominance of left hemisphere influences in normal female controls. High Introvertive Anhedonia scores predicted non-responding status in schizophrenic patients and hypo-responsivity in normal controls in support of some previous studies. Overall the results support the specificity and validity of different measures of psychosis proneness and the utility of psychophysiological investigation beyond the psychotic disorders themselves.

Adult↗
PubMed1997

Nightmares, dreams, and schizotypy.

The theory that psychosis and dreaming share some common underlying mechanism finds support in the observation that chronic nightmare sufferers are at increased risk for psychopathology. We examined this connection in a large general population sample, administering a battery of psychosis proneness and other personality scales, together with a nightmare distress scale; participants also answered a single question on pleasurable mood associated with dreaming. In addition, they completed the Bem Sex Role Inventory, to reinvestigate previously observed gender differences in nightmare susceptibility. It was found that, among the psychosis proneness scales, the best predictor of nightmare distress was STA, a mostly cognitive measure of schizotypy; this was true even after allowing for a strong influence in the data of general neuroticism. Other aspects of psychosis proneness--e.g. anhedonia--were unrelated to nightmares. However, sex and sex role differences did make a significant contribution, self-confessed feminine females and masculine males reporting, respectively, the highest and lowest nightmare distress. For schizotypy it was further shown that relationships were not confined to the nightmare experience; high (STA) schizotypes also significantly more often reported enjoyable dreaming. It was concluded that a unifying theme explaining the data is the schizotype's greater imaginativeness, which can have both positive and negative expression in sleep and consciousness.

Adolescent↗
PubMed1996

The factor structure of "schizotypal' traits: a large replication study.

The heterogeneity of schizotypal traits, suggested in previous research, was further investigated in a sample of subjects (N = 1095) administered a composite questionnaire consisting of a large number of published scales the majority of which were designed to measure psychotic characteristics. Factor analysis confirmed the four components previously indicated in our work with the same instrument; namely, "aberrant perceptions and beliefs', "cognitive disorganization', "introvertive anhedonia' and "asocial behaviour'. This structure was maintained regardless of whether or not the analysis included scales from the Eysenck Personality Questionnaire, which might otherwise have been held to explain the variance. "Aberrant perceptions and beliefs'-reminiscent of the positive symptoms of schizophrenia-was the strongest component; but, given the multidimensional nature of the data, together with the pattern of factor loadings and intercorrelations for the scales involved, it was concluded that the broader term "psychosis-proneness' or "psychoticism' (in a non-Eysenckian sense) might be a better descriptor of the clinical and personality domain sampled.

Adult↗
PubMed1995

Subject matter and poetic devices in psychotics' poetry.

It has long been supposed that there is a connection between the mental processes of psychosis and those of creativity. The present study aimed to investigate this idea by means of a comparison between the poetic output of psychotics and that of normals, taking as its starting-point the notion that if there are observable differences between these two groups in terms of subject matter and linguistic features, this would suggest that creativity and psychosis are not to be identified with each other. Eighty poems by contemporary, non-professional poets (40 by psychotics and 40 by normals) were analysed on 11 different dimensions. The two samples of poems were highly similar on most of the dimensions investigated. The main differences found were in the incidence of self-analysis as a theme, reference to proper names and specific locations, and in the proportion of metaphors which fell into the category 'psychological/physical'. The two latter differences appeared to be largely a product of the first. It was concluded that although 'normal' and 'psychotic' poetic activities are not identical, they are closely related. This may be either because general poetic creativity does have psychotic features, or because the poetic function of language was relatively spared in at least this sample of psychotics.

Case-Control Studies↗
PubMed1994

Single indicator of risk for schizophrenia: probable fact or likely myth?

The longitudinal followup strategy in high-risk research is being increasingly complemented by the use of psychosis-proneness scales to select subjects for study who might be vulnerable to schizophrenia and who show differences on laboratory measures that could act as endophenotypic markers for use in genetic investigations. Three types of experimental paradigm have been adopted, drawn from cognitive psychology, psychophysiology, and the neuropsychology of hemisphere function. Results adopting each of these approaches are examined, alongside recent factor-analytic evidence that psychosis-proneness scales currently in use tap up to four different components that map onto the clinical heterogeneity of schizophrenia (and possibly other forms of psychosis). No one of these components clearly emerges as, or points to, a single indicator of risk, though some aspect of neurocognitive functioning seems a likely candidate. Even so, it is argued, the clinical expression of vulnerability must be due to a convergence in an individual of several components of risk since individually (and notably so for "susceptibility to positive symptoms") they are very common in the healthy population. In evaluating the evidence, attention is drawn to two crucially different ways that investigators in schizophrenia research have construed the notion of continuity (1) as subclinical defect (or forme fruste of disease) having varying expression or (2) as biologically based personality dimensions that simultaneously describe the dispositions to aberrations of function leading to degree of illness. It is noted that the model of continuity chosen can significantly shape the way the results of risk research are interpreted and the theories of psychosis to which they give rise.

Genetic Markers↗
PubMed1991

Reliability and validity of a psychotic traits questionnaire (STQ).

The 'schizotypal personality' (STA) and 'borderline personality' (STB) scales of the STQ were administered to two groups: normal subjects who had completed the questionnaire on a previous occasion, four years earlier, and a 'clinical' sample, consisting of members of a self-help support group for people who at some time in the past had been psychiatrically diagnosed as suffering from a psychotic illness, mainly schizophrenia. As predicted, the latter had significantly higher scores than controls on both STQ scales, certain items also being particularly discriminating. Within the control group a test-retest analysis revealed correlations which, depending on scale and gender, were around .60. It was concluded that the STQ is a valid measure of psychotic traits and that scores on the questionnaire have good long-term stability. The results are discussed against the background, and in support of, a continuity view of psychosis.

Adult↗
PubMed1989

Evidence of reduced 'cognitive inhibition' in schizophrenia.

An experiment is described which investigated cognitive inhibition in schizophrenia. It is noted that both the abnormal and cognitive literatures use the concept of inhibition. Frith (1979) suggests that the more cognitive symptoms of schizophrenia may be due to the failure to limit the current contents of consciousness due to a failure adequately to inhibit the output of preconscious processes. Current thinking in cognitive psychology suggests that in the process of selective attention there is active inhibition of distractor information. A technique used to investigate this is termed negative priming (Tipper, 1985). The general nature of this paradigm is as follows: if a distractor, which has been previously ignored, is response, due to inhibition of the information when it was originally a distractor. It was found that inhibition of such distracting information was reduced in schizophrenics. This finding is seen as providing some support for Frith's (1979) theory that the cognitive symptoms of schizophrenia are due to awareness of processes that normally occur preconsciously.

Adult↗
PubMed1989

Individual differences in schizotypy as reflected in measures of cognitive inhibition.

Three experiments are reported using the 'negative priming' paradigm to investigate cognitive differences in normal schizotypal subjects. Lists of Stroop colour words were presented at different display times in a number of priming and non-priming conditions, in one of which the ignored colour name predicted the colour of the next target item. The increased RT latencies to the target normally found in this condition were reduced, or even reversed, in high schizotypal subjects selected on the basis of a new schizotypy scale (STA). This effect was confined to a very short presentation time (100 ms), suggesting that schizotypy is associated with weakened inhibition operating in the early (automatic) stages of information processing. The familiar Stroop (interference) effect was related overall to negative priming, but was not responsible for the schizotypy differences.

Adolescent↗
PubMed1987

Individual differences in negative priming: relations with schizotypal personality traits.

A study is reported of normal subjects, selected for degree of schizotypal personality traits, on a cognitive task designed to measure, in a negative priming paradigm, the extent to which they differed in interference and presumed inhibitory effects on performance. The main individual differences measure used--a new scale of schizotypy--showed, as predicted, a significant correlation with negative priming. The correlation with a measure of 'interference' was non-significant but in the expected direction. The results are judged relevant to research implicating a weakening of inhibitory selective mechanisms in schizophrenia and to models in abnormal psychology proposing a continuum between normal and abnormal cognitive function. As such, they suggest a soundly based theoretical approach to the analysis of the individual variations in information processing commonly observed in general cognitive psychology.

Adult↗
PubMed1987

'The schizophrenias as nervous types' revisited.

In 1972 the author proposed that schizophrenia represents an aberration of central nervous processes that underlie cognitive and personality characteristics which can be observed in many healthy people. The present paper brings the evidence for that theory up to date and concludes that over the past 15 years it has received considerable empirical support. The way in which the theory confronts the question of whether or not schizophrenia is a disease is also clarified.

Brain↗
PubMed1982

Covariation between two-flash threshold and skin conductance level in first-breakdown schizophrenics: relationships in drug-free patients and effects of treatment.

Earlier research suggested that, compared with other individuals, schizophrenics show a different form of covariation between electrodermal level and perceptual discrimination, as indexed by the two-flash threshold. However, dispute has arisen as to whether previous contradictory results obtained on patient samples can be explained by a conventional inverted-U function or whether the relationship takes on an entirely different form, i.e., a U function. The latter alternative was confirmed here in a study of first-breakdown drug-free schizophrenics, tested on 3 consecutive days after hospital admission and before treatment began. However, the U function was evident only in the larger of two subgroups of schizophrenics, identified as patients whose treatment was delayed longer after admission, who were clinically less emotionally responsive and who, in basic personality, were more introverted. When the patients were subsequently tested during treatment, no systematic relationship between two-flash threshold and skin conductance could be discerned. The latter presumably reflected the fact that, during this phase of the experiment, there were marked and complex changes in the individual measures, the effects of treatment on which were briefly examined.

Adolescent↗
PubMed1978

Animal models of schizophrenia: the case for LSD-25.

Some of the difficulties of trying to establish an animal model of schizophrenia are first considered. Then, after a review of the evidence on the experimental psychopathology of schizophrenia, particularly that concerned with attention and arousal, it is concluded that the core feature which needs to be modeled in animals is some aspect of "input dysfunction." It is argued that, of the pharmacological strategies, LSD-25 comes nearest to meeting that requirement, for two reasons. First, the phenomenology of an LSD "model psychosis" closely parallels that of the natural disease. Secondly, the experimental effects of the drug, both in animals and man, are very similar to or can be closely aligned theoretically with those of schizophrenia. An example is quoted from work in the author's laboratory where LSD was found to produce psychophysiological effects virtually identical to those observed occurring naturally in acute psychotic patients and in normal subjects high in "psychotic" personality traits. It is suggested that the rejection of LSD as a drug model was premature, especially as the currently popular preference for amphetamine has not been vindicated, either by the latter's ability to mimic an important central feature of the psychotic state or by work on dopamine as a specific common mediator of amphetamine psychosis and of schizophrenia.

Animals↗