Somatosensory processing in the biological relatives of schizophrenia patients: a signal detection analysis of two-point discrimination.

This study examined 2-point discrimination performance in 1 st-degree biological relatives (n = 39) of individuals with schizophrenia and normal adult control participants (n = 30) recruited from the community. They completed an objective 2-point discrimination task, adapted for use with a signal detection approach to permit separation of discriminability (i.e., sensitivity, d') from response bias/ criterion (or motivation, lnbeta). Relatives revealed poorer performance on the d' index compared with controls. The 2 groups did not differ on lnbeta, suggesting a genuine difference in sensitivity but not response bias. The sensitivity deficit might reflect decreased spatial acuity and/or impaired intensity cue processing of tactile stimuli. Poor performance on the d' index was most closely associated with 2 schizotypic features, namely "odd beliefs/magical thinking."

Reaction time slowing during high-load, sustained-attention task performance in relation to psychometrically identified schizotypy.

Prior research has demonstrated a reliable deficit in performance accuracy (e.g., d') on sustained-attention tasks in relation to psychometrically identified schizotypy and clinically diagnosed schizotypal psychopathology. The present study sought to expand the understanding of sustained-attention performance in relation to psychometric schizotypy through a study of reaction time (RT) performance. In this study, the author examined performance accuracy and RT on a high-load, sustained-attention task, the Continuous Performance Test-Identical Pairs (CPT-IP) version, in 31 high Perceptual Aberration Scale (PAS) and 26 normal control (control PAS) subjects from a large university population. High PAS (psychometric schizotypy) subjects displayed significantly longer RT performance on the CPT-IP relative to controls. The RT slowing was not explained by mental state or general intellectual ability factors. Contrary to expectation, a difference in performance accuracy (e.g., d') was not observed between the groups; however, power and other considerations cloud the interpretation of this finding. The meaning of the observed RT slowing is examined and its relation to current models of the development of schizophrenia is discussed.

The Inventory of Personality Organization: psychometric properties, factorial composition, and criterion relations with affect, aggressive dyscontrol, psychosis proneness, and self-domains in a nonclinical sample.

This report describes 2 studies of the psychometric characteristics of the primary clinical scales of the Inventory of Personality Organization (IPO; O. F. Kernberg & J. F. Clarkin, 1995), which assess reality testing, primitive psychological defenses, and identity diffusion, in a nonclinical sample. The 3 IPO scales display adequate internal consistency and good test-retest reliability. Item-level confirmatory factor analysis supported a two-factor structure of the IPO consistent with O. F. Kernberg's (1984, 1996) model of borderline personality organization. Each of the 3 IPO scales was associated with increased negative affect, aggressive dyscontrol, and dysphoria as well as lower levels of positive affect consistent with Kernberg's model of borderline personality organization. The IPO Reality Testing scale is closely related to various measures of psychotic-like phenomena.

Auditory working memory and verbal recall memory in schizotypy.

Deficits on verbal memory tasks, as well as on spatial and auditory working memory tasks, have been observed in schizophrenia patients. A useful strategy in the determination of the premorbid indicator status of specific cognitive and memory deficits observed in patients is to examine those persons at increased biological risk for schizophrenia (e.g. first-degree relatives), schizotypal personality disorder patients, and/or psychometrically identified schizotypes for comparable deficits, though perhaps less profound than those seen in actual patients. We examined verbal memory and auditory working memory functioning in 31 schizotypic and 26 normal control subjects from a large randomly ascertained non-clinical university population. Schizotypy status was determined psychometrically using the well-known Perceptual Aberration Scale. Contrary to our theory-guided expectations, noteworthy deficits in verbal memory and auditory working memory were not observed in the schizotypic subjects and the two experimental groups did not differ significantly on any of the memory measures. These results were discussed in light of prior results obtained using the spatial delayed response task (i.e. spatial working memory) and Wisconsin Card Sorting Test performance on these same subjects. The theoretical implications of these findings are discussed in relation to the putative processes involved in the working memory system, as well as in relation to the schizotypy construct.

Two-point discrimination thresholds and schizotypy: illuminating a somatosensory dysfunction.

The current study sought to determine if somatosensory deviations, assessed by determining two-point discrimination thresholds, were associated with schizotypic features in non-psychotic subjects (N=100). It was hypothesized that elevated two-point discrimination thresholds would be associated with an increased likelihood of higher levels of schizotypy features. The results of the study suggested that at the level of individual differences, higher two-point discrimination thresholds (ascending series assessments) were associated with higher levels of schizotypy as operationalized by several prominent measures of schizotypy. A deviant subgroup analysis clearly suggested that, for ascending series two-point threshold assessments, those persons requiring the greatest distance (i.e. highest thresholds) to detect two-point stimulation were substantially more schizotypic than a contrast group. Control analyses that focused on psychological state (depression, anxiety) and intellectual functioning variables revealed that these factors were, more or less, unrelated to two-point discrimination thresholds and they did not account for the observed significant relations between the schizotypy scales and two-point threshold values. The results of this study are discussed within a neuropsychological context implicating parietal cortex involvement with schizotypy and schizophrenia.

Taxonic structure of infant reactivity: evidence from a taxometric perspective.

Previously, we proposed a theoretical framework that classified infants into qualitative categories of reactivity, rather than on a continuous dimension. The present research used an objective statistical procedure (maximum covariance analysis, or MAXCOV) to determine if a qualitative latent structure, consistent with our theoretical conjectures, would be found to underlie quantitative indices of reactivity to stimuli in a sample of 599 four-month-old infants. Results of the MAXCOV analysis showed clear evidence of a latent discontinuity underlying the behavioral measures of infant reactivity. The base rate of the latent class (or taxon) was estimated at 10%. Infants within the putative high-reactivity taxon, compared with infants not in the taxon, were elevated on measures of behavioral inhibition at 4.5 years. These results provide objective empirical support for a central tenet in our theoretical model by supporting the taxonicity of infant reactivity.

Stability and change in personality disorder features: the Longitudinal Study of Personality Disorders.

BACKGROUND: There exists no empirical literature documenting the long-term longitudinal stability of personality pathology comparable to that available for normal personality. A number of test-retest studies have usefully established the short-term reliability of Axis II measures. However, the test-retest design is methodologically inadequate for resolving issues related to the long-term stability of personality disorder (PD). This prospective longitudinal study evaluated the stability of PD features in multiwave perspective. METHODS: Subjects (N = 250) drawn from a nonclinical university population were examined for PD features at 3 different time points using the International Personality Disorders Examination (IPDE) and the Millon Clinical Multiaxial Inventory II (MCMI-II) during a study period of 4 years. RESULTS: Features of PD displayed considerable evidence of stability for individual differences and group means, at the dimensional level of analysis, on both the IPDE and the MCMI-II. Both measures revealed modest declines in PD features over time; however, the observed changes were associated with relatively small effect sizes. CONCLUSION: Features of PD, viewed from a dimensional perspective, seem to be relatively stable in terms of individual differences and group means based on both clinical interview and self-administered PD assessments.

Schizophrenia: refining the phenotype, resolving endophenotypes.

The conceptual history of the diagnosis of schizophrenia is reviewed and the current definition of the illness is examined (e.g. DSM-IV). A dimensional alternative to the traditional categorical model of diagnosis is discussed with a specific emphasis on the four dimensions of psychopathology represented by reality distortion (hallucinations, delusions), disorganization (positive formal thought disorder, bizarre behavior), negative symptoms (flattened affect, avolition, alogia, asociality), and premorbid social functioning. Also discussed is the development of structured psychiatric interviews that emerged from the clinical/research context that gave rise to explicit (i.e. operational) diagnostic criteria for schizophrenia. The general methodological approach used to detect valid endophenotypes for schizophrenia liability--i.e. indicators of liability not visible to the unaided naked eye--as well as their potential diagnostic and research utility is presented in overview. The rationale for linking such indicators to schizophrenia liability, which is conceptualized as a latent construct, is also reviewed. Future directions in the development and refinement of the diagnostic approach to schizophrenia and schizophrenia liability are highlighted.

Deeper into the schizotypy taxon: on the robust nature of maximum covariance analysis.

Prior research has suggested that the latent structure of the schizotypy construct (P. E. Meehl, 1990) may be qualitative in nature and have a low base rate (L. Korfine & M. F. Lenzenweger, 1995; M. F. Lenzenweger & L. Korfine, 1992). These studies relied on the application of maximum covariance analysis (MAXCOV) to 8 true-false format items from a schizotypy measure. The current study sought to examine the robustness of those prior findings through MAXCOV analysis of fully quantitative measures of schizotypy. Measures of perceptual aberration, magical ideation, and referential thinking were analyzed using MAXCOV in a sample of 429 persons. The results of these analyses strongly support a latent taxonic structure for schizotypy and a low base rate for the schizotypy taxon. Furthermore, the members of the putative taxon reveal an increased level of deviance on a psychometric measure known to be associated with schizophrenia liability. The possibility that the dichotomous item format of those items analyzed previously with MAXCOV lead to spurious pseudotaxonicity is greatly diminished in light of these results.

Antisaccades and smooth pursuit eye tracking and schizotypy.

BACKGROUND: Eye tracking deficits are one of a few widely validated behavioral markers of risk for schizophrenia. Recently, it has been proposed that antisaccade performance may also constitute a marker of schizophrenia risk. This study investigated whether eye tracking and antisaccade deficits could be found in another population with putative liability to schizophrenia-nonclinical subjects with elevated scores on a psychometric index of perceptual aberrations. METHODS: Subjects were 55 university students who received either high or normal scores on the Perceptual Aberration Scale, a measure of schizotypy indexing body image and perceptual distortions. Subjects completed a smooth pursuit eye tracking task and an antisaccade task. Eye movements were monitored using an infrared limbus tracker. RESULTS: Subjects with high Perceptual Aberration Scale scores (putative "schizotypes") had lower pursuit quality and a lower percentage correct on the antisaccade task than the controls. The 2 groups did not differ in antisaccade or error latencies. The increase in antisaccade errors in the schizotypes was accounted for almost entirely by an increase in perseverative errors, but virtually no difference between groups on random errors. Antisaccade performance was significantly related to pursuit quality. CONCLUSIONS: Subjects with elevated Perceptual Aberration Scale scores have performance deficits on oculomotor tasks that have been linked to latent liability to schizophrenia, namely, smooth pursuit and antisaccade performance. The antisaccade errors in the schizotype group were primarily perseverations, a behavioral pattern often associated with frontal lobe dysfunction and observed in the performance of schizophrenic patients.

Detecting personality disorders in a nonclinical population. Application of a 2-stage procedure for case identification.

BACKGROUND: There is no epidemiology of personality disorders (PDs) comparable with that currently available for most other mental disorders. One reason for this is that an Axis II diagnosis usually requires considerable clinical sophistication and it is expensive to deploy clinicians rather than trained laypersons to examine large community samples. This study explores the feasibility of using a 2-stage method in which only subjects who were screened as positive for PD would be interviewed by clinicians. METHODS: University students were screened with a self-administered Axis II inventory and subsequently interviewed by clinicians with the use of the International Personality Disorder Examination. RESULTS: The screen detected all individuals who subsequently received a definite diagnosis on the interview, and a specificity rate of detection was 61%. The point-prevalence estimate for diagnosable PD in this nonclinical population was 11.01% (95% confidence interval, 7.57%-14.52%). CONCLUSION: If these results can be replicated in a more representative community sample, this 2-stage method might substantially reduce the number of persons who needed to be interviewed in a major epidemiological study of PDs, with little or no loss in diagnostic accuracy, while presumably lowering the cost of such an investigation.

Thought disorder, perceptual aberrations, and schizotypy.

Empirical links between schizophrenia and schizotypic psychopathology were examined. The Perceptual Aberration Scale (PerAb; L. J. Chapman, J. O. Chapman, & M. L. Raulin, 1978) was used to identify putative schizotypic individuals and a contrast group of nonschizotypic controls. The Thought Disorder Index (TDI; M. J. Coleman et al., 1993) was used to quantify and classify thought disorder in these individuals. High PerAb participants, selected for having an increased number of self-reported perceptual and body image aberrations, showed an elevation in the amount and frequency of thought disorder as well as an increased number of idiosyncratic verbalizations. This supports the hypothesis that psychometrically identified schizotypic individuals display thought disorder similar to that shown by schizophrenic patients and some of their 1st-degree relatives, suggesting that there is a relation between schizotypic psychopathology, as tapped by the PerAb scale, and clinical schizophrenia.

The dimensions of schizophrenia phenomenology. Not one or two, at least three, perhaps four.

BACKGROUND: This confirmatory investigation examined the underlying structure of schizophrenia phenomenology through examination of the fit of several prominent dimensional models to observed symptom data. METHOD: Confirmatory factor analysis was conducted on a correlation matrix of schizophrenia signs and symptoms derived from case history ratings of 192 individuals with schizophrenia who were the subjects in the major twin studies of schizophrenia. RESULTS: Schizophrenia phenomenology appears best described by four underlying factors, namely negative symptoms, premorbid social adjustment deficits, reality distortion, and disorganisation. Of interest, the premorbid deficit dimension was directly associated with negative symptoms and disorganisation, but was inversely associated with reality distortion. CONCLUSIONS: These data clearly support the multidimensionality of schizophrenia phenomenology and provide objective support for a four-factor model over other models. This four-factor model may be useful in organising existing and future data concerning the genetic, neurobiological, neurological, and psychosocial features of schizophrenia.

Individual differences in spatial working memory in relation to schizotypy.

With a delayed-response task, spatial working memory function was assessed in normal students who were selected for schizotypy. The Wisconsin Card Sorting Test was also administered. Twenty-eight undergraduate students who scored high on the Perceptual Aberration Scale (PerAb) and 23 who scored low on this scale participated in this study. High PerAb students performed less accurately compared with the low PerAb controls on the delayed-response task, and they were more than twice as likely as low PerAb students to be impaired. The groups did not differ in the number of perseverative errors or number of categories achieved on the Wisconsin Card Sorting Test, but, as predicted, high PerAb students were less able to maintain set than were the low PerAb students. Neuropsychological implications of these data are discussed.

The taxonicity of schizotypy: a replication.

P.E. Meehl's model (1962, 1990) of schizotypy and the development of schizophrenia implies that the structure of liability for schizophrenia is dichotomous, hypothesizing that a "schizogene" determines one's membership in a latent class (or taxon; P.E. Meehl & R. R. Golden, 1982). The present study sought to replicate earlier findings concerning the taxonic latent structure and general population base rate of schizotypy (M. F. Lenzenweger & L. Korfine, 1992). P.E. Meehl's (1973; P.E. Meehl & R. R. Golden, 1982) MAXCOV-HITMAX taxometric analytic procedures were applied to a subset of items from the Perceptual Aberration Scale (PAS; L. J. Chapman, J. P. Chapman, & M. L. Raulin, 1978), a prominent psychometric index of schizotypy, derived from a new randomly ascertained nonclinical university sample (N = 1,646). Consistent with the authors' previous results as well as Meehl's conjectures, the data strongly suggest that schizotypy, as assessed by the PAS, is taxonic at the latent level with a low general population taxon base rate (i.e., < .10). Moreover, individuals falling within the putative schizo-taxon underlying the PAS present greater levels of schizotypic phenomenology than nontaxon members. The taxometric analysis of the psychological trait of femininity also reveals that the MAXCOV-HITMAX procedure can detect a latent dimension, when one is hypothesized to exist, and the procedure does not appear to generate "spurious" evidence for taxonicity as a function of the psychometric format (e.g., true-false) of the data under analysis. The statistical implication of a taxonic entity occurring at a low base is discussed with respect to results obtained using the MAXCOV-HITMAX technique.

Psychometric high-risk paradigm, perceptual aberrations, and schizotypy: an update.

The psychometric high-risk strategy represents a useful methodologic adjunct to the traditional genetic high-risk research approach in the study of the etiology and development of schizophrenia. During the past 15 years, considerable research activity has focused on psychometrically identified individuals hypothesized to be en route to schizophrenia (i.e., putative schizotypes). The Perceptual Aberration Scale (PAS) has figured prominently in such prediction-oriented psychometric high-risk work. This report examines research using the PAS completed since 1987 that has established the instrument as a valid index for detecting liability for schizophrenia (or schizotypy) and as, arguably, the schizotypy index of choice for research. These results are presented and interpreted in light of Meehl's theoretical framework of schizotypy. Other measures of and assessment devices for schizotypy (schizophrenia-related liability) are identified. Of these other measures, the Chapmans' Magical Ideation Scale and the schizophrenia liability index of Moldin and colleagues are particularly well established. Methodologic suggestions for future psychometric high-risk and other work using objective measures of schizotypic psychopathology are offered. It is strongly recommended that future studies of schizotypy (or those in the planning stages, relying on psychometric detection methods use multiple psychometric indices to tap schizotypy or use a psychometric index in association with other promising biobehavioral markers of schizophrenia liability (e.g., sustained attentional deficits, eye movement dysfunction) for maximum efficiency in both location and definition of schizotypes.

Perceptual aberrations, schizotypy, and the Wisconsin Card Sorting Test.

This study examined performance on the Wisconsin Card Sorting Test (WCST) by 23 schizotypic subjects and 28 normal control subjects. Schizotypy was measured on the Perceptual Aberration Scale (PAS). Overall, schizotypic (high PAS) subjects performed more poorly than control (low PAS) subjects on the WCST; specifically, schizotypic subjects showed deficits on the failure-to-maintain-set and number-of-categories indexes. Consistent with expectations based on research with high-risk subjects, schizotypic subjects were nearly 10 times more likely than controls to be included in a subgroup of deviant WCST performers identified by a composite performance index. WCST performance was not associated with current levels of anxiety or depression. Our results provide evidence for subtle WCST performance deficits in subjects hypothesized to be at risk for psychosis--perhaps schizophrenia--and are broadly consistent with current speculation about dorsolateral prefrontal cortex functioning in schizophrenia as well as recent speculation concerning spatial working memory and schizophrenia. The heuristic potential of our results is discussed and we encourage replication of the present study. Viewed in this context, our results are hypothesis-generating and do not provide definitive confirmation of specific hypotheses.

Explorations in schizotypy and the psychometric high-risk paradigm.

This chapter has presented a brief history of clinical and research interest in schizotypic psychopathology. Specific attention was focused on the theoretical model of schizotypy proposed by Meehl (1962, 1990), and the research implications of his model were discussed. Current (i.e., post-1980) schizotypy assessment methods were highlighted for consideration by those investigators who might conceptualize future research in schizotypy. A brief overview of the psychometric high-risk approach to schizotypy detection and current research conducted by the present author was discussed. Finally, a variety of methodologic issues that should be considered in the design and execution of future schizotypy research were surveyed and specific recommendations were made.

Empirical assessment of the factorial structure of clinical symptoms in schizophrenic patients: formal thought disorder.

Male schizophrenic patients (n = 142) were examined with a clinical assessment of their language dysfunctions with the Scale for the Assessment of Thought, Language, and Communication (TLC). Confirmatory factor analyses were conducted to test the relative fit of several differential theoretical models of the factorial structure of thought disorders. The models examined were positive-negative thought disorder, a three-factor model based on the results of an earlier exploratory factor analysis, and a simpler verbal productivity-disconnection model that can be extracted from other exploratory analyses and empirical studies. The positive-negative thought disorder model failed to fit the data, while the three-factor model fit the data, but no better than the simpler verbal productivity-disconnection model.

Empirical assessment of the factorial structure of clinical symptoms in schizophrenia: negative symptoms.

The factor structure of the Scale for the Assessment of Negative Symptoms (SANS) was examined in a confirmatory factor analysis that used the LISREL procedure. Four models of negative symptom factors were tested in 130 hospitalized schizophrenic patients. A three-factor model of diminished expression, social dysfunction, and disorganization generated by the authors yielded a superior fit to the data relative to the two-factor model of Liddle (1987b) and a unifactorial severity model. A four-factor model based on the original subscale formulation of the SANS failed to fit the data.