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... on associations within individual schizotypal clusters The aim of this thesis is to understand the complex relations within and between individual schizotypal clusters and identify potential neurocognitive. .. consistent findings of inverse association between schizotypy and executive functioning, several studies have failed to find an association between the two (Jahshan & Sergi, 2007; Lin, Chen, Yang,... possible associations between schizotypy with neurocognition and personality traits by correlating the individual schizotypy cluster with neurocognitive functions and measures of personality traits and
ASSOCIATION BETWEEN PERSONALITY AND NEUROCOGNITIVE DYSFUNCTIONS IN SCHIZOTYPY CLUSTERS ONG MIN YEE B. Soc. Sci. (Hons.), NUS A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF SOCIAL SCIENCES DEPARTMENT OF PSYCHOLOGY NATIONAL UNIVERSITY OF SINGAPORE 2011 i Acknowledgement I would like to express my great appreciation to my supervisor, Dr. Simon L. Collinson for his continuous guidance, dedication and expertise in the field, and his confidence in me. I would like to thank him for showing support for my work and his contribution to my growth as a psychologist. I would also like to thank him for the advices that he has given me throughout my Masters program and the opportunity that he has provided me with an attachment at the Research Department in the Institute of Mental Health (IMH). I am also deeply grateful to Prof. Chong Siow Ann and Dr. Mythily Subramaniam for the opportunity that they have provided me with. I would also like to thank the team members of Translational Clinical Research (TCR) Project 1B for assisting me with data collection, and Mr. Max Lam for his help on SPSS and data analysis. I would also like to thank Ms. Loh Poh Yee for her help on admin matters. To Melvin, I thank him for expressing his confidence in my ability and always being there for me cheering me on. His support helps me to persevere on and do better. Finally, heartfelt thanks to my family for their continuous support, encouragements, and always expressing their confidence in my ability. I thank them for their love and always providing a listening ear and going through the tough times with me. I would also like to thank my friends for their concerns and ii support. Their company and encouragements made this journey easier. Thanks everyone! iii Table of Contents Page Acknowledgements i Table of contents iii Thesis summary vi List of Tables viii List of Figures ix Chapters 1. 2. What is Schizotypy? 1 1.1. Evidence of a Continuum model 3 1.2. Schizotypy in the general population 6 1.3. Measurement of Schizotypy 8 1.4. Factor structure of Schizotypy 11 1.5. Asian studies on Schizotypy 14 Schizotypy, Neurocognition and Personality traits 16 2.1. Neurocognition 16 2.2. Non-schizotypal personality traits 20 3. Aims of Present study 23 4. Method 25 4.1. Participants 25 4.2. Clinical scales and Personality questionnaires 26 4.2.1. Structured Clinical Interview for DSM-IV Axis I 26 Disorders, Non-Patient Edition (SCID-NP) iv Page 4.3. 4.2.2. Schizotypal Personality Questionnaire (SPQ) 27 4.2.3. State-Trait Personality Inventory (SPTI) 27 Neurocognitive assessment 28 4.3.1. Brief Assessment of Cognition in Schizophrenia 29 (BACS) 4.3.2. Benton Judgment of Line Orientation Test 32 (BJLOT) 4.3.3. WAIS-III Matrix Reasoning Task 32 4.3.4. Continuous Performance Test-Identical Pair 32 (CPT-IP) 5. 4.3.5. Wisconsin Card Sorting Test-64 (WCST-64) 33 4.4. Procedure 36 4.5. Statistical Analyses 37 Results 38 5.1. Descriptive statistics 38 5.2. Cluster Analysis 38 5.2.1. Clusters for Participants 39 5.2.2. SPQ Factors 39 Associations of Clusters and SPQ Factors with 41 5.3. Neurocognition and STPI 5.3.1. Schizotypal Clusters 5.3.1.1. Neurocognition 41 42 v Page 5.3.1.2. STPI 5.3.2. New SPQ Factors 6. 43 46 5.3.2.1. Neurocognition 46 5.3.2.2. STPI 50 Discussion 54 6.1. Schizotypal clusters and SPQ factors 55 6.2. Associations of schizotypal clusters with 57 Neurocognition and STPI 6.3. 6.2.1. Neurocognition 57 6.2.2. STPI 58 Associations of SPQ features with Neurocognition 60 and STPI 6.3.1. Neurocognition 60 6.3.2. STPI 66 6.4. Implications of present study 69 6.5. Study limitations and future directions 71 6.6. Conclusions 73 7. References 74 8. Appendices 94 8.1. Appendix A 94 8.2. Appendix B 95 vi Thesis summary Studies have shown that individuals with schizotypy share similar neurocognitive impairments and certain personality traits as those found in clinically diagnosed schizophrenia patient. As a multidimensional construct, schizotypy consists of multiple personality features including cognitions, beliefs and behaviors. Similar or co-occurring features are grouped together forming a schizotypal cluster. To date, only a few studies have focused on associations within individual schizotypal clusters. The aim of this thesis is to understand the complex relations within and between individual schizotypal clusters and identify potential neurocognitive endophenotypes and non-schizotypal personality traits that may indicate enhanced risk for schizophrenia. English speaking Singaporean Chinese (N = 198) were assessed by the Schizotypal Personality Questionnaire (SPQ), cognitive functions through the Brief Assessment of Cognition in Schizophrenia (BACS), and non-schizotypal personality traits by the State-Trait Personality Inventory (STPI). A two-way clustering analysis was performed for generating schizotypy clusters and SPQ factors. Three schizotypy clusters (Low, High Positive, and High Positive/Negative) and three new SPQ factors (Referential Thinking, Anxiety, and Social Interaction Deficit) were found. In relations to positive schizotypal features, individuals scoring high on SPQ performed poorer on almost all neurocognitive measures especially on working memory, attention, non-verbal abstract problem solving and executive functioning. No correlation was found with negative schizotypy. In addition, individuals with high schizotypal traits were found to vii report higher levels of negative emotions such as anger, anxiety and depression. State anxiety best predicted high schizotypal individuals under the Referential Thinking factor, trait curiosity was found to negatively predict high schizotypal individuals under the Anxiety factor, and trait anger predicted high schizotypal individuals under the Social Interaction Deficit factor. These results showed that different profiles of schizotypal features contribute to the heterogeneity of neurocognitive functioning, emotional states and personality traits. Along with present findings and future genetic research and more formalized measures, future studies may possibly create a form of classification system useful in simplifying the complex nature of schizotypy. viii List of Tables Page 1. Self-report scales for measuring schizotypy 10 2. BACS tests in the MATRICS neurocognitive domains 31 3. Measures used in present study 35 4. Demographic data based on schizotypy clusters: mean (SD) 41 5. Kruskal-Wallis tests showing differences between clusters on STPI subscale 44 6. Logistic regression analysis of high positive/negative schizotypy cluster with STPI 45 7. Pearson‟s correlations between new SPQ factors and neurocognitive tests 47 8. Pearson‟s correlations between new SPQ factors and neurocognitive tests within individual schizotypal cluster 49 9. Regression coefficients between STPI and new SPQ factors 51 10. Regression coefficients between STPI and new SPQ factors within individual schizotypal cluster 52 ix List of Figures Page 1. Figure showing a Continuum model 3 2. Mean values of each STPI subscales for the schizotypy clusters 45 3. Mean values of each STPI subscales for low and collapsed high schizotypy clusters 46 1 1. What is Schizotypy? Schizotypal personality, often referred to as schizotypy, is a multidimensional construct which refers to a collection of biologically determined personality factors that are reflected in cognitive style and perceptual experiences and manifest as sub-clinical levels of psychotic-like behaviors in psychologically healthy individuals (Claridge, 1985). Within the general population, the incidence of positive psychotic experiences such as thought interference, persecution and auditory hallucination has been found to be 100 times greater than the incidence of psychotic disorders such as schizophrenia (Hanssen, Bak, Bijl, Vollebergh, & van Os, 2005). Consistent findings indicate that a substantial proportion of individuals experience hallucinations or delusional phenomena of some kind at some point of their lives (Barrett & Etheridge, 1992; Eaton, Romanoski, Anthony, & Nestadt, 1991; Posey & Losch, 1983; cited in van Os, 2003). Approximately 28% of individuals in the general population endorsed psychosis-screening questions as measured by the US National Comorbidity Survey (Johns & van Os, 2001). However of the 28%, only 0.7% falls into the broadly defined psychosis upon clinical diagnosis (Kendler, Gallagher, Abelson, & Kessler, 1996; cited in Johns & van Os, 2001). Whilst overt experiences may not persist and continue to manifest sub-clinically, in some cases schizotypy may be a precursor to the development of a clinical syndrome. Schizotypy may also be viewed as the premorbid stage of clinical disorders such as schizophrenia and other schizophrenia spectrum disorders including schizotypal personality disorder (SPD), schizoid personality disorder, 2 and schizoaffective disorder. Schizophrenia is a mental disorder characterized by disturbances in thought, emotion, and behaviors which affect one‟s social, cognitive and emotional functioning (Kring, Davison, Neale, & Johnson, 2007). It is estimated to affect 1% of the population (Johns & van Os, 2001). In contrast, SPD is a disorder viewed as the attenuated form, or prodromal stage of schizophrenia (Raine, 2006). The criteria for SPD were first derived from an examination of clinical features that characterized borderline schizophrenia patients who were mainly the first- and second-degree relatives of schizophrenia adoptees in the Danish Adoptee Study (Kety, Rosenthal, Wender, & Schulsinger, 1968; cited in Squires-Wheeler, Skodol, Friedman, & Erlenmeyer-Kimling, 1988). These criteria were put forth in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III; American Psychiatric Association, 1980), which focused on SPD rather than schizotypal personality per se. Prevalence rate of SPD has been estimated at around 2% to 3%, and it has been found to have similar cognitive and neurobiological deficits as that of individuals with schizophrenia (Sperry, 2003). 3 Figure 1. Figure showing a Continuum model. A continuous relationship between level of psychotic symptoms and need for care. Point A represents schizotypy in the general population, point B represents schizophrenia spectrum disorders such as SPD, and point C represents schizophrenia. 1. Johns & van Os, 2001. Taken together, a continuum is formed (shown in figure 1) ranging from relative psychological health to various degrees of subclinical deviance to schizophrenia spectrum personality disorders and to full-blown schizophrenia (Raballo & Parnas, 2010). Schizotypy at best may be viewed as a cluster of personality traits that are found to be varied among healthy individuals in the nonclinical general population. 1.1. Evidence of a Continuum model Theoretical models have been developed over the years to understand the continuity from sub-clinical behaviors as found in schizotypy to clinically diagnosable psychopathology within schizophrenia spectrum disorders. Three theoretical models of schizotypal personality have been developed: the quasi- 4 dimensional model (Meehl, 1962), the totally dimensional model (Eysenck, 1947), and the fully dimensional model (Claridge, 1997). Meehl‟s (1962) quasi-dimensional model represents a categorical approach to schizophrenic etiology by delineating a clear distinction between signs of health and those of disorder. According to this model, schizotypal personality traits are likely to have biological origins, such as developmental neural defects that may predispose to schizophrenia. This concept is known as schizotaxia (Meehl, 1990). The quasi-dimensional model views schizotypy as a personality organization resulting from the interaction of an inherited schizotaxia brain that combined with environmental factors ultimately lead to the outward expression of vulnerability similar to, but less of schizophrenia (Green, Boyle, & Raine, 2008). This model focuses on abnormal brain states and schizophrenia-like behaviors; thus continuity of functions is placed in the abnormal sphere rather than a continuation from normal to abnormal. Hence the quasi-dimensional model does not illustrate continuity of psychotic experiences from the general population to clinically diagnosed illness. On the other hand, the totally and fully dimensional models propose continuity of schizotypal personality traits from the general population to clinical disorders. Eysenck‟s (1947) totally dimensional model does not make any distinction between enduring psychotic experiences and signs of abnormality. While the fully dimensional model by Claridge (1997) proposes a distinct boundary along the schizotypal-schizophrenia continuum, where discontinuity of functions denotes the disorder (Green et al., 2008) and variations in perceptual 5 experiences in the general population are deemed as normal (Claridge & Beech, 1995; cited in Green et al., 2008). This model thus proposes a continuum of personality traits and dispositions that range from healthy functioning to florid psychosis as found in schizophrenia and SPD. According to the fully dimensional model, symptoms and dysfunctions observed in schizophrenia may be regarded as exaggerated manifestations of traits that can be found in healthy individuals (Avons, Nunn, Chan, & Armstrong, 2003). Schizotypal traits may represent both adaptive variations in personality and maladaptive psychological functioning. In agreement with the fully dimensional model, Rose and Barker (1978; cited in van Os, 2003) proposed that disease at the level of the general population normally exists as a continuum of severity rather than as an all-or-none phenomenon. Diathesis-stress models support this view. Diathesis, or vulnerability, is the notion of predisposition that confers greater than average liability to develop an illness, in this case schizophrenia (Parnas, 1999). Such liability is assumed to be genetic or biological dysfunction. Besides genetic vulnerability, the presence of other personality traits, absence or presence of protective factors, psychosocial factors and external factors such as adverse life experiences may also play a part in the transformation (Green et al., 2008). Diathesis-stress models thus claim that only a certain fraction of vulnerable individuals, when additionally exposed to environmental stress factors, develop overt schizophrenia psychosis, while the remaining either exhibit subclinical manifestations or asymptomatic (Parnas, 1999). 6 Evidence for a continuum of severity in schizophrenia spectrum disorders is supported by reported differences in cognition, behavior and the likelihood conversion to schizophrenia. For instance, studies of cognitive dysfunction in schizophrenia-spectrum participants have shown that people with SPD performed intermediate to healthy controls and schizophrenia patients on measures of attention, abstract reasoning, cognitive inhibition, memory and general intellectual functioning (Cadenhead, Perry, Shafer, & Braff, 1999). Several authors have also reported that anxiety and depression were strongly associated with the positive factor of schizotypy, similar to that of schizophrenia studies‟ findings (Emsley, Oosthuizen, Joubert, Roberts, & Stein, 1999; Lewanowski et al., 2006). In another study, 7.6% of children at age 10 with schizotypal-like diagnosis were diagnosed with schizophrenia by age 27 (Wolff, Townshend, McGuire, & Weeks, 1991). Based on these findings, a continuum of severity can be found ranging from schizotypy in the general population to schizophrenia spectrum disorders, which lends support to Claridge‟s fully dimensional model. Hence, schizotypy and SPD can be viewed as qualitatively similar to, but quantitatively less severe than schizophrenia (Linney et al., 2003). 1.2. Schizotypy in the general population The continuum model, as reviewed, justifies the use of psychometrically defined schizotypal individuals from the general population that may provide potential insights into schizophrenia and other schizophrenia spectrum disorders. 7 Psychometrically defined schizotypal individuals are healthy individuals from the general population who score high on measures of schizotypal personality. This approach has advantages over the investigation of schizophrenia patients as clinical studies are often confounded by factors such as long-term hospitalization, effects caused by psychotropic medication and general intellectual impairments (Avons et al., 2003; Cadenhead et al., 1999). Studies of schizotypy avoid these problems that are inherent in studies involving schizophrenia patients. Thus, schizotypy studies provide the opportunity to investigate biological and cognitive markers of vulnerability for schizophrenia. In addition, the nature of different populations from which schizotypal subjects are derived may also significantly impact the findings. For instance, most of the current literature involved student population due to ease of recruitment. However student population may prevent generalizability of findings, as they tend to be high functioning and more cognitively advantaged than the normal population (Gooding, Matts, & Rollman, 2006; Kendler et al., 1991). Furthermore, student participants are similar in characteristics, stage of life and stress, and therefore lack diversity. Conversely, variations can be observed in the general population and findings are more generalizable as compared to findings from student samples. Hence research samples taken from the non-clinical general population are much superior to student samples. A final advantage of using psychometrically defined schizotypes is the ability to obtain information that are useful for early detection of „high-risk‟ individuals developing psychosis and therefore allowing preventive measures to 8 be taken (Green et al., 2008). Schizotypy thus serves as a basis for investigating predispositions to schizophrenia and schizophrenia spectrum disorders (Avons et al., 2003). 1.3. Measurement of Schizotypy There are two ways of assessing schizotypy in the general population: 1) the familial approach, which involves the study of aberrant but non-psychotic biological relatives of schizophrenia patients (Claridge, 1985; Kendler, 1985), and 2) the clinical approach, which involves psychometrically defined individuals high on schizotypal traits regardless of family history of illness (Kendler, 1985). The familial approach observes possible schizotypal characteristics found in relatives of patients due to potential existing heritability and relatives of these patients may display attenuated forms of symptoms. On the other hand, the clinical approach targets individuals who score high on self-report scales that measure schizotypal personality traits regardless of whether they have an existing heritability or not. These two perspectives provide different ways to investigate the complexity of symptoms in schizotypal personality. Schizotypal personality traits are usually measured through self-report scales where participants were asked to answer a series of questions pertaining to previous psychotic and psychosis like experiences. The content and style of psychometric measures of schizotypal personality traits vary according to investigators‟ aims and theoretical standing (Green et al., 2008). Presently, several different scales are used widely; some focus on measuring attenuated 9 forms of specific schizophrenia symptoms, such as perceptual aberration (Chapman, Chapman, & Raulin, 1978), magical ideation (Eckblad & Chapman, 1983) and the like. While other psychometric scales, such as the Schizotypal Personality Questionnaire (SPQ; Raine, 1991) and the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE; Mason, Claridge, & Jackson, 1995), focus on tapping the general schizotypy construct based upon empirically observed factor structure of schizotypy. A list of self-report scales for measuring schizotypal personality traits may be found in Table 1. Although self-report scales are widely used, they are not the best form of measurement. For instance, participants are asked to answer either yes or no on items representative of schizotypy features, and this does not effectively detect features such as odd speech and behaviors which are better identified through interviews (Kremen, Faraone, Toomey, Seidman, & Tsuang, 1998). In particular, participants may not report truthfully due to the tendency to respond in a socially desirable manner, and thus under-reporting the presence of psychotic-like experiences. Furthermore, different schizotypy questionnaires only measure one or a few of the nine features of schizotypal traits (Raine, 1991), hence undermining the accuracy of results which depends on the input of features that were measured. Nonetheless, despite these limitations, self-report scales are still widely used in schizotypy studies due to ease of administration, low cost and less time consumed. 10 Table 1 Self-report scales for measuring schizotypy1 Schizotypy scales Schizoidia References Golden & Meehl (1979) Comments Seven-item scale derived from MMPI Chapman et al. scales Perceptual Aberration Scale (PAS) Chapman et al. (1978) Tendency to perceptual distortion Physical and Social Anhedonia Scales Chapman, Chapman, & Raulin (1976) Loss of pleasure from sensory and social sources Revised Social Anhedonia Scale Eckblad, Chapman, Chapman, Mishlove (1982) Schizoid indifference Magical Ideation Scale (MIS) Eckblad & Chapman (1983) Superstitions and other magical beliefs Social Fear Raulin & Wee (1984) Intense Ambivalence Raulin (1984) Cognitive Slippage Miers & Raulin (1985) Hypomanic Personality Scale (HoP) Eckblad & Chapman (1986) Impulsive and manic behavior Schizotypal Personality Scale (STA) Claridge & Broks (1984) Modeled on DSM-III criteria for schizotypal disorder Launay-Slade Hallucination Scale Launay & Slade (1981) Measure of predisposition to hallucinate Peters et al. Delusions Inventory (PDI) Peters, Joseph, & Garety (1999) Measure of predisposition to delusions Paranoia/Suspiciousness Questionnaire Rawlings & Freeman (1996) Schizophrenism Scale Nielsen & Pettersen (1976) Attentional difficulties and social anxiety Rust Inventory of Schizoid Cognitions (RISC) Rust (1987, 1988) Taps on positive aspects of schizotypy Psychoticism Scale Eysenck & Eysenck (1975) Eysenck, Eysenck, & Barrett (1985) Part of four-scale Eysenck Personality Questionnaire Schizophrenism and Anhedonia scales Venables, Wilkins, Mitchell, & Raine (1990) Measures of both positive and negative aspects of schizotypy 11 Schizotypy scales References Comments Schizotypal Personality Questionnaire (SPQ) Raine (1991) Modeled on DSM-III-R criteria for schizotypal personality disorder Oxford-Liverpool Inventory of Feelings and Experiences (OLIFE) Mason et al. (1995) Combined Schizotypal Traits Claridge & Beech (1996) Questionnaire (CSTQ) 1. Part of the table from Mason, Claridge, & Williams (1997) 1.4. Factor structure of Schizotypy Having multiple features, organization of similar features into distinct factors is paramount to understanding schizotypy. This is because the principal profile or schizotypal trait dimension that characterizes an individual may affect one‟s cognitive performances and behaviors (Barrantes-Vidal et al., 2001). This heterogeneity can be simplified through factor analysis. Factor analysis is a correlational method that generally „forces‟ psychometrically identified schizotypes into one of the schizotypal dimensions without taking into considerations that an individual may score high on more than one dimension at the same time (Walker & Lewine, 1988; cited in Suhr & Spitznagel, 2001b). Unfortunately, most studies still use factor analysis as it categorizes individuals „cleanly‟ into one of the schizotypal dimensions. In the early schizotypy research, a simple two-factor model was first conceptualized (Allen, Chapman, Chapman, Vuchetich, & Frost, 1987; Bentall, Claridge, & Slade, 1989) with features either classified as “positive” or “negative”. Positive features are heightened levels of normal functioning, such as 12 visual and auditory hallucinations, delusions, unusual perceptual experiences and magical thinking. While features of reduced levels as compared to normal functioning are classified as negative, such as constricted affect and social anhedonia, due to the lack of emotional reactivity and pleasure in social activities. Beyond the simple two-factor model, a three-factor model that correlates well with clinically assessed schizophrenia is more consistently found (Chen, Hsiao, & Lin, 1997; Raine, 2006; Raine et al., 1994; Vollema & van den Bosch, 1995). The additional factor is formed by the splitting of the positive features into two separate factors as defined by delusions and hallucinations, and bizarre thoughts and behaviors respectively. In the study by Raine and colleagues (1994), five competing models on the structure of schizotypy were scrutinized. A confirmatory factor analysis was used to examine the factorial structure of the SPQ and to assess the fit of each model to the data collected from the population. A consistent three-factor model was found in both undergraduates and adults from the community. The nine features of schizotypy as measured by SPQ can be separated into three factors namely, positive schizotypy or cognitive-perceptual deficits (i.e. ideas of reference, magical thinking, unusual perceptual experiences and suspiciousness), negative schizotypy or interpersonal deficits (i.e. excessive social anxiety, no close friends, constricted affect and suspiciousness), and disorganized features (i.e. odd behavior and odd speech). Though multiple features of schizotypy were found best categorized into three factors, recent confirmatory factor analyses have otherwise suggested possible structures which include latent factors beyond the basic three. In a study 13 by Compton, Goulding, Bakeman, & McClure-Tone (2009), a four-factor model was found as a better fit compared to the traditional three-factor model. The model included: 1) a cognitive-perceptual factor consisting of only magical thinking and unusual perceptual experiences, 2) a negative factor inclusive of suspiciousness, excessive social anxiety, no close friends and constricted affect, 3) a disorganized factor which included odd speech and odd behavior, and 4) a “paranoid” factor that included ideas of reference, suspiciousness and excessive social anxiety. Discrepancies in findings were due to the type of models that were tested in the different studies. For instance, Raine et al.‟s study (1994) did not include a four-factor model for assessment, while the study by Compton et al. (2009) did. Hence the exclusion of models affected the results even though similar statistical technique was used. In recent years, several reports have emerged using cluster analysis, a statistical technique that measures the interrelationship between patients‟ responses to measures of symptoms, as compared to factor analysis which measures the interrelationship between measures of symptoms (Aldenderfer & Blashfield, 1984; cited in Suhr & Spitznagel, 2001a). Cluster analysis recognizes that an individual may not „cleanly‟ fit into a specific dimension (i.e. positive, negative, or disorganized). In a study by Williams (1994), healthy students were classified into four clusters: 1) low on schizotypy, 2) high on positive schizotypy, 3) high on negative schizotypy, and 4) high on both positive and negative schizotypy. Other studies have reported similar clusters (Loughland & Williams, 1997; Suhr & Spitznagel, 2001a). In general, it is more appropriate to use cluster 14 analysis in grouping people of similar characteristics together, in contrast to factor analysis which only serves to group variables into coherent factors. Despite continuing disagreement on the factor structure of schizotypal personality, the standard cognitive-perceptual, interpersonal, and disorganized subscales are consistently supported. Similarities between the three-factor structure of schizotypal personality and the positive, negative and disorganized symptoms of schizophrenia further support the continuum model from schizotypy to schizophrenia on the biological and cognitive processes (Badcock & Dragović, 2006). 1.5. Asian studies on Schizotypy To date, most studies of schizotypy had been carried out in Western population. However there were a few studies which examined schizotypy in the Asian culture. Given unique group characteristics such as cultural and ethnic differences, schizotypy may or may not be affected differently. In a study by Guo and colleagues (2011), a gender effect in schizotypy was investigated in a Chinese population. In line with previous Western studies, gender differences were found related to negative schizotypal personality traits, namely no close friends and constricted affect. In contrast, no gender difference was found in positive schizotypal personality traits. The lack of gender difference in positive schizotypal features may be a by-product of inaccurate self-reports due to Chinese culture being less tolerant towards abnormal experiences such as hallucination and delusions (Chen et al., 1997). Cultural differences, may also 15 affect the factor structure of schizotypy. For instance, Asians have been known to exhibit more positive features due to Chinese mystical beliefs in astrology, spiritualism and reincarnation (Chen et al., 1997). This could translate into a factor structure that emphasizes positive dimensions. Despite this cross-cultural difference, Chen et al.‟s (1997) study still replicated the three-factor model in Taiwanese adults and adolescents. Hence the three-factor schizotypy may indeed apply across cultures. In yet another study by Seah and Ang (2008), junior high school students in Singapore revealed that reactively aggressive adolescents were likely to display schizotypal traits even after controlling for covariates such as age, gender and proactive aggression. This is similar to Western studies‟ findings on aggression and schizotypy (refer to Section 2.2.). In sum, more studies need to be carried out in order to understand the impact of cross-cultural differences on schizotypy. It is important for future Asian schizotypy research to substantiate current findings and determine the generalizability of schizotypy across cultures. 16 2. Schizotypy, Neurocognition and Personality traits 2.1. Neurocognition Studies of schizotypy have reported that psychometrically defined individuals are likely to demonstrate cognitive impairments similar to those found in schizophrenia patients. In line with the continuum model, these similarities may underline shared vulnerabilities between schizotypy and schizophrenia. Neurocognitive impairments may offer the potential to investigate genetic and neurobiological diatheses as these impairments represent phenotypic expression of the illness, which potentially represent simpler clues to the genetic structure of a disorder (Gottesman & Gould, 2003). Neurocognitive functions are thus forms of endophenotypes. Endophenotypes are measurable components along the pathway between diseases and distal genotype, and is important in the study of complex neuropsychiatric diseases. They may be neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, or neuropsychological in nature (Gottesman & Gould, 2003). To be useful, an endophenotype must fulfill the criteria of being associated with the illness, being state independent, heritable, and can be found in unaffected relatives at a higher rate than in the general population in addition to at least partially known neurobiological substrate (Wang et al., 2008). In this section, the focus will be on the association between cognitive endophenotypes and schizotypy. Cognitive dysfunction has been identified as one of the central abnormalities found in schizophrenia patients, likewise in other schizophrenia spectrum population such as clinically defined SPD patients, relatives of 17 schizophrenia patients and psychosis-prone individuals (Cadenhead et al., 1999; Wang et al., 2008). Moreover, studies of schizotypy have also extensively researched neurocognitive endophenotypes and demonstrated impairments similar to those found in schizophrenia patients. Thus research dealing with cognitive dysfunction further supports the continuation from normality to clinically diagnosed illness and may prove useful in understanding underlying diatheses of schizophrenia. Few studies have assessed schizotypy and its association with a wide range of cognitive functions (e.g. Barrantes-Vidal et al., 2002; Dinn, Harris, Aycicegi, Greene, & Andover, 2002; Noguchi, Hori, & Kunugi, 2008; Ruiz, Barrantes-Vidal, Guitart, & Fañanás, 2008), while many others only assess association between schizotypy to specific cognitive functions (e.g. Chen et al., 1997; Gooding, Kwapil, & Tallent, 1999; Gooding et al., 2006; Lenzenweger, Cornblatt, & Putnick, 1991). In the study by Noguchi and colleagues (2008), psychometrically defined schizotypal individuals from the general population were evaluated on a variety of cognitive functions. Results showed a negative correlation between SPQ positive subscales, and verbal IQ. In another study on verbal fluency, Tsakanikos and Claridge (2005) found a positive correlation between positive schizotypy and verbal fluency. In contrast a negative correlation was found between negative schizotypy and verbal fluency. Association of poor verbal fluency with negative schizotypy, such as flat affect, anhedonia, and impoverished speech, may reflect executive functioning impairment. Conversely, association of increased verbal fluency with positive schizotypy may be due to an 18 increase in automatic spreading activation in the semantic networks (Tsakanikos & Claridge, 2005). This was observed through increased reports of hallucinationlike experiences, delusional ideation and perceptual aberrations (Tsakanikos & Claridge, 2005). Executive functioning is also widely researched as a potential cognitive endophenotype and proxy variable to frontal lobe dysfunction. In a study of college students (Gooding et al., 1999), a high schizotypal traits group displayed deficits in aspects of executive functioning, namely inhibitory control and working memory as measured by the Wisconsin Card Sorting Test (WCST; Heaton, Chelune, Talley, Kay, & Curtiss, 1993). Studies of high positive and negative schizotypal groups also reported poorer performance on the WCST especially on working memory with more perseverative errors and increased number of trials needed to complete the first category (Barrantes-Vidal et al., 2002; Raine, Sheard, Reynolds, & Lencz, 1992; Tallent & Gooding, 1999). Taken together, these findings support the hypothesis of executive functioning deficits preceding the onset of schizophrenia and schizophrenia spectrum disorders. Despite consistent findings of inverse association between schizotypy and executive functioning, several studies have failed to find an association between the two (Jahshan & Sergi, 2007; Lin, Chen, Yang, Hsiao, & Tien, 2000; cited in Avons et al., 2003). It has been proposed that executive function may be broken down into three components: set or task shifting, memory updating, and inhibition of pre-potent responses (Miyake et al., 2000; cited in Avons et al., 2003). The WCST only taps into the set shifting component. Inconsistencies in findings may 19 be due to other tasks, such as the Trail Making Test or The Tower of Hanoi Test, tapping into a different component of executive function such as memory updating. Following the schizophrenia-spectrum model, evidence of sustained attention dysfunction has been reported in both schizophrenia patients and children at risk of schizophrenia (Lenzenweger et al., 1991). Thus psychometrically defined schizotypal individuals may also display attentional deficits. For example, in a study with non-clinical university population, students with high schizotypal traits performed significantly poorer on the Continuous Performance Test-Identical Pair (CPT-IP), as measured by poorer discriminability, d’, and lower hit rate (Lenzenweger et al., 1991). Furthermore, the poorer sustained-attention performance was not related to any mental state factors including anxiety and depression. Similar results were also achieved with a different population sample such as with Taiwanese adults and adolescents (Chen et al., 1997). However there are inconsistencies among studies of sustained attention. For instance, Chen et al. (1997) found interpersonal deficits of schizotypy to be related to poorer attention, whereas Noguchi et al. (2008) showed that schizotypy did not associate with poorer attention. Even if an association was found, there were also disagreements as to which schizotypal dimension is truly responsible for attentional deficits. For instance, attentional deficits have been associated with either positive (Lenzenweger et al., 1991), negative (Chen et al., 1997), or both schizotypal dimensions (Gooding et al., 2006). This discrepancy could be due to 20 the type of CPT used. Some CPT tasks require a response to a target stimulus such as the CPT-IP, whereas others require an inhibition of response when the target appears (Suhr & Spitznagel, 2001b). Despite inconclusive evidence, the presence of cognitive deficits in psychometrically defined schizotypal individuals from the general population offers the potential for schizophrenia phenotyping. Thus studying the associations between arrays of neurocognitive endophenotypes within high schizotypal individuals may prove useful. Furthermore, early identification of high risk individuals and implementation of protective measures are made possible with such studies. 2.2. Non-schizotypal personality traits According to the diathesis-stress model, the notion that behavioral expression of the biological vulnerability of schizophrenia may be influenced by exposure to stress in life (Rosenthal, 1970; cited in Walker & Diforio, 1997). Predispositions such as non-schizotypal personality traits, psychosocial factors and external factors such as adverse life experiences thus play a part in the continuation to schizophrenia (Green et al., 2008). For instance, the presence or absence of certain personality traits may predispose one to experience psychotic symptoms or may instead be a protective. Ross and colleagues (2002) asked university students to complete positive and negative scales of schizotypy along with the Revised NEO Personality Inventory (NEO-PI-R; Costa & McCrae, 1992) which assesses the so called Big 21 Five personality traits of Neuroticism (N), Extraversion (E), Openness (O), Agreeableness (A), and Conscientiousness (C). In general, schizotypal personality was found to be negatively related to E and A, while positively related to O and N. Results showed that negative symptoms were positively related to N, while negatively related to E, O and A. On the other hand, positive symptoms were positively related to N and O, while negatively related to A (Ross et al., 2002). People with high level of N may experience more depression and self-focused anxiety which could then lead to heightened emotional arousal (Claridge, 1985). Theoretically, heightened arousal may in turn lead to positive symptoms such as thought disorders, suspiciousness, hallucination and delusions. On the other hand, low level of A may imply the propensity to distrust others which could translate into interpersonal deficits, suspiciousness and even persecutory delusions. Furthermore, E being negatively related to schizotypy is also consistent with the aloof and detached characteristics of interpersonal deficits (Ross et al., 2002). Besides the Big Five, other non-schizotypal personality traits have also been examined. For instance, aggressiveness was found to be associated with cognitive-perceptual deficits due to an increase in perception of environmental cues as hostile and threatening (Lapworth et al., 2009; McNiel, 1994). This is because clinically anxious individuals may have attentional bias towards threatening or hostile cues, as a result higher levels of aggression were expressed (Seah & Ang, 2008). This reactive aggression may then contribute to the formation of characteristics that are suggestive of schizotypal personality such as unusual perceptual experiences, ideas of reference and paranoid ideation (Raine et 22 al., 2006). A study conducted with college-age cannabis users found that participants‟ SPQ scores were positively related with their levels of reactive aggression and not due to their cannabis usage (Schaub, Boesch, & Stohler, 2006). Though the above studies provided important insights into the impact of personality traits on schizotypy, present findings are still conflicting and insubstantial. For instance, Lewandowski et al. (2006) found anxiety and depression to be more related to positive than negative schizotypy, yet another study found positive schizotypy associated with anxiety and depression while negative schizotypy was only associated with depression (Mohanty et al., 2008). On the other hand, only negative schizotypy was found associated with high levels of anxiety (Braunstein-Bercovitz, 2000). To the best of our knowledge, no study has yet found an association between personality traits and disorganized features of schizotypy. In conclusion, non-schizotypal personality traits are also important in developing an understanding of the continuation of schizotypy to schizophrenia and other schizophrenia-spectrum disorders. To date, research on this aspect has been minimal, thus the integration of personality traits can help better understand its impact on schizotypy and schizophrenia. 23 3. Aims of Present study Based on the above literature review, several issues in the literature are apparent; first, studies conflict with regards to the factor structure of schizotypy due to methodological differences and impact of different population (i.e. Asians versus Westerners); second, most studies only investigate schizotypy as a whole construct without in-depth examination of individual schizotypy dimensions and their association with specific neurocognitive deficits and personality traits. Thirdly, there is also a lack of knowledge on non-schizotypal personality traits affecting schizotypy. Lastly, though several cognitive impairments were found present in both schizotypy and schizophrenia, evidence showing specific cognitive functions as potential endophenotypes is still far from being conclusive. The specific aims of this study are therefore, firstly, to explore the presence of different schizotypy clusters and determine the factor structure of schizotypy in a non-clinical Asian population by means of cluster analysis. Secondly, to identify possible associations between schizotypy with neurocognition and personality traits by correlating the individual schizotypy cluster with neurocognitive functions and measures of personality traits and emotional states. Thirdly, this study also aims to determine potential endophenotypes that are shared between schizotypy and schizophrenia, so as to uncover possible etiological factors of schizophrenia and other schizophrenia spectrum disorders via the investigation of schizotypy. Hence, the present study will investigate schizotypy in an Asian population, specifically in healthy English speaking Singaporean Chinese. Due to 24 possible cultural differences in the expression of schizophreniform behaviors, the factor structure of schizotypy in this Asian population will first be determined. According to limited literature relating to cluster analysis (Loughland & Williams, 1997; Suhr & Spitznagel, 2001a, Williams, 1994), four different schizotypal clusters may be hypothesized. The clusters are namely; low schizotypy, high positive schizotypy, high negative schizotypy, and high positive and negative schizotypy. Secondly, to attain in-depth understanding on how different profiles of schizotypy may affect functioning and behaviors, an array of neurocognitive tasks and measures of non-schizotypal personality traits are included in this study. The discovery of associations between schizotypy and neurocognition and personality traits may help resolve current conflicting findings. We expect participants scoring high on several schizotypy dimensions to perform worse on the tasks and also to feel more anxious and depressed. Thirdly, we also expect deficits in executive functioning, sustained attention and memory to be apparent in the high schizotypy cluster. It is important to note that this study is exploratory in nature. 25 4. Method 4.1. Participants This study was carried out at the Institute of Mental Health (IMH), the only mental health treatment facility in Singapore. One hundred and ninety-eight healthy English speaking Singaporean Chinese (113 males and 85 females) were sampled from the general population. This sample is based on a random selection of available data from a larger study aimed at elucidating the genetic architecture of neurocognitive endophenotypes in schizophrenia. The study was approved by the relevant institutional ethics and review board – the National Healthcare Group Domain-Specific Review Boards (DSRB). For the larger study, both healthy controls from the general population and patients with schizophrenia were recruited. As for the present study, only data from healthy participants were used for analysis. Healthy participants were screened and recruited based on the following criteria: 1) Age 21-55 with no history of DSM psychotic disorder based on an initial screening form and diagnostic interview using Structured Clinical Interview for DSM-IV Axis I Disorders, Non-Patient Edition (SCID-NP; First, Spitzer, Gibbon, & Williams, 2007). 2) Chinese ethnicity 3) No clinically significant neurological disease or head injury 4) Ability to understand spoken English sufficiently to comprehend testing procedures 5) Education level above primary level education 26 6) No significant history of alcohol or drug abuse that would affect neuropsychological test performance 7) No color blindness 8) No first degree relative with Schizophrenia who have participated in this study Participants were recruited from the general population through advertisements placed in local newspapers. Upon completion of the whole assessment, they were reimbursed S$70 as inconvenience fees. Written informed consent was obtained from all participants after explanation of the study procedure. 4.2. Clinical scales and Personality questionnaires 4.2.1. Structured Clinical Interview for DSM-IV Axis I Disorders, NonPatient Edition (SCID-NP) (First et al., 2007) An initial screening was carried out using the SCID-NP (First et al., 2007) to ensure that participants do not have any history of psychotic disorder. Basic demographic data were first collected and they were then asked about their history of psychopathology and for any psychotic experiences within the past one month from date of testing. Lastly, participants were then screened for any possible symptoms of delusions and hallucinations that were characteristics of schizophrenia. 27 4.2.2. Schizotypal Personality Questionnaire (SPQ) (Raine, 1991) The SPQ, which models after DSM-III-R criteria for schizotypal personality disorder, is a self-report questionnaire used for evaluating the presence of schizotypal personality features in participants. It has been widely used in different studies among different populations, such as in both western and non-western cultures, student and general population alike (e.g. Chen et al., 1997; Guo et al., 2011; Noguchi et al., 2008, Raine et al., 1994; Suhr & Spitznagel, 2001a). High internal consistency was found for the individual SPQ factors and the three factors were also consistently replicated in different studies. SPQ comprises of nine subscales which make up the three main factors (Raine, 1991). The three factors are: 1) Cognitive or perceptual deficits: which includes Idea of Reference, Odd beliefs / Magical thinking, Unusual perceptual experiences and Suspiciousness subscales 2) Interpersonal deficits: which includes Social Anxiety, No Close Friends, Constricted Affect and Suspiciousness subscales 3) Disorganized: which includes Odd Behaviors and Odd Speech subscales A total score and nine subscales scores may be obtained. In addition, scores of these three factors may be obtained by summating the subscales as stated above. 4.2.3. State-Trait Personality Inventory (STPI) (Spielberger, 1977) The STPI is an 80-item questionnaire which comprises of eight 10-item scales for assessing anxiety, anger, curiosity and depression as emotional states 28 and personality traits (Spielberger & Reheiser, 2004). The STPI anxiety, anger, curiosity and depression items describe either the presence or absence of these emotional states and the corresponding personality traits (Spielberger & Reheiser, 2004). For example, only the presence or absence of anxiety feelings is assessed by the state and trait anxiety items. The STPI is chosen for this study as it is time effective due to its capacity for measuring four fundamental emotional states and traits (i.e. anxiety, anger, depression and curiosity) without the need for multiple scales. Measuring these emotional vital signs is important for understanding an individual‟s psychological well-being. Variations in the intensity and duration of these emotional states provide essential information about one‟s mental and physical health, and help gain insight into recent events that may have lasting impact on one‟s life (Spielberger & Reheiser, 2004). For instance, a decrease in anxiety, anger and depression as personality traits can lead to improvement in psychological wellbeing (Spielberger & Reheiser, 2004), likewise an increase in curiosity (Spielberger & Reheiser, 2004). Moreover, the individual scales in STPI have high internal consistency ranging from .73 to .86 (Spielberger & Reheiser, 2004). Table 3 gives a summary of all the measures that were used in this study. 4.3. Neurocognitive assessment A battery of cognitive tests was used to assess participants‟ language and visual abilities, memory, attention, executive functions, working memory and motor speed. The cognitive battery comprises of 10 brief tests. The Brief 29 Assessment of Cognition in Schizophrenia (BACS; Keefe et al., 2004, 2008) comprises of six tests, and additional four supplementary tests were used as well. Following are the brief descriptions of all the neurocognitive tests used in the study. 4.3.1. Brief Assessment of Cognition in Schizophrenia (BACS) (Keefe et al., 2004, 2008) The BACS assesses the extent of cognitive impairments over multiple domains thought to be affected in schizophrenia (Kraus & Keefe, 2007). It includes brief assessments of four neurocognitive domains designated by the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) process: reasoning and problem solving, processing speed, verbal memory, and working memory (Keefe et al., 2008). Tests from the BACS and its corresponding MATRICS neurocognitive domains can be found in Table 2. The BACS takes about 30 minutes to complete and is easy to administer and score. BACS has demonstrated high reliability and concurrent validity with a standard battery tests in schizophrenia patients and healthy controls. It is also as sensitive to the cognitive deficits of schizophrenia as a standard 2.5 hour battery (Keefe et al., 2004). Furthermore, BACS also has clear functional relevance, as the composite score is strongly related to functional measures such as independent living skills (r = .45), performance-based assessments of everyday living skills (r = .56), and interview-based assessments of cognition in patients with 30 schizophrenia (r = .48) (Keefe, Poe, Walker, Kang, & Harvey, 2006; cited in Keefe et al., 2008). Following is the description of the six subtests of BACS: List Learning Test (Verbal Memory): Participants were read a list of 15 words and asked to recall as many words as possible. The procedure was repeated 5 times. This test is used to measure episodic memory functions. Outcome measure: total number of words recalled over 5 trials. Time: 7 minutes. Digit Sequencing Task (Working Memory): Participants were presented with clusters of numbers of increasing length. They were then asked to repeat the numbers in order, from lowest to highest. This test is designed to measure working memory. Outcome measure: total number of trials with all items in correct order. Time: 5 minutes. Token Motor Task (Motor Speed): Participants were given 100 plastic tokens of which they were to pick up one token each in each hand, simultaneously, as quickly as possible within 60 seconds and place them into a plastic container. This test measures motor speed. Outcome measure: the number of tokens correctly place in the container within 60 seconds. Time: 5 minutes. Verbal Fluency (Semantic Fluency): Participants were required to search their memory for words within a semantic category (e.g. animals, fruits, and vegetables). They were given 60 seconds to name as many items as possible within the given category. This task is designed to measure the intactness of the semantic system through semantic fluency. Outcome measure: number of words produced per category. Time: 3 minutes. 31 Symbol Coding (Attention and Processing Speed): Participants were given a key that contains unique symbols that were matched with numerals 1 – 9. They were to write numerals 1 – 9 which matches the symbols given on a response sheet. Ninety seconds were given to complete as many items as possible. The test is designed to measure attention, processing speed and short-term visual memory. Outcome measure: total number of correct responses. Time: 5 minutes. Tower of London (TOL) (Executive Functions/Reasoning and Problem Solving): Participants were shown 2 pictures, Picture „A‟ and Picture „B‟, simultaneously on each trial. Each picture contains 3 colored balls uniquely arranged on 3 pegs in each picture. Participants were required to accurately estimate the total number of moves the balls in Picture „A‟ have to make in order to make the arrangement of balls identical to that of Picture „B‟. They were to make the least possible moves and 20 seconds were given for them to make their decision for each trial. This test is designed to measure executive and problem solving abilities. Outcome measure: total number of correct trials. Time: 7 minutes. Table 2 BACS tests in the MATRICS neurocognitive domains1 MATRICS Neurocognitive Domain BACS Tests Processing speed Verbal Fluency Token Motor Task Symbol Coding Reasoning and problem solving Tower of London Verbal memory List Learning Working memory Digit Sequencing BACS, Brief Assessment of Cognition in Schizophrenia; MATRICS, Measurement and Treatment Research to Improve Cognition in Schizophrenia 1. Keefe et al., 2008; Kraus & Keefe, 2007 32 4.3.2. Benton Judgment of Line Orientation Test (BJLOT) (Benton, Hamsher, Varney, & Spreen, 1983) A modified version of BJLOT, Form H was used in this study. This task is designed to measure visual processing through examining visuospatial judgment, sensory perception and elementary perception. Participants were to identify the orientation of pairs of lines (i.e. lines that were partly erased) presented on a single page in comparison to an array of 11 lines shown immediately below. They were required to get at least 2 practice items correct before proceeding on to the test items. Outcome measure: total number of correct trials. Time: 7 minutes. 4.3.3. WAIS-III Matrix Reasoning Task (Wechsler, 1997) This task is modeled after Raven‟s Progressive Matrices. Items in the Matrix Reasoning Task consist of a sequence or group of designs, of which participants were required to fill in the missing design by choosing the best choice out of the 5 options provided. This task is used to control for premorbid intelligence and to measure abstract nonverbal reasoning ability. Outcome measure: total number of correct items. Time: 15 minutes. 4.3.4. Continuous Performance Test-Identical Pair (CPT-IP) (Cornblatt, Risch, Faris, Friedman, & Erlenmeyer-Kimling, 1988) The CPT-IP is a high processing load version of the continuous performance task paradigm. This version has an increased demand on working memory and thus the increased difficulty (Gooding et al., 2006). During the task, 33 stimuli were visually presented in relatively rapid succession on a computer screen and participants were required to respond when the same stimulus appears twice in a row (i.e. an identical pair). Each series of numbers were flashed on a computer screen at a rate of one per second. Participants were asked to click on the left mouse button when they see 2 identical numbers flashed continuously on the screen. The task is designed to tap on both attention and working memory as each stimulus must first be processed and then held in working memory until it can be compared to the next stimulus in order to determine if the 2 stimuli are exactly similar. This task has been widely used for measuring attention (Gooding et al., 2006; Lenzenweger et al., 1991). Outcome measure: the mean response sensitivity (d-prime) of the three conditions. Time: 10 minutes 4.3.5. Wisconsin Card Sorting Test-64 (WCST-64) (Axelrod et al., 1992, 1993, 1997) A computerized version of WCST, WCST-64 Computer Version 2 Research Edition, was administered in this study. Card stimuli were presented on a computer screen and participants were instructed to infer the matching principle based on the feedback provided (i.e. either „correct‟ or „incorrect‟ is flashed on the screen depending on participant‟s response). Participants were asked to sort card stimuli based on one of the three possible dimensions: color (red, green, blue, or yellow), shape (circle, triangle, star, or cross), and number (1, 2, 3, or 4). Through trial and error, they were to match the cards correctly to one of the four 34 key cards. The dimension (e.g. color) remains the same until the participants correctly performed ten consecutive sorts, thereafter the sorting dimension changes (e.g. shape). Participants were aware that the dimension will change, however they were not told of the exact number of correctly sorted cards to be achieved before the dimension shift. As the dimension changes from time to time, this tests the participants‟ ability to flexibly shift their mental set in order to correctly match the cards. WCST was used as it is one of the most robust tests for prefrontal cortex integrity and function which is usually measured through one‟s executive functioning (Gooding et al., 1999; Noguchi et al., 2008; Ruiz et al., 2008). In this version, 64 cards were used as compared to the standard number of 128, thus shorter time is needed to administer and it is also easier for participants to carry out the task. Outcome measure: numbers of categories achieved, perseverative errors, and number of trials to complete first category. Time: 10 minutes. 35 Table 3 Measures used in present study Measures SCIP-NP (First et al., 2007) Purpose Initial screening to ensure participants fulfill inclusion criteria No. of Items - Scoring - SPQ (Raine, 1991) Measures presence of schizotypal personality features 74 - Score range from 0 - 74 - Yes = 1 - No = 0 STPI (Spielberger, 1977) Measures anxiety, anger, curiosity, and depression as emotional states and personality traits 80 - Direct score of 1 to 4 - Items testing for the absence of emotional feelings are reverse scored (i.e. responses to items that are marked 1, 2, 3, or 4 are scored 4, 3, 2, or 1, respectively) - Rating of 4 indicates high level of certain emotion - Score is the sum of the direct- and reverse-scored items in each measure BACS (Keefe et al., 2004, 2008) Assess the extent of cognitive functions in Schizophrenia 6 Subtests: - List Learning Test - Digit Sequencing - Token Motor Task - Verbal Fluency - Symbol Coding - Tower of London Refer to Section 4.3.1. for details on scoring for each subtest. BJLOT (Benton et al., 1983) Measures Visual Processing - 5 practice items - 60 items (30 original test items and their mirror images) Score range from 0 – 30 WAIS-III Matrix Reasoning Task (Wechsler, 1997) Measures abstract nonverbal reasoning ability - 2 practice items - 35 test items. - Score range from 0 – 35 - Correct items = 1 - Incorrect items = 0 CPT-IP (Cornblatt et al., 1988) Measures attention and working memory - Three 150-trial conditions with increasing difficulty (i.e. 2-, 3-, and 4-digit conditions) - 30 target pairs in each condition - 30 “catch” trials (i.e. 2 similar but not identical successive stimuli - 90 trials that are not similar - Mean response sensitivity (dprime) of the 3 conditions 36 Measures WCST-64 (Axelrod et al., 1992, 1993, 1997) Purpose Measures executive functioning No. of Items 64 Scoring - Number of categories achieved - Number of perseverative errors - Number of trials to complete 1st category 4.4. Procedure Participants from the general population, recruited through advertisement placed in local newspapers, were invited to take part in this study at IMH. This is a single visit study which lasted for about two hours. An initial screening was conducted through the phone to ensure that participants fulfill the criteria as stated in Section 4.1. They were then scheduled for an assessment at IMH. Upon arrival at IMH, participants were first screened to ensure that they fulfill all criteria. Participants were tested in person by trained research assistants on all the procedures involved in the study. Informed consent was conducted before the start of the assessment in order for participants to fully understand the purpose of the study, the procedures involved and the possible risks and benefits. Socio-demographic data were collected as well. SCID-NP edition was then administered to ensure that participants do not have any psychotic disorders, history of alcohol or drug abuse, and presence of any neurological disease. After which, they were assessed on neurocognitive functions through a battery of cognitive tests such as BACS, BJOLT, Matrix Reasoning, CPT-IP, and WCST. Finally SPQ and STPI were administered and they were allowed to take as much time as needed to complete both questionnaires. Upon completion of the whole assessment, participants were reimbursed S$70 as inconvenience fees. 37 4.5. Statistical Analyses All statistical analyses were performed with Predictive Analytics Software (PASW) – PC version 18.0 for Windows (SPSS, Chicago, USA). Descriptive statistics including mean and standard deviation (SD) for continuous variables, and frequencies for categorical variables were computed for demographic variables of the study sample. Cluster analysis was used to determine the factor structure underlying schizotypal personality, as well as to identify the number of SPQ factors that may be present. This clustering technique was used due to its capacity in measuring the interrelationship of participants‟ responses to measures of symptoms. It takes into account that an individual may score highly on one or more dimensions. Univariate analysis of variance (ANOVA) was used to compare the mean scores of SPQ for schizotypal clusters and post-hoc pairwise comparisons were performed in case of significant effects in one-way ANOVA. Cronbach‟s alpha was conducted to explore the internal consistency of the SPQ factors. Nonparametric correlation analyses such as Kruskal-Wallis and MannWhitney U tests were then used to identify for possible associations between schizotypal clusters with neurocognitive functions and STPI. As for assessing possible relationships between neurocognitive functions and schizotypal clusters within each SPQ factors, Pearson‟s correlations were computed. Lastly logistic regression and multiple regression analyses were performed to identify the best STPI component that predicts the schizotypal clusters within each SPQ factor. Statistical significance was set at p < .05. 38 5. Results 5.1. Descriptive statistics In this study, 198 healthy English speaking Singaporean Chinese were sampled from the general population. Three participants were excluded due to missing data and the remaining sample comprised of 195 participants (112 males and 83 females). The mean age for males was 26.3 years (SD = 6.9) and 31.0 years (SD = 10.5) for females. The average years of education for males was 14.0 years (SD = 2.2) and 13.5 years (SD = 2.4) for females. 5.2. Cluster Analysis In previous cluster analysis studies of schizotypal traits, a four-cluster model is commonly found among participants (Williams, 1994; Loughland & Williams, 1997; Suhr & Spitznagel, 2001a; Barrantes-Vidal et al., 2002). To identify the number of clusters present in this study, a first cluster analysis (agglomerative hierarchical cluster analysis using Ward‟s procedure) was conducted with participants. However visual inspection of the dendrogram, a tree diagram, did not clearly support a four-cluster solution as hypothesized. Therefore, a two-way cluster analysis was further conducted. A two-way cluster analysis is where two hierarchical linear cluster analyses are performed on the groups and the features of the groups (StatSoft, 2011). In this study, two-way cluster analysis was performed on participants and the 74 SPQ items. Clustering both participants and SPQ items simultaneously may be useful in uncovering meaningful patterns of clusters. 39 5.2.1. Clusters for Participants A heat map, a graphical representation of data where values in a twodimensional table are represented in colors, was generated from the two-way cluster analysis, yielding a three-cluster solution (see Appendix A). To ensure that the clusters were significantly different, ANOVA was carried out with the participant clusters as independent variable and the Total SPQ score as dependent variable. Results showed that the clusters were significantly different, F(2, 192) = 293.39, p < .001 and post hoc tests further supported this finding. Cluster 1 consists of 87 participants who scored low on the SPQ; this is the „low schizotypy‟ cluster. While in Cluster 2, 90 participants were identified as scoring high on positive items; hence they are the „high positive schizotypy‟ cluster. Lastly, cluster 3 which consists of only 18 participants were found to score high on both positive and negative scales, making them the „high positive/negative schizotypy‟ cluster. The finding did not support the hypothesis of a four-cluster solution (i.e. with a missing high negative schizotypy cluster). Details of the clusters are presented in Table 4. 5.2.2. SPQ Factors Factorial structure of the SPQ was found to vary from studies to studies due to sample-specific characteristics (Compton et al., 2009). The 3-factor structure which is commonly replicated in previous studies (Chen et al., 1997; Raine et al., 1994; Reynolds et al., 2000) however may not best represent the Singapore Chinese population in this study. 40 From the heat map generated from the two-way cluster analysis, four main factors were identified (see Appendix A). To ensure consistency among the items in each new factor, internal reliabilities were tested. Reliabilities for the new factors ranged from .74 to .84, showing high consistency among the items. The first cluster named as „Referential Thinking‟, comprises of 11 items that are mainly positive such as Idea of Reference, Odd beliefs or Magical thinking, and Suspiciousness. The second cluster which comprises of 11 items from Social Anxiety, Constricted Affect, and No Close Friends, is the „Anxiety‟ cluster. The third cluster comprises of 18 items mainly from positive subscales such as Idea of Reference, Odd beliefs and Disorganized Speech and Behavior. This is the „Social Interaction Deficit‟ cluster. The remaining 34 items which fall into the final cluster, however did not seem to have a specific theme. Thus this is the „Undetermined‟ cluster, which will not be included in the second part of this study in identifying possible associations between clusters, neurocognitive functions and the STPI. The new SPQ factors can be found in Appendix B. 41 Table 4 Demographic data based on schizotypy clusters: mean (SD) Low High Positive (Cluster 1) (Cluster 2) N Age Education level Gender (Male/Female) Handedness (Left/Right/Both) 87 29.8 (9.6) 13.6 (2.5) 42/45 5/82/0 90 27.5 (8.3) 14.0 (2.1) 54/36 17/73/0 High Positive/Negative (Cluster 3) 18 25.7 (7.3) 13.9 (2.2) 16/2 3/14/1 New SPQ Factors Factor 1: Referential Thinking Factor 2: Anxiety Factor 3: Social Interaction Deficit Factor 4: Not Otherwise Specified Total SPQ 1.9 (1.4) 1.1 (1.4) 0.84 (1.3) 0.41 (0.84) 4.3 (3.4) 5.9 (2.0) 3.7 (2.7) 4.3 (2.9) 3.1 (2.7) 17.0 (5.8) 7.2 (1.7) 7.9 (1.7) 7.9 (3.7) 9.4 (4.4) 32.5 (7.2) 5.3. Associations of Clusters and SPQ Factors with Neurocognition and STPI Upon identifying the schizotypal clusters and SPQ factors, investigation of possible associations with neurocognitive functions and STPI in individual clusters and factors by means of correlation and regression analyses were then carried out. 5.3.1. Schizotypal Clusters As mentioned above, three clusters namely low, high positive, and high positive/negative schizotypy were found. Nonparametric correlation analyses were carried out due to different sample sizes across the three clusters. These analyses were used for uncovering any possible associations between individual schizotypal clusters with neurocognitive functions and STPI. Logistic regression 42 was also conducted to identify the personality trait or state that best predicts the individual schizotypal cluster. 5.3.1.1. Neurocognition Kruskal-Wallis tests were conducted to evaluate differences among the three schizotypal clusters on median change in the different neurocognitive tasks. In general, no significant relationship was found between the clusters and the neurocognitive tasks except for a significant result found between BACS Tower of London (TOL) and the schizotypy clusters, χ2 (2, N = 195) = 6.79, p = .03. Further pairwise comparisons among the three clusters were then carried out to determine the pair of clusters that were contributing to the significant results. Mann-Whitney U tests were conducted and the results indicated a significant difference between the low and high positive/negative schizotypal clusters. However this significant result, ɀ = -2.39, p = .02, was not in the expected direction as to prior studies. In prior studies, people with low schizotypy scores were found to perform better on tasks that measure executive functioning as compared to people high on schizotypy (Suhr & Spitznagel, 2001b; Ruiz et al., 2008). Instead the Low schizotypy cluster had an average rank of 49.83, while the high positive/negative schizotypy cluster had an average rank of 68.33, meaning that people who scored higher on schizotypy performed better on TOL. However, the correlation between TOL and clusters was ρ = .18, which indicates a rather weak relationship between schizotypy and executive functioning. Thus the current finding of high schizotypal individuals having better executive functioning, which 43 contrasts with the common findings of poorer executive functioning in high schizotypal individuals, may not be the case due to the weak association between TOL and schizotypy clusters. 5.3.1.2. STPI Kruskal-Wallis tests were conducted to evaluate the differences among the three schizotypal clusters on non-schizotypal personality traits as measured by STPI. Significant results were found on almost all state and trait items except for state curiosity and trait curiosity (Table 5). Hence further pairwise comparisons were carried out in order to identify the pairs of clusters contributing to the significant results. Post hoc analyses using Mann-Whitney U tests revealed that the significant findings were mainly due to differences between the low and the two high schizotypy clusters, whereas no difference was found between high positive and high positive/negative schizotypy clusters. The low schizotypy cluster scored lower on the STPI items as compared to high positive and high positive/negative schizotypy clusters (Figure 2). Since no difference was found between the two high schizotypy clusters, the two clusters were then collapsed and a MannWhitney U test was conducted for the low and the collapsed high schizotypy clusters. Significant findings were present for all state and trait items except for state curiosity and trait curiosity. Results were in the same direction as before collapsing the two high schizotypy clusters. The collapsed high schizotypy cluster was found to score higher on all state and trait anxiety, anger and depression 44 scales as compared to the low schizotypy cluster, while no difference was found for state and trait curiosity (Figure 3). Results show that people high on schizotypy are likely to be more anxious, depressed and angered easily as compared to low schizotypal individuals. Table 5 Kruskal-Wallis tests showing differences between clusters on STPI subscales STPI χ2 Df P Least significant differencea, p State Anxiety 16.9 2 2>1 Curiosity 1.07 2 .586 1,2>3 Anger 9.46 2 .009 3>2>1 Depress 9.75 2 .008 3>2>1 Total 9.92 2 .007 3>2>1 Trait Anxiety 37.1 2 2>1 Curiosity .68 2 .712 1,2>3 Anger 23.0 2 2>1 Depress 32.5 2 2>1 Total 49.4 2 2>1 a Post-tests show what clusters differ significantly. They are presented in ascending or descending order according to the mean ranks. To further investigate which personality state or trait of the STPI best predict the schizotypal clusters, logistic regression was conducted. For low and high positive schizotypy clusters, no significant result was found, which shows that none of the STPI components predicted these two clusters. As for high positive/negative schizotypy cluster, it was found that only trait anxiety best differentiated this cluster from the other two, χ2 (df = 1) = 10.32, p = .001. This result indicates that if one were to score high on subscale trait anxiety, the person is also more likely to exhibit schizotypal traits (Table 6). Thus people who are 45 innately more anxious, rather than anxiety caused by situational circumstances, may more likely exhibit schizotypal traits. Table 6 Logistic regression analysis of high positive/negative schizotypy cluster with STPI Predictor Β S.E. β Wald‟s Df p eβ 2 χ Constant -5.839 1.216 23.059 1 < .001 .003 STPI Trait .170 .053 10.321 1 .001 1.186 Anxiety Mean Note. Cox & Snell R2 = .057, Nagelkerke R2 = .122. All statistics reported herein use 4 decimal places in order to maintain statistical precision. 100.0000 90.0000 80.0000 70.0000 60.0000 50.0000 40.0000 30.0000 20.0000 10.0000 .0000 Low High Positive High Positive/Negative STPI Figure 2. Mean values of each STPI subscales for the schizotypy clusters Mean 46 100.0000 90.0000 80.0000 70.0000 60.0000 50.0000 40.0000 30.0000 20.0000 10.0000 .0000 Low High STPI Figure 3. Mean values of each STPI subscales for low and collapsed high schizotypy clusters 5.3.2. New SPQ Factors Through two-way cluster analysis (refer to section 5.2.2.), three main factors, namely referential thinking, anxiety, and social interaction deficit were found. Due to a lack of cohesive theme for the fourth factor, it was excluded for further analysis. Thus correlation and regression analyses were used for the first three factors in search of any possible associations between neurocognitive functions and STPI. 5.3.2.1. Neurocognition Pearson‟s correlation coefficients were first calculated between the new SPQ factors and neurocognitive functions using the entire sample (Table 7). No significant correlation was found between referential thinking and the 47 neurocognitive tasks. For the new factor anxiety, it was found positively correlated to TOL. This shows that participants who scored high on anxiety factor tended to perform better on TOL. As for the social interaction deficit factor, it was positively correlated to Token Motor Task and TOL. Results suggest that people who scored high on social interaction deficit items tended to perform better on Token Motor Task and TOL Table 7 Pearson‟s correlations between new SPQ factors and neurocognitive tests Neurocognitive Tests Factor 1, Factor 2, Factor 3, Referential Thinking Anxiety Social Interaction Deficit BACS Verbal Memory .062 .073 .064 Digit Sequencing -.105 .011 .016 Token Motor Task .092 .105 .150* Semantic Fluency .016 -.011 .096 (Animals) Symbol Coding -.022 .103 .081 Tower of London .074 .157* .244** Benton Line Orientation -.089 .014 .076 Matrix Reasoning -.092 -.027 -.003 CPT-IP (Average D-.054 -.119 .042 Prime) WCST (No. of -.039 -.026 -.031 perseverative error) WCST (Categories .017 -.015 .028 completed) **. Correlation is significant at the .01 level (2-tailed). *. Correlation is significant at the .05 level (2-tailed). Given that different people with schizotypal personality may exhibit different schizotypal traits and neurocognitive abilities, an in-depth analysis was further carried out to probe for possible relationships between the new SPQ factors and neurocognitive functions under each schizotypal cluster (Table 8). 48 Through within-cluster analysis, this helps to identify neurocognitive impairments and emotional temperaments that might most likely be found in the high positive/negative schizotypal cluster. In turn, this aids in identifying potential endophenotypes and etiological factors given that this cluster is seen as a proxy to the subclinical deviances of schizophrenia spectrum personality disorders based on the continuum model. From here, a form of classification system could be set up and extended in the future through future research. Based on the results, in the low schizotypy cluster, referential thinking was positively correlated with CPT-IP, while negatively correlated to the number of perseverative errors for WCST. On the other hand, social interaction deficit was found positively correlated with Verbal Memory, Digit Sequencing and Matrix Reasoning, while negatively correlated with WCST. In high positive schizotypy cluster, referential thinking was negatively correlated with Digit Sequencing and Symbol Coding. Under this cluster, social interaction deficit was positively correlated with Token Motor Task and TOL. Lastly in the high positive/negative schizotypy cluster, referential thinking was found to be negatively correlated with Matrix Reasoning, whereas social interaction deficit was negatively correlated to TOL and Matrix Reasoning. This shows that participants, who score higher on schizotypal features such as referential thinking and social interaction deficit, may perform worse on TOL and Matrix Reasoning as compared to those who score low on these factors. No significant finding was found between schizotypal clusters and anxiety factor. 49 It is also important to note that these Pearson‟s correlation coefficients were significant only before Bonferroni adjustment was made to control for Type I error. Although no significant correlations were found after adjustment, it is still important to note that possible underlying associations may be uncovered given a larger sample. Table 8 Pearson‟s correlations between new SPQ factors and neurocognitive tests within individual schizotypal cluster Schizotypal Neurocognitive Tests Factor 1, Factor 2, Cluster Referential Anxiety Thinking Low, N = 87 High Positive, N = 90 BACS Verbal Memory Digit Sequencing Token Motor Task Semantic Fluency (Animals) Symbol Coding Tower of London Benton Line Orientation Matrix Reasoning CPT-IP (Average DPrime) WCST (No. of perseverative error) WCST (Categories completed) BACS Verbal Memory Digit Sequencing Token Motor Task Semantic Fluency (Animals) Symbol Coding Tower of London Benton Line Orientation Matrix Reasoning Factor 3, Social Interaction Deficit .104 .005 .089 .085 .033 .141 .147 -.010 .239* .218* .024 .073 -.004 -.121 .032 .037 .222* .097 .146 .124 .043 -.049 .009 .118 .186 .281** .199 -.219* -.071 -.217* .100 -.010 .115 -.071 -.223* -.040 -.169 .132 .080 -.004 -.062 -.011 .076 .220* .113 -.242* -.094 -.107 -.197 .095 .008 .082 -.043 .082 .362** .179 .009 50 CPT-TP (Average DPrime) WCST (No. of perseverative error) WCST (Categories completed) High Positive/Negative N = 18 BACS Verbal Memory Digit Sequencing Token Motor Task Semantic Fluency (Animals) Symbol Coding Tower of London Benton Line Orientation Matrix Reasoning CPT-TP (Average DPrime) WCST (No. of perseverative error) WCST (Categories completed) -.192 -.125 .131 .094 .028 .019 -.056 -.104 .101 -.008 -.206 -.291 -.136 -.219 -.057 .285 -.147 -.116 -.132 -.172 -.056 -.054 .151 -.163 -.530* .004 -.008 -.070 -.136 -.080 .124 -.034 -.591** .150 -.532* .035 .463 -.005 .299 -.247 .396 -.378 Note: Correlation coefficients are significant before Bonferroni adjustment for Type 1 error. **. Correlation is significant at the .01 level (2-tailed). *. Correlation is significant at the .05 level (2-tailed). 5.3.2.2. STPI To understand the relationship between the new SPQ factor and STPI, regression analysis was performed. Regression analysis was chosen so as to investigate which personality state or trait of the STPI best predicts the new SPQ factors. Results show that state anxiety and trait anxiety predict referential thinking with trait anxiety being the stronger predictor. Likewise, trait anxiety also predicted the anxiety factor. Lastly, trait curiosity, trait anger and trait depression, all positively predicted the social interaction deficit factor with trait depression being the stronger predictor. These results suggest that individuals 51 who are innately more anxious are likely to have more referential thoughts and are definitely more anxious. Results also suggest that individuals who are more depressed regardless of circumstances are likely to face more problems while interacting with others. A summary of the regression coefficients can be found in Table 9. Table 9 Regression coefficients between STPI and new SPQ factors Subscales of STPI Factor 1, Factor 2, Referential Thinking Anxiety State Anxiety Curiosity Anger Depress Trait Anxiety Curiosity Anger Depress Factor 3, Social Interaction Deficit .192* .010 -.060 -.195 .161 -.025 -.039 -.150 .081 .002 .028 -.014 .250* .176 .072 .235 .275* -.022 .072 .169 .011 .227* .218** .303* **. Correlation is significant at the .01 level (2-tailed). *. Correlation is significant at the .05 level (2-tailed). Similar to previous section 5.3.2.1., within-cluster analysis was further performed so as to identify the personality state or trait that predicts the SPQ factor under each schizotypal cluster. A summary of the results can be found in Table 10. This is helpful in identifying high risk schizotypal individuals based on their dominant personality state or trait and their scores for the SPQ factors. Under the low schizotypal cluster, results show that state curiosity and trait anxiety positively predict referential thinking, while state anger, trait curiosity and trait depression negatively predict referential thinking. Among these predictors, 52 trait anxiety best predicts referential thinking in the low schizotypy cluster. As for the anxiety factor, trait anger best predicted this factor. On the other hand, state curiosity and trait anger positively predicted social interaction deficit factor. For high positive schizotypal cluster, state anxiety best predicts referential thinking. Trait anxiety was found to positively predict the anxiety factor, while trait curiosity negatively predicts anxiety factor. Trait curiosity is the stronger predictor for the anxiety factor under the high positive schizotypal cluster. Lastly, trait anger was found to positively predict the social interaction deficit factor under the high positive schizotypal cluster. Unfortunately due to the very small sample size, no significant predictor was found to predict the individual SPQ factors under the high positive/negative schizotypal cluster. Table 10 Regression coefficients between STPI and new SPQ factors within individual schizotypal cluster Schizotypal Subscales of Factor 1, Factor 2, Factor 3, Cluster STPI Referential Anxiety Social Interaction Thinking Deficit Low, State N = 87 Anxiety Curiosity .148*** .082*** Anger -.157** Depress Trait Anxiety .165*** Curiosity -.134** Anger .099** .083* Depress -.108* High Positive, N = 90 State Anxiety Curiosity Anger .104* - - - 53 Depress Trait Anxiety Curiosity Anger Depress High Positive/Negative N = 18 State Anxiety Curiosity Anger Depress Trait Anxiety Curiosity Anger Depress - - - - .149* -.182** - .150* - - - - - - - ***. Regression coefficient is significant at the .001 level (2-tailed). **. Regression coefficient is significant at the .01 level (2-tailed). *. Regression coefficient is significant at the .05 level (2-tailed). 54 6. Discussion The intention of this study was to examine relationships between individual schizotypal clusters with neurocognitive functions and non-schizotypal personality traits. The overarching aim was to identify aspects of schizotypy that will help elucidate the heterogeneity of schizotypal traits in an Asian population and, by way of identifying potential cognitive endophenotypes, in future assist the chances of identifying high risk individuals. In the present study, a three-cluster solution (low, high positive, and high positive/negative schizotypy clusters) and three new SPQ factors were found through cluster analysis. In addition, different associations were found between individual clusters with neurocognitive functions and non-schizotypal personality traits as measured by the STPI. However, associations between schizotypal clusters and neurocognitive measures need to be interpreted with caution due to multiple comparisons which increased the danger of Type I error. This is the first study to conduct such in-depth exploration of individual schizotypal clusters and their associations with a wide range of neurocognitive measures, emotional states and personality traits in any population. This study is also the first to attempt a classification of schizotypy. Moreover, it is conducted in a non-Caucasian, Asian population as opposed to the usual Western college-age student population. Findings are therefore specific and may serve as a basis for understanding schizotypy in the Asian population. Lastly, new statistical technique, namely two-way clustering analysis, was performed. This is the first 55 study to use a heat map approach in the identification of schizotypal clusters and SPQ factors. 6.1. Schizotypal clusters and SPQ factors Along with a growing number of studies, cluster analysis is used in the present study for clustering similar individuals together. Cluster analysis provides clear support for the multidimensional nature of schizotypy (Mason, Claridge, & Williams, 1997). This approach considers individuals as having multiple schizotypal features which do not allow them to fall „cleanly‟ into distinct groups as opposed to factor analysis which groups individuals based on their responses to measures, and thus into distinct groups. According to research studies using cluster analysis (Loughland & Williams, 1997; Suhr & Spitznagel, 2001a, b; Williams, 1994), we expect to find a four-cluster solution in the present study. However the two-way cluster analysis revealed a three cluster solution (low, high positive, and high positive/negative schizotypy clusters) without any high negative cluster. Although the heat map showed a slight possibility of a four-cluster solution, a three-cluster solution was more favorable as further division of clusters resulted in more comparisons and increases the danger of Type I error. The results from ANOVA also supported the presence of three distinct clusters. An important difference of this study is that this is the first time a two-way cluster analysis was examined within an Asian sample, and therefore, subject to replication, these three clusters may be seen as unique to this population. 56 The heat map also revealed three concrete SPQ factors (referential thinking, anxiety, and social interaction deficit) that are different from the traditional three-factor schizotypy structure. An interesting finding was that these new SPQ factors are somewhat similar to the characteristics of other personality disorders. For instance, the new SPQ factor anxiety, made up of negative features such as constricted affect, social anxiety and preference of being alone (refer to Appendix B for full SPQ items), is similar to Schizoid Personality Disorder. According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR; American Psychiatric Association, 2000), Schizoid Personality Disorder is a pervasive pattern of detachment from social relationships and a restricted range of expression of emotions in interpersonal settings, where individuals do not desire or enjoy close relationships and chooses solitary activities. For the social interaction deficit factor, it contains items that are similar to Paranoid Personality Disorder, characterized by pervasive distrust and suspiciousness of others such that their motives are interpreted as malevolent (DSM-IV-TR; American Psychiatric Association, 2000). Thus, these new SPQ factors may provide some form of criteria that is helpful in distinguishing between closely related personality disorders. The differences in number of SPQ factors found in present study may be due to different measurements used in schizotypy studies. For instance, Suhr and Spitznagel (2001a, b) used SPQ along with PAS and MIS; Williams (1994) used other measures such as MIS, PhAS, SAS and STA, while the present study used the SPQ to identify psychometrically defined schizotypal individuals. The 57 combination of multiple measurements used may consequently improve the overall effectiveness of differentiating schizotypal features since different measurements are better at capturing different schizotypal features (refer to table 1). For instance, the use of PhAS and SAS along with SPQ might improve the chance of detecting negative schizotypal features, thus identifying the high negative schizotypy cluster which explains for the four-cluster solution (e.g. Williams, 1994). Therefore, differences in measurements may justify for the fewer concrete SPQ factors found in the present study. 6.2. Associations of schizotypal clusters with Neurocognition and STPI 6.2.1. Neurocognition Following the continuum model, we hypothesized that psychometrically defined schizotypal individuals are likely to perform worse on most of the neurocognitive tasks due to possible cognitive impairments. No significant findings were found between individual clusters and specific neurocognitive functions except for high positive/negative schizotypes scoring better in TOL as compared to those low in schizotypy. This contrasts with previous studies reporting poorer executive functioning found in high schizotypy individuals (Suhr & Spitznagel, 2001b; Ruiz et al., 2008). A possible explanation accounting for this effect is the small high schizotypy group size and the statistical analysis that was carried out. With further in-depth analysis of each cluster‟s associations with neurocognitive measures under each SPQ factor (as shown in Table 4), high positive/negative cluster did perform worse on TOL under the social interaction 58 deficit factor. However due to a small sample size of 18 schizotypes in the high positive/negative cluster, the negative correlation might have been masked. Moreover, the correlation between TOL and clusters was also rather weak. Hence, the finding of worse TOL performance in high positive/negative schizotypy cluster under the social interaction deficit factor may have been overlooked and future research could address this finding. 6.2.2. STPI Similarly based on the continuum model, we expect psychometrically defined schizotypal individuals to report higher level of negative emotional states and traits such as anxiety and depression. The present study found significant results for all state and trait items, except for state and trait curiosity, with high schizotypy clusters scoring high on these STPI items. Thus, this supports the hypothesis of psychometrically defined schizotypes reporting higher level of emotional states and personality traits such as anger, anxiety and depression. Unfortunately no specific traits were associated with individual schizotypal clusters. Consistent with prior research, schizotypy is generally associated with increased levels of trait anxiety and depression (Braunstein-Bercovitz, 2000; Lewandowski et al., 2006; Mohanty et al., 2008). Higher levels of negative affects as measured by self-report scale may indicate impairment in emotion processing particularly in relation to emotional experiences. Emotion processing has been conceptualized to involve: 1) cognitive appraisal and perception, 2) 59 expression, 3) physiological arousal, and 4) subjective experience (Plutchik, 1984; cited in Phillips & Seidman 2008). Studies have shown that undergraduates with positive schizotypal features endorse items that suggest higher levels of experienced emotion as compared to controls, in the form of increased emotionality, intensity and increased negative affect (Berenbaum, Boden, Baker, Dizen, & Thompson, 2006; Kerns, 2005). In addition, individuals displaying higher levels of positive schizotypy tended to report increased emotional confusion and ambivalence to emotions (Kerns, 2006). On the other hand, negative schizotypy is associated with decreased reported emotionality, increased confusion and trouble identifying the experienced emotion (Kerns, 2006). The present finding of a high schizotypy cluster (i.e. collapsed across high positive and high positive/negative clusters) reporting higher levels of anxiety, anger and depression is in line with previous findings. To further identify if any specific personality state or trait best predicts the individual schizotypal cluster, logistic regression was carried out. It was found that trait anxiety best predicts the high positive/negative schizotypal cluster. This means that high schizotypal individuals report higher levels of anxiety in most circumstances, as compared to low schizotypy individuals. This finding is in line with previous research on high schizotypy group demonstrating higher levels of trait anxiety, though not depression (Lenzenweger et al., 1991). Unfortunately, no specific STPI component was found to predict high positive schizotypy. It is also important to note that emotional disturbance is also a core feature in schizophrenia. DSM-IV-TR contains references to emotion disturbance in 60 schizophrenia, such as affective flattening, anhedonia, depression, anxiety and anger (American Psychiatric Association, 2000). Emotional disturbance found in schizophrenia and schizotypy further lends support to the idea of a continuum model. In summary, these findings suggest increased negative emotions such as anger, anxiety and depression present in psychometrically defined schizotypal individuals. 6.3. Association of SPQ features with Neurocognition and STPI 6.3.1. Neurocognition Interesting findings were found between the new SPQ factors and neurocognitive measures under each schizotypal cluster. In an overview based on the correlations between new SPQ factors and neurocognitive measures (Table 7), results showed the anxiety factor as positively correlated to TOL, whereas social interaction deficit factor was positively correlated to Token Motor Task and TOL. This means that individuals scoring high on anxiety factor are likely to do better on TOL, while individuals scoring high on social interaction deficit are likely to do better on Token Motor Task and TOL. As stated earlier, one of the aims of this study is to determine potential endophenotypes (i.e. neurocognitive functions) that might be found in both schizotypal individuals and individuals with schizophrenia spectrum disorders. Following the continuum model, individuals scoring high on most SPQ items may be viewed as high risk. Thus, neurocognitive impairments that are present in the high positive/negative schizotypal group may present as potential endophenotypes 61 and reveal potential etiological factors for schizophrenia and schizophrenia spectrum disorders. Hence, further within-cluster analyses were needed to examine possible relationships between SPQ factors and neurocognitive measures under each schizotypal cluster, with specific focus on high positive and high positive/negative schizotypal clusters (refer to Table 8). Under high positive schizotypal cluster, individuals scoring high on referential thinking performed poorer on Digit Sequencing and Symbol Coding. As for high positive/negative schizotypal cluster, individuals scoring high on referential thinking performed poorer on Matrix Reasoning, while individuals scoring high on social interaction deficit performed poorer on TOL and Matrix Reasoning. In contrast to prior findings, no significant association was found between neurocognitive measures and anxiety factor, a negative schizotypal factor, in all three schizotypal clusters. Although no significant results were found upon adjustment made to control for Type I error, these findings still form a meaningful trend and are consistent with prior research. For instance, high positive/negative schizotypy cluster performed poorly on almost all neurocognitive tests (BarrantesVidal et al., 2002; Chen et al., 1997; Gooding et al., 2006; Lenzenweger et al., 1991; Noguchi et al., 2008). With a larger sample for high schizotypy clusters, significant results may be present after adjustment for Type I error. Based on present findings, two potential endophenotypes may be present: working memory and social cognition. Impairments of working memory were demonstrated by poorer performance on Digit Sequencing and Symbol Coding in high positive 62 schizotypal individuals. Digit Sequencing measures working memory as it requires one to temporary hold the numbers that were recited and then mentally rearrange the numbers in ascending order. According to Baddeley‟s model of working memory (Baddeley, 1986; cited in Park & McTigue, 1997), information is temporarily maintained by an active attention control system known as the central executive, aided by modality-specific sub-systems such as the phonological loop and the visuo-spatial sketchpad. The phonological loop works with the central executive in maintaining auditory information in working memory by means of sub-vocal rehearsal in real time, such as in Digit Sequencing (Park & McTigue, 1997). On the other hand, the visuo-spatial sketchpad maintains and manipulates visual images, as in Symbol Coding. Symbol Coding also measures attention and speed of information processing, which were also found impaired in relatives of schizophrenia patients (Anselmetti et al., Snitz, MacDonald III, & Carter, 2006). Working memory deficits have been widely researched in schizophrenia patients and their unaffected relatives. There is abundant evidence on schizophrenia patients performing poorly on tests of working memory (Gold, Carpenter, Randolph, Goldberg, & Weinberger, 1997; Goldman-Rakic, 1994; Keefe, 2000; Park & Holzman, 1992). In a study by Silver, Feldman, Bilker, & Gur (2003), working memory was found as a core dysfunction in schizophrenia and is associated with impairments in cognitive, motor and emotional functions. In addition, unaffected relatives of schizophrenia patients are impaired in working memory performances. For instance, in a twin study which included 48 discordant 63 twin pairs and 8 concordant pairs for schizophrenia, performance on spatial working memory task decreased as genetic risk of schizophrenia increased (Cannon et al., 2000; cited in Donohoe, Goldberg, & Corvin,2009 ). In another study (Tuulio-Henriksson et al., 2003), it was found that relatives of multiplex families (families with more than one affected members) showed greater spatial working memory deficits than simplex family members but less significant verbal working memory. Deficits in working memory have been linked to dysfunctions of neural circuitry mediated by the frontal cortex (Goldman-Rakic, 1987; cited in Park & McTigue, 1997), which in turn were found responsible for executive function and attention deficits in relation to negative schizotypy symptoms (Dinn et al., 2002; Stuss & Alexander, 2000). The present findings, however, showed impairments of working memory, executive functioning, and attention associated with positive schizotypy such as increased levels of referential communication disturbances and positive thought disorders, which are in line with previous studies (Docherty & Gordinier, 1999; Docherty et al., 1996; McGrath, Chapple, & Wright, 2001; Nestor et al., 1998; Spitzer, 1993). Goldman-Rakic (1994) suggested that a breakdown in the working memory processes by which representational knowledge governs behavior may have resulted in the symptoms of schizophrenia. For instance, once working memory processes fail, behaviors become excessively dominated by the immediate environment rather than by a balance of current and past information. Hence working memory deficits may underlie positive symptoms such as thought disturbances and hallucination, via a mix of increased 64 distractibility, attentional disturbances and misinterpretation of causality (Goldman-Rakic, 1994). Thus, impaired working memory is associated with both negative symptoms and positive thought disorder. Another interesting finding is the poor performance in Matrix Reasoning in association with the high positive/negative schizotypy cluster under referential thinking. Matrix Reasoning taps non-verbal abstract problem solving and reasoning abilities. The ability to solve abstract problems, which is also viewed as an executive function process, is also controlled by the frontal lobes (Channon, 2004). In summary, poorer performances on these neurocognitive measures imply impairments in frontal lobe functions that play an important role in working memory, attention and problems solving abilities. Thus impairments of the frontal lobes may have a role in positive schizotypy symptoms such as referential thoughts and delusions. Social cognition deficits were demonstrated by the poorer performances on TOL and Matrix Reasoning by the high positive/negative schizotypal individuals under the social interaction deficit factor. This means that difficulties in social interactions which high schizotypal individuals face may be due to their decreased understanding of social situations as shown by deficits in abstract problem solving and planning abilities. Social cognition is a domain of cognition that involves the perception, interpretation, and processing of social information (Adolphs, 1999; cited in Anselmetti et al., 2009). Social behaviors involve different cognitive processes such as Theory of mind (ToM, the ability to judge the mental states of self and others), perception of social signs, attention, memory, 65 decision making, motivation, and recognition of facial expressions (Anselmetti et al., 2009). Social cognitive deficits have been found in schizophrenia patients through deficits in interpersonal skills as compared to healthy controls (Donahoe et al., 1990; Ikebuchi, Nakagome, & Takahashi, 1999; Mueser, Bellack, Douglas, & Morrison, 1991). For instance, in a study by Pinkham and Penn (2006), individuals in the schizophrenia group displayed deficits in neurocognition, social cognition and interpersonal skills as compared to healthy individuals. Neurocognitive impairments have been implicated in interpersonal skill deficits found in schizophrenia patients (Penn, Mueser, Spaulding, Hope, & Reed, 1995). In particular, deficits in memory, attention and cognitive flexibility as related to difficulties in problem solving (Green, Kern, Braff, & Mintz, 2000), and deficits in executive functioning, memory and verbal fluency related to poorer community living skills (Bartels, Mueser, & Miles, 1997; Green et al., 2000). Deficits in social functioning are also implicated before the onset of schizophrenia, such as in children and adolescents at risk of developing schizophrenia (Hans, Marcus, Henson, Auerbach, & Mirsky, 1992; cited in Penn, Corrigan, Bentall, Racenstein, & Newman, 1997), and first degree relatives of schizophrenia patients (Hans, Auerbach, Asarnow, Styr, & Marcus, 2000; cited in Couture, Penn, & Roberts, 2006). Hence, evidence from existing literature and present study‟s findings showed that schizophrenia patients, unaffected relatives and high risk individuals may have difficulty comprehending people‟s actions and words, leading to increased suspiciousness of others and thus avoidance of social interactions. 66 Therefore, poorer performance on TOL and Matrix Reasoning may reveal deeper problems in social perceptions and interactions in schizotypy. Hence, evidence of impairments in working memory and social cognition in schizophrenia, high risk groups and schizotypal individuals may underlie potential endophenotypes as it denotes shared behavioral effects of a common genetic vulnerability. Thus, it offers the possibility of identifying distal genetic diatheses to the complex symptomatology of schizophrenia. 6.3.2. STPI In overview, regression analysis was carried out to understand the relationship between the components of STPI with the new SPQ factors. As show in Table 9, trait anxiety is a strong predictor for both referential thinking and anxiety, positive and negative factor respectively. This suggest an anxiety component in the schizotypal scale, which is in line with previous studies that found a relationship between schizotypy scale and trait anxiety score (Gibbons & Rammsayer, 1999; cited in Braunstein-Bercovitz, 2000). Thus, findings of this study show that both positive and negative schizotypy are associated with anxiety, with it being more associated to negative than positive schizotypy as shown by the higher regression coefficient between trait anxiety and SPQ anxiety factor. On the other hand, trait depression was found to be the best predictor of social interaction deficit. This means that individuals who are innately more depressed are more likely to report having experienced difficulties while interacting with others as compared to individuals who are less depressed. Feeling 67 depressed may have many immediate implications for the production of skilled social behaviors such as slowed and delayed psychomotor behaviors (Sobin & Sackeim, 1997; cited in Segrin, 2000). These delayed psychomotor behaviors may include slowed speech, long response latencies, diminished eye contact and increased nervous gesturing. These behaviors are generally considered representative of poor social skills. Difficulty in concentration, feelings of worthlessness and social withdrawal that are common to depression could affect social behaviors and the desire to interact with others (Segrin, 2000). Hence it is not surprising that trait depression is a strong predictor of social interaction deficit factor. Similar to the previous section 6.3.1., one of the aims of this study is to uncover possible etiological factors of schizophrenia spectrum disorders through the study of schizotypy. Thus, within-cluster analyses were further performed to look for possible associations between SPQ factors and STPI components, especially in high positive and high positive/negative schizotypal clusters (Table 10). Unfortunately, no association was found between STPI and SPQ in the high positive/negative schizotypal cluster. This is possibly due to the very small sample size and restriction of range effects which reduced the sensitiveness of the test, leading to the lack of significant results. A larger sample may help to uncover significant associations. Under the high positive schizotypal cluster, significant findings were found between STPI and SPQ factors. Firstly, it was found that higher levels of state anxiety best predict high positive schizotypes who score high on items 68 measuring referential thinking. This means that under circumstances that may lead to delusional thoughts and referential ideas, such as upon noticing people whispering to one another, individuals high on such schizotypal traits are likely to experience heighten levels of anxiety. Secondly, lower levels of trait curiosity were found to predict high positive schizotypes who have higher scores on the anxiety factor. This means that high positive schizotypal individuals are more likely to have lower levels of curiosity towards people especially when they are nervous and anxious. For instance, they scored high on items such as “I find it hard to be emotionally close to other people” or “I feel very uneasy talking to people I do not know well”, at the same time reporting low on items of trait curiosity. This finding is consistent with the idea of Social anhedonia which was originally proposed by Meehl (1962, 1989; cited in Collins, Blanchard, & Biondo, 2005) as a core characteristic of schizotypy. Social anhedonia in schizophrenia represents loss of interest or pleasure and poor social functioning, which is similar to the negative features of schizotypy. These people tend to be indifferent to others, and thus the lower level of curiosity. Previous research also shown that social anhedonics have cognitive deficits in working memory (Gooding & Tallent, 2003) and executive functioning (Gooding et al., 1999; Tallent & Gooding, 1999). However no such relation was found in the present study. Lastly, high levels of trait anger were found to predict social interaction deficit in the high schizotypal cluster. This finding is consistent with studies which have reported a relationship between positive schizotypy and 69 aggressiveness (Lapworth et al., 2009; Seah & Ang, 2008) suggesting that increased perception of environmental cues as hostile and threatening leads to increased aggressiveness in high schizotypes and may, in turn cause avoidance, paranoia and suspiciousness of others. Even though within-cluster analysis led to smaller sample size and restriction of range effects, significant findings and similar patterns to previous studies were still found in the present study. 6.4. Implications of present study The outcome of the present study can be summarized as follows: 1) the use of two-way clustering analysis in identifying three different schizotypal clusters and new SPQ factors, and 2) the associations found between schizotypal clusters and SPQ factors with neurocognitive measures and STPI. There have been studies of schizotypy and its relations to neurocognitive functions and emotional states (Braunstein-Bercovitz, 2000; Lenzenweger et al., 1991). However, the present study went one step further by including a wider range of neurocognitive functions, emotional and personality traits in relations to individual schizotypal clusters and features. Thus this increases the likelihood of identifying other aspects of schizotypal personality that may indicate enhanced risk for schizophrenia, such as frontal lobe impairments implicated in positive schizotypy and deficits in abstract problem solving abilities leading to social interaction problems. The inclusion of emotional states and non-schizotypal personality traits in schizotypy studies are also useful for early identification of high-risk individuals. 70 A number of studies have consistently shown anxiety and depression to be found in individuals with higher level of schizotypy (Lenzenweger et al., 1991; Lenzenweger & Loranger, 1989; Lewandowski et al., 2006). Furthermore, heightened levels of negative emotions and personality traits in the prodromal stage of schizophrenia is also related to increased risk of transition into psychosis (Yung et al., 2003; cited in Lewandowski et al., 2006). Individuals who reported high level of schizotypal features could be in distress, and such anxiety and negative disturbances will only hasten the transition (Lewandowski et al., 2006). Hence attempts to uncover possible associations between emotional states and traits in schizotypy are important as this improves the chances of identifying troubled individuals and forestalling transition into full-blown psychosis. Thus the present findings and prior studies show that the understanding of prodromal individuals should include attention to emotional states and traits such as anxiety and depression as they may have negative impact on schizotypy. Another implication is that findings in this study may be unique to this Asian population that has been shaped by exchanges between the East and the West cultures. Compared to other Asians such as Japanese and Chinese, Singaporeans are still more open to and well educated on issues of mental illness. However due to urbanization and greater stress, Singaporeans may therefore experience higher levels of anxiety, depression and frustration, as well as the lack of interest in interacting with others. The greater stress experienced could also affect memory and attention due to overwhelming inputs from the environment. Hence this study provides a new point of view for understanding schizotypy in 71 Singapore. Lastly, these new SPQ factors may possibly identify individuals who are prone to other personality disorders rather than schizotypy per se, as shown through the similarities found between the new factors and other personality disorders (refer to section 6.1.). Thus these SPQ factors go beyond the traditional three-factor schizotypal personality. 6.5. Study limitations and future directions The present study is however not without limitations. One limitation is the small sample size which generated an even smaller group of high positive/negative schizotypy cluster. Given that multiple comparisons were made between clusters, neurocognitive measures and STPI components, results were rendered insignificant after Bonferroni adjustment was made to correct for Type I error. In addition, there is also restriction of range effects when within-cluster analyses were carried out on SPQ with neurocognitive measures and STPI within individual schizotypal cluster. As multiple comparisons and within-cluster analyses were necessary to provide a comprehensive picture of schizotypy and its relations to neurocognition and personality traits, a larger sample will be helpful for future studies. Another limitation is the use of relatively new statistical technique and measurement, such as two-way clustering analysis and STPI. The drawback of using new statistical techniques and measuring scale is that it makes comparisons to prior studies difficult. Previous clustering analysis studies either use a simple agglomerative hierarchical cluster analysis (Ruiz et al., 2008) or K-means 72 iterative cluster analysis (Barrantes-Vidal et al., 2002; Suhr & Spitznagel, 2001a, b). K-means clustering is when the number of clusters is specified so as to support a prior hypothesis (StatSoft, 2011). Given that this study is exploratory in nature, the use of new techniques such as two-way cluster analysis will be more suitable. Moreover, it adds new information to existing findings even though a full classification system is yet to be formed through this study. Future research may make use of findings from this study as a starting point for building a more comprehensive classification system in understanding schizotypal personality. For instance, other non-schizotypal personality inventories, emotional states and traits questionnaires should also be included to help understand the role of emotional states and personality traits in schizotypy. Also, interviews can be used in place of self-report questionnaires in detecting individuals who exhibit schizotypal features as interviewers can better probe and are more sensitive to odd behaviors and speech which are difficult to elicit through questionnaires (Kremen et al., 1998). Based on present findings of associations between schizotypy, neurocognitive performances and self-reports of emotional states and personality traits, a classification system for categorizing schizotypes may be possible in the future along with the help of formalized measures and genetic research on schizophrenia. Given that individuals in the same cluster are genetically more homogenous base on similar neurocognitive deficits and emotional temperaments, this provides important avenues for future research in locating possible genetic foci within each cluster. The added information on different genes causing different symptoms and deficits in 73 schizotypy can help establish specific preventive and treatment measures for diverse groups of high-risk individuals. Lastly, future studies can also look into the impact of frontal lobe dysfunctions before the onset of schizophrenia given that most neurocognitive deficits found among high schizotypal individuals were related to frontal lobe functions. 6.6. Conclusions In conclusion, the present study found some significant associations between schizotypy, neurocognition and non-schizotypal personality traits. Individuals exhibiting positive schizotypal features were found to perform poorer on measures of working memory, executive functioning and attention. Impairments in these areas suggest frontal lobe dysfunctions even before the onset of schizophrenia. An unexpected association was found showing that deficits in abstract problem solving may ultimately lead to avoidance of social interactions. 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Appendix A A heat map generated from two-way cluster analysis. Schizotypal Clusters: Low schizotypy is represented in Green, High Positive schizotypy represented in Yellow, while High Positive/Negative schizotypy represented in Red. SPQ Factors (from Left to Right column): Referential Thinking, Anxiety, Social Interaction Deficit, and Undetermined. 95 8.2. Appendix B Items of Schizotypal Personality Questionnaire (SPQ) in new factors New Factors No. Item Referential 1 Do you sometimes feel that things you see on the Thinking TV or read in the newspaper have a special meaning to you? 12 Do you believe in telepathy (mind-reading)? 15 I prefer to keep to myself 16 I sometimes jump quickly from one topic to another when speaking 19 Do some people drop hints about you or say things with a double meaning? 21 Are you sometimes sure that other people can tell that you are thinking? 25 I sometimes forget what I am trying to say 27 Do you sometimes get concerned that friends or coworkers are not really loyal or trustworthy? 30 Do you believe in clairvoyancy (psychic forces, fortune telling)? 52 Have you found that it is best not to let other people know too much about you? 73 I tend to keep my feeling to myself Anxiety 17 24 29 33 38 46 54 57 66 68 71 I am poor at expressing my true feelings by the way I talk and look I am mostly quiet when with other people I get anxious when meeting people for the first time I find it hard to be emotionally close to other people Do you often feel nervous when you are in a group of unfamiliar people? I feel very uncomfortable in social situations involving unfamiliar people I would feel very anxious if I had to give speech in front of a large group of people I tend to keep in the background on social occasions Do you feel that you are unable to get “close” to people? I do not have an expressive and lively way of speaking I feel very uneasy talking to people I do not know well Α .73 .84 96 Social Interaction Deficit 3 7 8 9 10 13 14 23 28 34 37 45 49 50 53 58 60 63 Undetermined 2 4 5 6 11 18 20 Have you had experiences with the supernatural People sometimes find it hard to understand what I am saying People sometimes find me aloof and distant I am sure I am being talked about behind my back I am aware that people notice me when I go out for a meal or to see a film Have you ever had the sense that some person or force is around you, even though you cannot see anyone? People sometimes comment on my unusual mannerisms and habits Sometimes other people think that I am a little strange Have you ever notice a common event or object that seemed to be a special sign for you? I often ramble on too much when speaking Do you sometimes see special meanings in advertisements, shop windows, or in the way things are arranged around you? When shopping, do you get the feeling that other people are taking notice of you? Writing letters to friends is more trouble than it is worth I sometimes use words in unusual ways When you see people talking to each other, do you often wonder if they are talking about you? Do you tend to wander off the topic when having a conversation Do you sometimes feel that other people are watching you? Do you sometimes feel that people are talking about you? .81 I sometimes avoid going to places where there will be many people because I will get anxious Have you often mistaken objects or shadows for people, or noises for voices? Other people see me as slightly eccentric (odd) I have little interest in getting to know other people I get very nervous when I have to make polite conversation Do you often feel that other people have got it in for you? Do you ever get nervous when someone is walking .88 97 22 26 31 32 35 36 39 40 41 42 43 44 47 48 51 55 56 59 61 62 64 65 67 69 70 72 behind you? When you look at a person, or yourself in a mirror, have you ever seen the face change right before your eyes? I rarely laugh and smile I often hear a voice speaking my thoughts aloud Some people think that I am a very bizarre person My “non-verbal” communication (smiling and nodding during a Y/N conversation) is poor I feel I have to be on my guard even with friends Can other people feel your feelings when they are not there? Have you ever seen things invisible to other people? Do you feel that there is no-one you are really close to outside of your immediate family, or people you can confide in or talk to about personal problems? Some people find me a bit vague and elusive during a conversation I am poor at returning social courtesies and gestures Do you often pick up hidden threats or put-downs from what people say or do? Have you had experiences with astrology, seeing the future, UFOs, ESP or a sixth sense? Do everyday things seem unusually large or small? I tend to avoid eye contact when conversing with others Have you ever felt that you are communicating with another person telepathically (by mindreading)? Does your sense of smell sometimes become unusually strong? I often feel that other have it in for me Do you ever suddenly feel distracted by distant sounds that you are not normally aware of? I attach little importance to having close friends Are your thoughts sometimes so strong that you can almost hear them? Do you often have to keep an eye out to stop people from taking advantage of you? I am an odd, unusual person I find it hard to communicate clearly what I want to say to people I have some eccentric (odd) habits People occasionally comment that my conversation 98 74 is confusing People sometimes stare at me because of my odd appearance [...]... schizotypal clusters may be hypothesized The clusters are namely; low schizotypy, high positive schizotypy, high negative schizotypy, and high positive and negative schizotypy Secondly, to attain in- depth understanding on how different profiles of schizotypy may affect functioning and behaviors, an array of neurocognitive tasks and measures of non-schizotypal personality traits are included in this study... discovery of associations between schizotypy and neurocognition and personality traits may help resolve current conflicting findings We expect participants scoring high on several schizotypy dimensions to perform worse on the tasks and also to feel more anxious and depressed Thirdly, we also expect deficits in executive functioning, sustained attention and memory to be apparent in the high schizotypy. .. studies only investigate schizotypy as a whole construct without in- depth examination of individual schizotypy dimensions and their association with specific neurocognitive deficits and personality traits Thirdly, there is also a lack of knowledge on non-schizotypal personality traits affecting schizotypy Lastly, though several cognitive impairments were found present in both schizotypy and schizophrenia,... only negative schizotypy was found associated with high levels of anxiety (Braunstein-Bercovitz, 2000) To the best of our knowledge, no study has yet found an association between personality traits and disorganized features of schizotypy In conclusion, non-schizotypal personality traits are also important in developing an understanding of the continuation of schizotypy to schizophrenia and other schizophrenia-spectrum... of personality traits on schizotypy, present findings are still conflicting and insubstantial For instance, Lewandowski et al (2006) found anxiety and depression to be more related to positive than negative schizotypy, yet another study found positive schizotypy associated with anxiety and depression while negative schizotypy was only associated with depression (Mohanty et al., 2008) On the other hand,... observed in the general population and findings are more generalizable as compared to findings from student samples Hence research samples taken from the non-clinical general population are much superior to student samples A final advantage of using psychometrically defined schizotypes is the ability to obtain information that are useful for early detection of „high-risk‟ individuals developing psychosis and. .. clinically assessed schizophrenia is more consistently found (Chen, Hsiao, & Lin, 1997; Raine, 2006; Raine et al., 1994; Vollema & van den Bosch, 1995) The additional factor is formed by the splitting of the positive features into two separate factors as defined by delusions and hallucinations, and bizarre thoughts and behaviors respectively In the study by Raine and colleagues (1994), five competing... neurocognition and personality traits by correlating the individual schizotypy cluster with neurocognitive functions and measures of personality traits and emotional states Thirdly, this study also aims to determine potential endophenotypes that are shared between schizotypy and schizophrenia, so as to uncover possible etiological factors of schizophrenia and other schizophrenia spectrum disorders via the investigation... investigation of schizotypy Hence, the present study will investigate schizotypy in an Asian population, specifically in healthy English speaking Singaporean Chinese Due to 24 possible cultural differences in the expression of schizophreniform behaviors, the factor structure of schizotypy in this Asian population will first be determined According to limited literature relating to cluster analysis (Loughland &... cultural and ethnic differences, schizotypy may or may not be affected differently In a study by Guo and colleagues (2011), a gender effect in schizotypy was investigated in a Chinese population In line with previous Western studies, gender differences were found related to negative schizotypal personality traits, namely no close friends and constricted affect In contrast, no gender difference was found in