Correlating a measure of sustained attention with a multi-dimensional measure of schizotypal traits

Schizotypal traits and their relationship to reading abilities in healthy adults

Schizotypal traits (i.e., personality characteristics that range from mild eccentricities to more pronounced schizophrenia-like perceptions, thought patterns, and behaviours) have been associated with a variety of cognitive impairments, including difficulties in language processing. Although these difficulties span several aspects of language (e.g., semantic processing, verbal fluency, visual word recognition), it is unclear whether reading abilities are also affected. Thus, the current study employed the Schizotypal Personality Questionnaire (SPQ) - Brief (Raine and Benishay, 1995) to examine how schizotypal traits impact both word-level and text-level reading skills (using a battery of standardized assessments) in a sample of healthy young adults. We found some evidence that higher schizotypal traits, specifically, increased Disorganized factor scores (reflecting aberrant thinking, communication patterns, and behaviour), were associated with reduced word-level reading abilities. However, this finding did not remain significant after correcting for multiple comparisons. Overall, our study suggests that reading may be another aspect of language affected by schizotypal traits, although additional research (with greater power) is needed to further explore and confirm this finding.

Comparing Self-Report vs. Performance Measures of Attentional Control and Efficiency

Background: The Attention Control Scale (ATTC) is a widely used self-report measure of attentional control capacities. However, research questions whether it accurately substitutes for objective attention control tasks. This study investigated ATTC's correlation with the Attention Network Test (ANT) across alerting, orienting, and executive control networks. We also used the Inverse Efficiency Score (IES) as an additional factor to check ATTC using ANT. Methods: We administered 143 participants who completed the ATTC questionnaire and ANT behavioral test assessing network efficiencies. Results: The results showed non-significant ATTC-ANT correlations across all networks. In an additional analysis, while the ATTC demonstrated factorial validity, subjective control was disconnected from actual attention regulation efficiency. A small male advantage emerged for executive control. Conclusions: Dissociations likely stem from attention complexity and method variances rather than overlap. The findings do not support the ATTC as a stand-alone proxy for performance-based measurement. Multifaceted assessments are essential for comprehensively capturing attentional control.

Schizotypy and perceptual span in a non-clinical sample: a virtual reality study

INTRODUCTION

Individuals with high schizotypy or schizophrenia exhibit difficulties in distributing their attention across space, leading to a reduction in their "perceptual span" - the extent of visual space that can be attended to at once. In this study, we aim to explore the correlation between schizotypy and perceptual span in a non-clinical sample to investigate whether perceptual span correlates with schizotypy across its range.

METHODS

Schizotypy was assessed in fifty-five participants using the Schizotypy Personality Questionnaire (SPQ; Raine, 1991). Participants were required to attend to two dynamic targets displayed in a head-mounted virtual reality display. Perceptual span was estimated as the lateral angle of separation between the two targets beyond which performance in the task dropped to threshold.

RESULTS

Participants with higher schizotypy scores performed significantly worse on the task. Of all the factors associated with schizotypy, the shared variance between Disorganisation and Cognitive/Perceptual Factors was most predictive of task performance.

CONCLUSION

The results support the hypothesis that schizotypy predicts perceptual span in non-clinical samples. Furthermore, the demonstration of a reduced perceptual span in individuals with higher trait schizotypy shows that variations in an individual's capacity to divide attention across space can be accurately captured using a virtual reality head-mounted display.

No influence of sex on the relationship between schizotypy factors and executive control across the schizophrenia spectrum

Sex differences in symptoms and executive control across schizophrenia spectrum disorders (SSD) are consistently reported. Similarly, these findings of sex differences are also observed in schizotypy, that is, schizophrenia-like features occurring in healthy individuals in the absence of a clinical diagnosis. This study aimed to examine the relationships between performance on three major domains of executive control: performance monitoring, response inhibition, and cognitive set-shifting, and schizotypy factor scores in both SSD patients and healthy controls (HCs), and whether sex moderated any relationships observed. A total of 111 (67 males and 44 females) patients with SSD and 258 (129 males and 129 females) HCs were included in this study. Schizotypal personality traits (in both SSD and HC) was assessed using the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE). Executive control performance was assessed using seven tasks. Stepwise linear regressions revealed that performance on cognitive set-shifting tasks was significantly associated with the introvertive anhedonia, cognitive disorganisation, and unusual experiences subscales of the O-LIFE. When sex was examined as a moderator, it was not a significant moderator of any of the relationships between cognitive set-shifting tasks and schizotypy factors. The results suggest that independent of sex, cognitive set-shifting ability is associated to an increased vulnerability to schizotypal personality traits, although performance monitoring and response inhibition did not.

The network structure of schizotypy in the general population

Schizotypal personality traits show similarity with schizophrenia at various levels of analysis. It is generally agreed that schizotypal personality is multidimensional; however, it is still debated whether impulsive nonconformity should be incorporated into theories and measurement of schizotypy. In addition, relatively little is known about the network structure of the four-dimensional model of schizotypal personality. To estimate the network structure of schizotypy, we used data from participants recruited from the community (N = 11,807) who completed the short version of the Oxford-Liverpool Inventory of Feelings and Experiences, a widespread self-report instrument that assesses the positive, negative, disorganised and impulsive domains of schizotypy. We performed community detection, then examined differences between communities in terms of centralities and compared the strength of edges within and between communities. We found communities that almost perfectly corresponded to the a priori-defined subscales (93% overlap, normalised mutual information = 0.74). Items in the disorganisation community had higher closeness centrality relative to items in the other communities (Cliff's Δs ranged from 0.55 to 0.83) and weights of edges within the disorganisation community were stronger as compared to the negative schizotypy and impulsive nonconformity communities (Cliff's Δs = 0.33). Our findings imply that the inclusion of impulsive nonconformity items does not dilute the classical three-factor structure of positive, negative and disorganised schizotypy. The high closeness centrality of disorganisation concurs with theories positing that cognitive slippage and associative loosening are core features of the schizophrenic phenotype.

Do schizotypy dimensions reflect the symptoms of schizophrenia?

OBJECTIVE

The personality characteristics and symptoms observed in schizophrenia are postulated to lie on a continuum, with non-clinical manifestations referred to as schizotypy. High schizotypy behaviours are argued to correspond with the three main clusters of symptoms in schizophrenia: positive, negative and cognitive/disorganised symptoms, yet there is limited empirical evidence to support this. This study aimed to investigate whether schizotypy dimensions significantly correlate with their respective schizophrenia symptomatology in the largest sample to date.

METHODS

A total of 361 adults (103 patients with schizophrenia/schizoaffective disorder and 258 healthy controls) were assessed for schizotypy using the Oxford-Liverpool Inventory of Feelings and Experiences. The MATRICS Consensus Cognitive Battery supplemented by the Stroop task and Wisconsin Card Sorting Test was administered to all participants to obtain objective measurements of cognition. Schizophrenia symptomatology was assessed using the Positive and Negative Syndrome Scale in patients only.

RESULTS

The results demonstrated significant correlations between the Oxford-Liverpool Inventory of Feelings and Experiences positive and negative subscales and their respective Positive and Negative Syndrome Scale subscales only, indicating that positive and negative schizotypy dimensions across patients and controls accurately reflect the respective schizophrenia symptomatology observed in patients. Cognitive performance did not correlate with cognitive/disorganised symptom dimensions of the Oxford-Liverpool Inventory of Feelings and Experiences or the Positive and Negative Syndrome Scale, indicating that cognitive impairment is an independent symptom dimension that requires objective cognitive testing.

CONCLUSION

Collectively, the findings provide empirical evidence for the continuum theory and support the use of schizotypy as a model for investigating schizophrenia.

The relationship between schizotypal traits and hoarding symptoms: An examination of symptom specificity and the role of perceived cognitive failures

BACKGROUND

Hoarding disorder presents significant individual and interpersonal consequences. Because hoarding has only recently been added to the DSM, relatively little is known about associated comorbidity patterns. Several researchers have postulated a relationship between hoarding and schizotypy. To date, however, no investigations have considered which specific types of schizotypal traits relate to hoarding symptoms.

METHODS

We examined the association between hoarding and schizotypal symptoms using multivariate analyses in two samples-a sample of 120 young adults and a community sample of 291 individuals recruited from Mechanical Turk's online crowdsourcing system.

RESULTS

Individuals who fell within the clinical range on the Saving Inventory Revised endorsed significantly greater levels of schizotypal symptoms compared to those with normative saving behaviors. Odd speech, magical thinking, and social anxiety were the most consistent schizotypal correlates of hoarding symptoms. Perceived cognitive dysfunction mediated the effects between odd speech and social anxiety and hoarding symptoms, suggesting that shared abnormalities in cognitive functioning may help explain the relationship between hoarding and schizotypy.

LIMITATIONS

This study examined the spectrum of schizotypy and hoarding symptoms via self-report in two nonclinical populations.

CONCLUSIONS

Findings underscore the importance of assessing schizotypal traits in patients with hoarding, and suggest future avenues of research to better understand the underlying causes explaining the overlap, as well as potential treatment implications.

Increased distractibility in schizotypy: Independent of individual differences in working memory capacity?

Individuals with schizophrenia typically show increased levels of distractibility. This has been attributed to impaired working memory capacity (WMC), since lower WMC is typically associated with higher distractibility, and schizophrenia is typically associated with impoverished WMC. Here, participants performed verbal and spatial serial recall tasks that were accompanied by to-be-ignored speech tokens. For the few trials wherein one speech token was replaced with a different token, impairment was produced to task scores (a deviation effect). Participants subsequently completed a schizotypy questionnaire and a WMC measure. Higher schizotypy scores were associated with lower WMC (as measured with operation span, OSPAN), but WMC and schizotypy scores explained unique variance in relation to the mean magnitude of the deviation effect. These results suggest that schizotypy is associated with heightened domain-general distractibility, but that this is independent of its relationship with WMC.

Schizotypal Traits are Associated with Poorer Executive Functioning in Healthy Adults

Previous research has shown mild forms of the neurocognitive impairments seen in schizophrenia among healthy individuals exhibiting high schizotypal traits. This study aimed to explore associations between schizotypy and cognitive performance in an adult community sample. Ninety-five females and 79 males completed the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), which measures four separable aspects of schizotypy: cognitive disorganization, unusual experiences, introvertive anhedonia, and impulsive non-conformity. Subsequently, participants were administered a neurocognitive battery incorporating measures of executive skills including inhibition, cognitive flexibility, reasoning, and problem solving along with measures of attention and processing speed and both verbal and spatial working memory. In line with predictions, the current study found that higher scores on the subscales of unusual experiences, cognitive disorganization, and impulsive non-conformity related to worse performance on a measure of inhibition. Additionally, as introvertive anhedonia increased, both attention and processing speed and reasoning and problem-solving performance became more impaired. In conclusion, this study extends schizotypy literature by examining the subscales of the O-LIFE, and enables inferences to be drawn in relation to cognitive impairment in schizophrenia.

Inferring about individual drug and schizotypy effects on cognitive functioning in polydrug using mephedrone users before and after clubbing

OBJECTIVE

Mephedrone has been recently made illegal in Europe, but little empirical evidence is available on its impact on human cognitive functions. We investigated acute and chronic effects of mephedrone consumption on drug-sensitive cognitive measures, while also accounting for the influence of associated additional drug use and personality features.

METHOD

Twenty-six volunteers from the general population performed tasks measuring verbal learning, verbal fluency and cognitive flexibility before and after a potential drug-taking situation (pre-clubbing and post-clubbing at dance clubs, respectively). Participants also provided information on chronic and recent drug use, schizotypal (Oxford-Liverpool Inventory of Feelings and Experiences) and depressive symptoms (Beck Depression Inventory), sleep pattern and premorbid IQ.

RESULTS

We found that (i) mephedrone users performed worse than non-users pre-clubbing and deteriorated from the pre-clubbing to the post-clubbing assessment; (ii) pre-clubbing cannabis and amphetamine (not mephedrone) use predicted relative cognitive attenuations; (iii) post-clubbing, depression scores predicted relative cognitive attenuations; and (iv) schizotypy was largely unrelated to cognitive functioning, apart from a negative relationship between cognitive disorganisation and verbal fluency.

CONCLUSION

Results suggest that polydrug use and depressive symptoms in the general population negatively affect cognition. For schizotypy, only elevated cognitive disorganisation showed potential links to a pathological cognitive profile previously reported along the psychosis dimension.

Schizotypal traits in adolescents: Links to family history of psychosis and psychological distress

Objective

Studies in the general population report that unusual subjective experiences are relatively common. Such experiences have been conceptualized either as extreme personality traits or as vulnerability markers for psychosis, and often grouped under the expression “schizotypal experiences”. This study investigates the heterogeneity of schizotypal traits using factor and latent class analysis.

Methods

One thousand and thirty-two adolescents were recruited for this study. Schizotypal experiences were assessed with the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE); psychological distress was assessed with the General Health Questionnaire (GHQ). Confirmatory Factorial Analysis (CFA) and Latent Class Analysis (LCA) were performed on the O-LIFE and on the association with the GHQ and demographic variables.

Results

CFA replicated the original 4-factor structure of the O-LIFE. Three latent classes (LC) of schizotypal features were identified: participants in LC1 (26% of the total sample) showed minimal level of item endorsement; LC2 accounted for 52% of the sample and showed overall higher item endorsement compared to LC1, especially for disorganization and positive signs of schizotypy, but not for negative affective items. LC3 (22%) showed an overall higher level of item endorsement across schizotypal dimensions, and positive association with psychological distress and family history of psychosis.

Discussion

Different latent class of schizotypal features can be empirically defined in adolescent community samples. The most extreme class is defined not only by a profile of higher positive replies to the items, but also by anhedonia, high psychological distress, and family history of psychosis. These findings can inform prevention research in schizophrenia.

The influence of tobacco consumption on the relationship between schizotypy and hemispheric asymmetry

Tobacco use is positively associated with severity of symptoms along the schizophrenia spectrum. Accordingly it could be argued that neuropsychological performance, formerly thought to be modulated by schizotypy, is actually modulated by drug use or an interaction of drug use and schizotypy. We tested whether habitual cigarette smokers as compared to non-smokers would show a neuropsychological profile similar to that observed along the schizophrenia spectrum and, if so, whether smoking status or nicotine dependence would be more significant modulators of behavior than schizotypy. Because hemispheric dominance has been found to be attenuated along the schizophrenia spectrum, 40 right-handed male students (20 non-smokers) performed lateralized left- (lexical decisions) and right- (facial decision task) hemisphere dominant tasks. All individuals completed self-report measures of schizotypy and nicotine dependence. Schizotypy predicted laterality in addition to smoking status: While positive schizotypy (Unusual Experiences) was unrelated to hemispheric performance, Cognitive Disorganization predicted reduced left hemisphere dominant language functions. These latter findings suggest that Cognitive Disorganization should be regarded separately as a potentially important mediator of thought disorganization and language processing. Additionally, increasing nicotine dependence among smokers predicted a right hemisphere shift of function in both tasks that supports the role of the right hemisphere in compulsive/impulsive behavior.

Predicting vigilance: a fresh look at an old problem

Individual differences in vigilance are ubiquitous and relevant to a variety of work environments in industrial, transportation, medical and security settings. Despite much previous work, mostly on personality traits, it remains difficult to identify vigilant operators. This paper reviews recent research that may point towards practically useful predictor variables for vigilance. Theoretical approaches to identifying predictors that accommodate the heterogeneous nature of vigilance tasks are compared. The article surveys recent empirical studies using personality measures, ability tests and scales for stress and coping as predictors of vigilance. Promising new constructs include trait scales linked to fatigue, abnormal personality and the stress state of task engagement. Implications of the data reviewed for occupational selection are discussed. Selection should be based on a multivariate assessment strategy, cognitive task analysis of the operational vigilance task and use of work sample measures to capture typical stress responses to the task. This review paper surveys recent research that may point towards practically useful predictor variables for vigilance. The article surveys recent empirical studies using personality measures, ability tests and scales for stress and coping as predictors of vigilance. Selection should be based on a multivariate assessment strategy.

Impulsivity and positive psychotic symptoms influence hostility in methamphetamine users

Methamphetamine (MA) use is associated with hostility, aggression, and positive psychotic symptoms. However, little is known of the processes or mechanisms that underlie this relationship. The present research was designed to investigate putative mediating and moderating variables between MA dependence and hostility in a sample of injecting MA users (N=237). Both positive symptoms of psychosis and higher levels of impulsivity functioned as mediators and moderators of this relationship. This pattern of findings suggests that MA use leads to greater hostility by increasing positive psychotic symptoms that contribute to a perception of the environment as a hostile and threatening place as well as by increasing impulsivity. Those who were high in positive symptoms and high in impulsivity were the most hostile. Individual differences in impulsivity and positive psychotic symptoms should be taken into account in the assessment and management of MA dependence.

Seeing non-existent events: effects of environmental conditions, schizotypal symptoms, and sub-clinical characteristics

Under conditions of perceptual ambiguity positive schizotypy and positive symptoms of schizophrenia have been associated with a bias towards reporting the presence of an event in its absence. A word detection task was employed (Experiments 1-3; N=211) to explore a number of environmental parameters, such as perceptual ambiguity (speed of stimulus presentation), and the probability of an event, in an effort to identify the empirical laws that modulate this type of bias. Overall, the obtained data suggested that high schizotypy scorers were more prone to false perceptions (false alarms) as compared to their low schizotypy counterparts, although the two groups did not differ with respect to accuracy (correct responses). High perceptual ambiguity increased false perceptions in both high and low schizotypy scorers. False perceptions increased as the probability level of the presented word increased. This tendency was especially pronounced in the high schizotypy group. False perceptions were predicted by positive schizotypy and disposition to hallucinations after controlling for trait anxiety, depression and delusional ideation.

Semantic associations, lateralized frontal function, and context maintenance in schizotypy

Symptom heterogeneity within conventional diagnostic groups is fostering a growing focus on narrower symptom profiles to identify psychological and biological mechanisms in psychopathology. Positive symptoms of schizophrenia are associated with context maintenance deficits, which in turn have been linked to frontal-lobe function. Frontal- and temporal-lobe brain dysfunction is also well documented in schizophrenia. The present study (N=36) examined how context and memory deficits are associated with subclinical symptoms in schizotypy by investigating the relationship between symptom reports, neuropsychological performance, and several facets of recognition memory. Context maintenance was probed via lures suggested by presented verbal material. Frontal brain function and positive symptom schizotypy predicted accuracy for lures, whereas posterior brain function and low positive affect predicted accuracy for distracters. This pattern of findings establishes continuity in disruption of context maintenance in clinical and subclinical populations.

Schizotypy and sustained attention: Confirming evidence from an adult community sample

Sustained attention deficits represent one of the most robust findings in the study of schizophrenia and schizotypy. However, very little is known about the nature of sustained attention performance and schizotypy in the general adult population. The present study assessed sustained attention performance in a large, normative adult community sample (N = 305) with no history of psychosis using the Continuous Performance Test-identical pairs version (CPT-IP). Associations between overall CPT-IP performance and schizotypal personality disorder features, controlling for the effects of age, sex, and educational level, revealed diminished sensitivity (d', discriminability), and increased random errors were related to increased reality distortion features. These data, drawn from a general population sample, provided support for overall sustained attention deficits as an endophenotype for schizophrenia liability.

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.

The influence of schizotypy traits on prepulse inhibition in young healthy controls

Deficits in sensorimotor gating or prepulse inhibition (PPI) have been demonstrated repeatedly in patients with schizophrenia or with schizotypal personality disorder, but not consistently in schizotypal non-psychiatric controls. The appearance of normal PPI in this group has been interpreted as reflecting a discontinuous underlying vulnerability to psychosis in high-risk groups. An alternative interpretation is that underlying vulnerability to psychosis is continuously distributed in the normal population (Claridge, 1972, 1987), and therefore that performance on information processing tasks should vary continuously with increasing levels of schizotypy in non-clinical populations. We attempted to examine further the notion of a continuous relationship between PPI and schizotypy in 44 (17 female, 27 male) healthy, non-smoking subjects controlling for menstrual phase. In this selected sample, the findings do not support a continuum model, and suggest that PPI deficits may indeed be the result of a discontinuous neurophysiological change in those with psychotic illness, rather than one continuously distributed in the normal population.