Psychlopedia -- Key concepts -- Psychological disorders and difficulties -- Schizotypy
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Some individuals can exhibit symptoms that resemble schizophrenia, but are not actually afflicted with this disorder. For example, they might experience unusual sensations, such as loud thoughts in their head, a deluge of ideas, or a feeling they have developed magical powers. In addition, they might experience disturbances in their thoughts, such as an inability to concentrate or muddled speech. Furthermore, they might demonstrate aloof behaviour, in which they maintain a distance between themselves and other individuals and do not enjoy many activities. Finally, they might behave impulsively, such as disregard instructions, smash objects, or consume too much food. These manifestations are often referred to as manifestations of a latent personality construct called schizotypy (for a detailed analysis of issues that relate to schizotypy, see Lenzenweger, 2010).
Lenzenweger (2010) offers some intriguing case studies of individuals who manifest elevated levels of schizotypy, but not schizophrenia. One of the case studies revolved around a physics student, who is usually isolated from his peers. He does occasionally speak to someone, but only briefly, usually without listening. He also uses words, like technicalizing, that he has essentially contrived. He maintains that he experiences no strong emotions, apart from anxiety when he is near any other people, except his parents. Occasionally, his perception of his body is distorted: He might momentarily perceive his hand as very large, although he does not actually believe the size of this appendage has changed.
The second case study revolved around an older postal worker. Apart from greetings, he seldom converses with one anyone, humming to himself while he works. He often sleeps on the couch, despite owning a bed. He sometimes notices trails of colors following stars, a pattern he feels is significant for him. He usually shuns banks, concerned they monitor him too closely--but did visit a bank to complain about the updated design of the $20 note (Lenzenweger, 2010).
The third case study was about a woman with a degree, but only a clerical job. At work, she often daydreams about an aspiration. She feels very uneasy interacting with other people. She sometimes feels confused, even when she completes simple tasks. She does sometimes perceive specific numbers as magical. She notices the expressions and mannerisms of other people, sometimes interpreting even a smile as an indication the person knows something private about her. She reads philosophy and religious texts, but has not dated anyone.
Definitions and distinctions
Individuals who manifest elevated levels of schizotypy demonstrate several features, as delineated by Lenzenweger (2010). First, they have usually developed few, if any, friends apart from family. Second, their language or speech is often idiosyncratic and, therefore, difficult to understand. Third, they might experience distorted perceptions, such as body parts as misshapen. Fourth, they often perceive ordinary events, like the arrangements in the window of a retail shop, as significant to them in some sense. They might, for example, feel that a speech on TV is directed to them. Fifth, they might feel a sense of magic, such as believe they can control some remote event. Sixth, their facial expressions often seem devoid of emotion, although often feel very anxious in social settings, even experiencing grave suspicion.
Despite these signs and symptoms, they do not experience the hallucinations, delusions, or thought disorder that characterizes schizophrenia. Although they might experience some unusual sensations, such as the feeling they are being monitored or cheated, they do not actually believe these thoughts (Lenzenweger, 2010).
Lenzenweger (2010) clarifies the distinction between schizotypy and schizophrenia. According to Lenzenweger (2010), schizoptypy is a latent personality construct rather than a description of overt behaviors. Schizotypy can range from low--or normal--to pathological.
Elevated levels of schizoptypy increase the likelihood of an illness called schizophrenia. Thus, schizoptypy can be regarded as a liability for schizophrenia. Thus, elevated levels of schizotypy might represent a vulnerability to psychosis (e.g., Eckblad & Chapman, 1983; Kaczorowski, Barrantes-Vidal, & Kwapil, 2009; Keshavan, Diwadkar, Montrose, Rajarethinam, & Sweeney, 2005). Schizophrenia may significantly precede the clinical manifestations of schizophrenia.
This liability of schizophrenia--that is, elevated levels of schizotypy--can manifest as other symptoms, called schizotypic psychopathology. That is, schizotypic psychopathology represents an alternative manifestation of these elevated levels of schizotypy rather than merely a milder or prodromal form of schizophrenia (Lenzenweger, 2010). According to Lenzenweger (2010), an examination of schizotypic psychopathology enables researchers to study this liability for schizophrenia--including genetic, biological, social, and contextual determinants--without confounds such as medication and institutionalization.
Evolution of schizotypy
Several psychologists, during the 1960s, 1970s, and 1980s, assumed that some features, characteristic of schizophrenia, might be underpinned by cardinal personality traits. For example, the model developed by Eysenck assumed that personality can be represented by three continuous traits: extraversion, neuroticism, and psychoticism. In this scheme, high levels of psychoticism correspond to features that characterize schizophrenia (Eysenck & Eysenck, 1975).
Claridge coined the term schizotypy to represent the unusual behaviors and experiences of individuals in the general population (see also Claridge, McCreery, Mason, Bentall, Boyle, Slade, & Popplewell, 1996). This research highlighted that schizotypy entails several distinct clusters of behavior or experience. In particular, some individuals might report unusual experiences or thoughts-hallucinations, magical beliefs, intense superstitions, or delusional interpretations. Second, other individuals might exhibit disordered cognition, such as tangential or extraneous thoughts. Third, individuals might report social anhedonia, which represents an ability to derive enjoyment from social or physical stimulation. Fourth, some individuals show impulsive and deviant behavior, violating social conventions and prescribed rules.
Schizotypy and social behaviour
Schizotypy is associated with limited eye contact, deficient social skills, hostility, odd behavior, and social withdrawal (see Keltner & Kring, 1998; Zborowski & Garske, 1993). More specifically, ambiguous or novel social settings, such as attending a party alone rather than visiting a relative, are especially aversive to individuals who exhibit elevated levels of schizotypic features (Quirk, Subramanian, & Hoerger, 2007).
These findings are consistent with the proposition that social withdrawal might represent a repercussion of cognitive deficits. In particular, social interactions demands complex cognitive operations, such as anticipating the behavior of someone else, searching memory for behavioral repertoires, and predicting the impact of specific behaviors. These operations are especially significant when the social context is ambiguous or novel, because individuals cannot merely invoked automatic and practiced routines. Schizotypy is associated with deficits in attention, working memory, and other cognitive domains (e.g., Barch, Mitropoulou, Harvey, New, Silverman, & Siever, 2004). Hence, individuals who exhibit these features might operate unsuccessfully in these ambiguous environments. Accordingly, these individuals might feel especially uneasy in these ambiguous contexts.
Schizotypy and cognition
Attention, working memory, and executive functions
Schizotypy may represent deficits in executive functioning, which entails the psychological processes that supersede habitual, but unsuitable, inclinations with novel responses and behaviors to to fulfill important goals. In particular, when schizotypy is elevated, response inhibition may be impaired (Unsworth, Miller, Lakey, Young, Meeks, Campbell, & Goodie, 2009). That is, participants are not as able to suppress habitual responses, such as saccades to conspicuous, but uninformative, cues.
Similarly, negative priming is also deficient in participants who report many features of schizotypy (Beech & Claridge, 1987). That is, unlike other participants, these individuals do not respond appreciably more slowly to a stimulus that had been irrelevant, and thus inhibited, in a previous trial.
Furthermore, elevated levels of schizotypy coincide with limited fluency (Unsworth, Miller, Lakey, Young, Meeks, Campbell, & Goodie, 2009). That is, individuals who demonstrate schizotypy cannot generate many instances of categories, such as names of animals.
Many studies have also shown that individuals who exhibit schizotypal features demonstrate deficits in attention and working memory (e.g., Barch, Mitropoulou, Harvey, New, Silverman, & Siever, 2004). For example, sustained attention is deficient in individuals who report schizotypal features (Bergida &Lenzenweger, 2006).
Differentiating figure and ground
Some facets of schizotypy correspond to an inability to differentiate figure and ground. To assess this capacity, individuals need to locate a specific pattern from a complex array of overlapping shapes and objects. Individuals who demonstrate aloof behaviour cannot identify these figures proficiently. Conceivably, these individuals are unable to thoughts, such as images of a holiday, to motivate or guide their behaviour. This inability to guide their behaviour through images might compromise their capacity to extract figures from the background.
In contrast, individuals who behave impulsively perform proficiently on this task, often outperforming participants who did not exhibit schizotypy. These individuals rapidly shift attention from one object to the next, which could facilitate their performance on this task.
Some facets of schizotypy, especially unusual experiences and cognitive disorganization, seemed to be positively related to creativity and academic achievement (Nettle, 2006). This finding implies that schizotypy can, in some contexts, be adaptive.
Measures of schizotypal personality features are indeed related to deficits in eye tracking (see Keefe, Silverman, Mohs, Siever, Harvey, Friedman, et al., 1997; Lencz, Raine, Scerbo, Redmon, Brodish, Holt, & Bird, 1993), even after controlling age, sex, and intellectual level. In particular, three facets of schizotypy-disorganization, reality distortion, and negative features, as measured by the Schizotypal Personality Questionnaire (Raine, 1991)--was related to diminished gain, which is the ratio of eye velocity over target velocity.
Furthermore, rate of catch-up saccades was positively associated with disorganization. Catch up saccades represent saccades in the same direction as the target, preceded and followed by pursuit, with a maximum amplitude of 5 degrees. These findings align with the results observed by Friedman, Jesberger, Siever, Thompson, Mohs, and Meltzer (1995), which revealed that rate of catch-up saccades was also elevated in patients diagnosed with schizophrenia.
Possible causes of schizotypy
Some scholars assume that social anhedonia--the inability to derive pleasure from social interactions, a common manifestation of schizotypy--might be related to abnormality in the dopaminergic system of the brain, implicated in human rewards. That is, this abnormality might correspond to limitations in experiencing pleasure in rewarding contexts.
When individuals show the positive indicators of schizotypy, like beliefs that mirror delusions or experiences that resemble hallucinations, they often show elevated activation of the right, rather than left, hemisphere of the brain, at least in some tasks (Grimshaw, Bryson, Atchley, & Humphrey, 2010). To illustrate, in most of the population, when the meaning of a stimulus is ambiguous, after sufficient time, the left hemisphere usually primes the dominant meaning and inhibits peripheral meanings. In contrast, the right hemisphere primes both dominant and peripheral meanings. In a study conducted by Grimshaw, Bryson, Atchley, and Humphrey (2010), when the participants reported schizotypy, peripheral meanings were less likely to be inhibited.
Similarly, many other tasks indicate this form of schizotypy coincides with a bias towards the right hemisphere or left visual space. Individuals who exhibit these positive symptoms often bisect lines towards the left (Brugger & Graves, 1997; for similar tasks, see Luh & Gooding, 1999).
Schizotypy might be associated with limitations in inhibition. For example, studies indicate that negative priming is deficient in participants who report many features of schizotypy (Beech & Claridge, 1987). Negative priming represents the tendency to respond more slowly to a stimulus that had been irrelevant, and hence inhibited, in a previous trial. Accordingly, individuals who report schizotypic features might not inhibit distracting information effectively.
Dissociation of arousal systems
The correlation between various psychophysiological indicators, such as cortical and autonomic arousal, has been shown to be abnormal in individuals who report schizotypy (Claridge, 1967; Claridge & Clark, 1982). Likewise, in a study conducted by McCreery and Claridge (1996), attempted to induce a hallucinatory episode in the laboratory. This procedure induced elevated activation of the right hemisphere, but only in individuals who report schizotypic features.
Potentially, schizotypy might represent hyperarousal, perhaps because of deficient homoestasis in the central nervous system. Micro-sleeps, intrusions of Stage 1 sleep while awake, are sometimes a reaction to extreme stress and hyperarousal. That is, to maintain homeostasis, elevated levels of stress can sometimes evoke sleep (e.g., Oswald, 1962). These micro-sleeps could potentially explain the phenomenological similarities between psychosis and Stage 1 sleep: hallucinations and unusual affective responses, for example (see McCreery, 1997; see also Claridge, McCreery, Mason, Bentall, Boyle, Slade, & Popplewell, 1996).
Some evidence of this proposition has accumulated. Heightened arousal, as gauged by self report, correlates with the experience of hallucinations and other perceptual anomalies (Claridge, McCreery, Mason, Bentall, Boyle, Slade, & Popplewell, 1996).
This proposition that schizotypy might represent a response to heightened arousal can explain some anomalies discovered in patients diagnosed with schizophrenia--arguably the clinical manifestation of elevated schizotypy. To illustrate, when administered with sedative drugs, patients who exhibit catatonic sometimes emerge from this state (Stevens & Darbyshire, 1958). These sedative drugs might alleviate arousal and thus curb the responses to heightened stress.
Only a limited set of studies has examined the social antecedents to schizotypy. Many studies, however, have explored the social antecedents to schizophrenia, some of which are likely to affect schizotypy as well.
Adversities in social contexts tend to coincide with schizophrenia. These adversities might include social exclusion, socioeconomic deprivation, and frequent migration (e.g., Mueser & McGurk 2004; Wicks, Hjern, Gunnell, Lewis, & Dalman, 2005), all of which can undermine the formation of social bonds and promote family dysfunction. Similarly, childhood abuse and trauma also predict subsequent schizophrenia (e.g., Schenkel, Spaulding, DiLillo, &Silverstein, 2005).
Disturbed sense of of self
Sass and Parnas (2003) ascribe schizophrenia, as well as the precursors of schizophrenia, to a disturbance in a concept called ipseity. This theory could arguably explain schizotypy as well. When ipseity is disturbed, individuals observe private experiences--their thoughts, sensations, emotions or actions--as objective events, as if perceiving these experiences from the perspective of someone else.
To clarify, most individuals can decipher which of their thoughts or actions are connected to the self. If they choose to raise their arm, they tacitly know they are responsible for this action. If someone else lifts their arm, they tacitly know they are not responsible for this action. If they speak with their eyes closed, they know the thoughts they express are their own. If they are mimicked by someone else while their eyes are closed, they know they did not express these thoughts. In short, individuals experience a tacit sense of self--a sense that differentiates their own cognitions and actions from the thoughts and behaviors of other people.
In addition to this tacit sense of self, individuals can also perceive themselves objectively. They can evaluate their features or behaviors from the perspective of someone else. They can appraise themselves as if they were evaluating an object. That is, they can objectify themselves. When ipseity is intact, although they can objectify themselves, they also experience this tacit sense of self, almost continuously. When ipseity is disturbed, individuals ted to objectify themselves; their tacit sense of self is disrupted.
If ipseity is disrupted, three properties tend to emerge. First, individuals experience hyper-reflexivity. They direct their attention, almost excessively, to private experiences, such as thoughts or sensations, but from an objective perspective.
To illustrate the cause of hyper-reflexivity, because ipseity is disturbed, individuals cannot as readily distinguish events that are connected to the tacit self--their thoughts, emotions, bodily sensations, and so forth--from events that are connected to other people or agents. For example, when most individuals emit a smell, such as the whiff of cologne, they do not unduly direct their attention to this odor. They recognize this odor is just a part of themselves. When these individuals recognize the same smell, but know this odor is not emitted from the self, they will direct their attention to the source. This odor, after all, might be emanating from a threat, like a potential burglar. When ipseity is disrupted, however, individuals do not as readily perceive themselves as the source of some smell. They direct their attention to this smell, vigilantly and disproportionately. Similarly, they direct their attention to other sensations, thoughts, or events that most individuals recognize are merely connected to themselves.
Second, these individuals exhibit diminished self-affection. They do not experience a subjective sense of vitality or intensity. They do not perceive themselves as present or instrumental.
To clarify, most individuals tacitly recognize their motivations, wishes, and desires are connected to their tacit self. They feel their motivation to meet someone, for example, is their own. When ipseity is disturbed, however, individuals do not recognize these motivations, wishes, or desires are their own. These goals are not branded with a sense of self. These goals feel more like objective concepts, wafting in their air, rather than motivational forces. Consequently, these individuals do not experience a sense of vitality. Their actions are not underpinned by a cohesive set of motivations.
Third, individuals experience a disturbed hold. That is, objects do not seem to cohere to a unified framework. Many objects or thoughts seem to appear or vanish haphazardly.
Specifically, most individuals experience a coherent set of goals and motivations. Objects or thoughts that are germane to these goals or motivations are salient; other objects or thoughts are not as conspicuous. In contrast, if ipseity is disturbed, this coherence is compromised. The salience of objects and thoughts will depend on more erratic factors rather than enduring motivations or cognitions.
To illustrate these properties, for some individuals, the experience of music diminishes. Rather than merely experience the vitality and intensity of the music experience, some individuals become more aware of their reflections and thoughts about the music. They feel they are observing their reflections instead of experiencing the music itself. This example corresponds to hyper-reflexivity towards thoughts, a decline in vitality, and the inability to unify these sensations to a unified framework. Similarly, before patients are diagnosed with schizophrenia, they often express complaints that epitomize this disturbed ipseity. They might contend "I feel I have lost contact with myself" or "Something inside me turned non-human". They might also feel "I have become a spectator to my own life" or "half-awake".
According to Sass and Parnas (2003), these features of a disturbed ipseity--a disturbed sense of self--underpins the putative positive symptoms, negative symptoms, and thought disturbances that characterize schizophrenia. For example, these individuals do not recognize some of their thoughts or sensations as their own. These thoughts and sensations might seem to emanate from other sources, culminating in hallucinations.
Disturbed ipseity can also explain negative symptoms. As Sass and Parnas (2003) underscore, negative symptoms, despite their name, do not represent the absence of experience. Even flattened affect, for example, is usually associated with strong physiological reactions, epitomizing a raft of disorganized private experiences. Undue attention to trivial objects and events, reflecting hyper-reflexivity and a disturbed hold, generate an erratic sense of awareness, often manifesting as apathy.
This characterization can also explain the thought disorders that characterize schizophrenia. Individuals often feel they experience an infinite number of unfamiliar impressions and sensations, ultimately manifesting as erratic thoughts and comments. This experience can be explained by hyper-reflexivity to sensations to which most individuals do not attend. Similarly, this experience indicates disturbed grip--the absence of a unified and coherent set of motivations, increasing the salience of extraneous events.
Measurement of schizotypy
The Schizotypal Personality Questionnaire
Raine (1991) developed the Schizotypal Personality Questionnaire, or SPQ, to characterize the extent to which individuals manifest features of schizotypal personality. This questionnaire, the most prevalent measure of schizotypy in the research domain (Wuthrich & Bates, 2006), comprises 74 items that assess cognitive, perceptual, affective, and interpersonal features, corresponding to the symptoms stipulated by the DSM-III-R. Participants specify whether or not they feel or believe they exhibit these features.
The SPQ comprises nine subscales--one corresponding to each of the nine criteria for schizotypal personality disorder, as delineated by the DSM-III-R. These nine subscales can be combined to form three broader scales: reality distortion, disorganization, and negative symptom components in schizophrenia (Lenzenweger & Dworkin, 1996; Raine, Reynolds, Lenez, Scerbo, Triphon, & Kim, 1994). Cronbach's alpha for these scales, on average, approximates .74 (Raine, 1991). Test-retest reliability is also high across a two month interval (r = .82, Raine, 1991).
Kaczorowski, Barrantes-Vidal, and Kwapil (2009) also accumulated evidence to distinguish between the positive and negative manifestations of schizotypy. Positive schizotypy was correlated with impairments in sensory integration. In contrast, negative schizotypy was correlated with impairments in motor coordination and motor sequencing--which may represent dysfunction in a circuit that connects the prefrontal cortex, thalamus, and cerebellum--as well as deficits in eye movement and memory recall. Hence, these distinct forms of schizotypy seem to coincide with different neurological impairments.
Extensions to the Schizotypal Personality Questionnaire
Chmielewski and Watson (2008) challenged this factor structure. They administered the SPQ to 556 students, twice over a two week interval. When the responses to the 74 items were subjected to a factor analysis, five dimensions were unearthed. These dimensions included social anhedonia, unusual beliefs and experiences, social anxiety, mistrust, and eccentricity or oddity--and were stable across time.
In this context, social anhedonia primarily represents the absence of close friends as well as restricted range of affect. Unusual beliefs and experiences refer to magical thinking and unusual perceptual experiences. Mistrust relates to suspicious thoughts and behavior. Eccentricity and oddity includes both odd behavior and odd speech.
Furthermore, social anxiety was inversely related to extraversion and positively related to neuroticism; otherwise, the five dimensions were only modestly related to personality (Chmielewski & Watson, 2008). All of the scales were positively related to measures of dissociation, but these correlations were lower for social anhedonia and social anxiety. More importantly, these five dimensions were only weakly correlated with each other, highlighting the multifaceted nature of schizotypy.
Barch, D. M., Mitropoulou, V., Harvey, P. D., New, A. S., Silverman, J. M., & Siever, L. J. (2004). Context-processing deficits in schizotypal personality disorder. Journal of Abnormal Psychology, 113, 556-568.
Beech, A.R. and Claridge, G.S. (1987). Individual differences in negative priming: Relations with schizotypal personality traits. British Journal of Clinical Psychology, 78, 349-356.
Bergida, H., &Lenzenweger, M. F. (2006). Schizotypy and sustained attention: Confirming evidence from an adult community sample. Journal of Abnormal Psychology, 115, 545-551.
Braunstein-Bercovitz, H., Rammsayer, T., Gibbons, H., & Lubow, R. E. (2002). Latent inhibition deficits in high-schizotypal normals: Symptom-specific or anxiety-related? Schizophrenia Research, 53, 109-121.
Brod, J. H. (1997). Creativity and schizotypy. In G. Claridge (Ed.), Schizotypy: Implications for illness and health (pp. 274-298). New York: Oxford University Press.
Broks, P. (1984). Schizotypy and hemisphere function: II. Performance asymmetry on a verbal divided visual-field task. Personality and Individual Differences, 5, 649-656.
Brugger, P., & Graves, R. E. (1997). Right hemispatial inattention and magical ideation. European Archives of Psychiatry and Clinical Neuroscience, 247, 55-57
Burch, G. S. J., Pavelis, C., Hemsley, D. R., & Corr, P. J. (2006). Schizotypy and creativity in visual artists. British Journal of Psychology, 97, 177-190.
Cantor-Graae, E., & Selten, J. P. (2005). Schizophrenia and migration: a meta-analysis and review. American Journal of Psychiatry, 162, 12-24.
Chmielewski, M., & Watson, D. (2008). The heterogeneous structure of schizotypal personality disorder: Item-level factors of the schizotypal personality questionnaire and their associations with obsessive-compulsive disorder symptoms, dissociative tendencies, and normal personality. Journal of Abnormal Psychology, 117, 364-376.
Cimino, M., & Haywood, M. (2008). Inhibition and facilitation in schizotypy. Journal of Clinical and Experimental Neuropsychology, 30, 1-12.
Claridge, G.. (1967). Personality and Arousal. Oxford: Pergamon.
Claridge, G. (1997). Schizotypy: Implications for illness and health. New York: Oxford University Press.
Claridge, G. S. and Clark, K. H. (1982). Covariation between two flash threshold and skin conductance level in first breakdown schizophrenics: Relationships in drug free patients and effects of treatment. Psychiatry Research, 6, 371 380.
Claridge, G., McCreery, C., Mason, O., Bentall, R., Boyle, G., Slade, P., & Popplewell, D. (1996). The factor structure of 'schizotypal' traits: A large replication study. British Journal of Clinical Psychology, 35, 103-115.
Eckblad, M., & Chapman, L. J. (1983). Magical ideation as an indicator of schizotypy. Journal of Consulting and Clinical Psychology, 51, 215-225.
Eysenck, H. J., & Eysenck, S. B. G. (1975). Manual of the Eysenck Personality Questionnaire. London: Hodder and Stoughton.
Fisher, J. E., Mohanty, A., Herrington, J. D., Koven, N. S., Miller, G. A., & Heller, W. (2004). Neuropsychological evidence for dimensional schizotypy: Implications for creativity and psychopathology. Journal of Research in Personality, 38, 24-31.
Friedman, L., Jesberger, J. A., Siever, L. J., Thompson, P., Mohs, R., & Meltzer, H. Y. (1995). Smooth pursuit in patients with affective disorders or schizophrenia: Analysis with specific oculomotor measures, RMS error and qualitative ratings. Psychological Medicine, 25, 387-403.
Gooding, D. C., Matts, C. W., & Rollmann, E. A. (2006). Sustained attention deficits in relation to psychometrically identified schizotypy: Evaluating a potential endophenotypic marker. Schizophrenia Research, 82, 27-37.
Gray, N. S., Fernandez, M., Williams, J., Ruddle, R. A., & Snowden, R. J. (2002). Which schizotypal dimensions abolish latent inhibition? British Journal of Clinical Psychology, 41, 271-284.
Grimshaw, G. M., Bryson, F. M., Atchley, R. A., & Humphrey, M. K. (2010). Semantic ambiguity resolution in positive schizotypy: a right hemisphere interpretation. Neuropsychology, 24, 130-138.
Grove, W. M., Lebow, B. S., Clementz, B. A., Cerri, A., Medus, C., & Iacono, W. G. (1991). Familial prevalence and coaggregation of schizotypy indicators: A multitrait family study. Journal of Abnormal Psychology, 100, 115-121.
Hori, H., Nagamine, M., Soshi, T., Okabe, S., Kim, Y., & Kunugi, H. (2008). Schizotypal traits in healthy women predict prefrontal activation patterns during a verbal fluency task: A near-infrared spectroscopy study. Neuropsychobiology, 57, 61-69.
Hori, H., Ozeki, Y., Terada, S., & Kunugi, H. (2008). Functional near-infrared spectroscopy reveals altered hemispheric laterality in relation to schizotypy during verbal fluency task. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 32, 1944-1951.
Kaczorowski, J. A., Barrantes-Vidal, N., &; Kwapil, T. R. (2009). Neurological soft signs in psychometrically identified schizotypy. Schizophrenia Research, 115, 293-302.
Keefe, R. S. E., Silverman, J. M., Mohs, R. C., Siever, L. J., Harvey, P. D., Friedman, L., et al. (1997). Eye tracking, attention, and schizotypal symptoms in nonpsychotic relatives of patients with schizophrenia. Archives of General Psychiatry, 54, 169-176.
Kelley, M. P., & Bakan, P. (1999). Eye tracking in normals: SPEM asymmetries and association with schizotypy. International Journal of Neuroscience, 98, 27-81.
Keltner, D., & Kring, A. M. (1998). Emotion, social function, and psychopathology. Review of General Psychology, 2, 320-342.
Kendler, K. S., Ochs, A. L., Gorman, A. M., Hewitt, J. K., Ross, D. E., & Mirsky, A. F. (1991). The structure of schizotypy: A pilot multitrait twin study. Psychiatry Research, 36, 19-36.
Kerns, J. (2005). Positive schizotypy and emotional processing. Journal of Abnormal Psychology, 114, 392-401.
Keshavan, M. S., Diwadkar, V. A., Montrose, D. M., Rajarethinam, R., & Sweeney, J. A. (2005). Premorbid indicators and risk for schizophrenia: A selective review and update. Schizophrenia Research, 79, 45-57.
Korfine, L., & Lenzenweger, M. F. (1995). The taxonicity of schizotypy: A replication. Journal of Abnormal Psychology, 104, 26-31.
Kremen, W. S., Faraone, S. V., Toomey, R., Seidman, L., & Tsuang, M. (1998). Sex differences in self-reported schizotypal traits in relatives of schizophrenic probands. Schizophrenia Research, 34, 27-37.
Lencz, T., Raine, A., Scerbo, A., Redmon, M., Brodish, S., Holt, L., & Bird, L. (1993). Impaired eye tracking in undergraduates with schizotypal personality disorder. American Journal of Psychiatry, 150, 152-154.
Lenzenweger, M. (1998). Schizotypy and schizotypic psychopathology: Mapping an alternative expression of schizophrenia liability. In M. Lenzenweger & R. Dworkin (Eds.), Origins and development of schizophrenia: Advances in experimental psychopathology (pp. 93-122). Washington, DC: American Psychological Association.
Lenzenweger, M. F. (2010). Schizotypy and schizophrenia: The view from experimental psychopathology. New York: Guilford Press.
Lenzenweger, M. F., & Dworkin, R. H. (1996). The dimensions of schizophrenia phenomenology? Not one or not two, at least three, perhaps four. British Journal of Psychiatry, 168, 432-440.
Lenzenweger, M. F., & Korfine, L. (1992). Confirming the latent structure and base rate of schizotypy: A taxometric analysis. Journal of Abnormal Psychology, 101, 567-571.
Lenzenweger, M. F., & O'Driscoll, G. A. (2006). Smooth pursuit eye movement and schizotypy in the community. Journal of Abnormal Psychology, 115, 779-786.
Lubow, R. E., Kaplan, O., & De la Casa, G. (2001). Performance on the visual search analog of latent inhibition is modulated by an interaction between schizotypy and gender. Schizophrenia Research, 52, 275-287.
Luh, K. E., & Gooding, D. C. (1999). Perceptual biases in psychosis-prone individuals. Journal of Abnormal Psychology, 108, 283-289.
Mason, O., & Claridge, G. (1999). Individual differences in schizotypy and reduced asymmetry using the chimeric faces task. Cognitive Neuropsychiatry, 4, 289-301.
McCreery, C. (1997). Hallucinations and arousability: Pointers to a theory of psychosis. In G. Claridge (Ed.) Schizotypy, Implications for Illness and Health. Oxford: Oxford University Press.
McCreery, C., and Claridge, G. (1996). A study of hallucination in normal subjects - II. Electrophysiological data. Personality and Individual Differences, 21, 749-758.
McCreery, C., & Claridge, G. (2002). Healthy schizotypy: The case of out-of-the-body experiences. Personality and Individual Differences, 32, 141-154.
Meehl, P.E. (1962). Schizotaxia, schizotypy, schizophrenia. American Psychologist, 17, 827 838.
Miller, G. F., & Tal, I. R. (2007). Schizotypy versus openness and intelligence as predictors of creativity. Schizophrenia Research, 93, 317-324.
Mohr, C., Krummenacher, P., Landis, T., Sandor, P. S., Fathi, M., & Brugger, P. (2005). Psychometric schizotypy modulates levodopa effects on lateralized lexical decision performance. Journal of Psychiatric Research, 39, 241-250.
Morgan, C., Bedford, N., & Rossell, S. L. (2006). Evidence of semantic disorganisation using semantic priming in individuals with high schizotypy. Schizophrenia Research, 84, 272-280.
Moritz, S., Andresen, B., Probsthein, E., Martin, T., Domin, F., Kretschmer, G., et al. (2000). Stimulus onset asynchronicity as a modulator of negative priming in schizotypy. Personality and Individual Differences, 29, 649-657.
Moritz, S., & Mass, R. (1997). Reduced cognitive inhibition in schizotypy. British Journal of Clinical Psychology, 36, 365-376.
Mueser, K.T., & McGurk S. R. (2004). Schizophrenia. The Lancet, 363, 2063-2072
Nettle, D. (2006). Schizotypy and mental health amongst poets, visual artist, and mathematicians. Journal of Research in Personality, 40, 876-890.
Oswald, I. (1962). Sleeping and Waking: Physiology and Psychology. Amsterdam: Elsevier.
Quirk, S. W., Subramanian, L., & Hoerger, M. (2007). Effects of situational demand upon social enjoyment and preference in schizotypy. Journal of Abnormal Psychology, 116, 624-631.
Raine, A. (1991). The SPQ: A scale for the assessment of schizotypal personality based on DSM-III-R criteria. Schizophrenia Bulletin, 17, 555-564.
Raine, A., Reynolds, C., Lenez, T., Scerbo, A., Triphon, N., & Kim, D. (1994). Cognitive-perceptual, interpersonal, and disorganized features of schizotypal personality. Schizophrenia Bulletin, 20, 191-201.
Rawlings, D., & Claridge, G. (1984). Schizotypy and hemisphere function: III. Performance asymmetries on tasks of letter recognition and local-global processing. Personality and Individual Differences, 5, 657-663.
Reed, P., Wakefield, D., Harris, J., Parry, J., Cella, M., & Tsakanikos, E. (2008). Seeing non-existent events: Effects of environmental conditions, schizotypal symptoms, and sub-clinical characteristics. Journal of Behavior Therapy and Experimental Psychiatry, 39, 276-291.
Ross, S. R., Lutz, C. J., & Bailley, S. E. (2002). Positive and negative symptoms of schizotypy and the five-factor model: A domain and facet level analysis. Journal of Personality Assessment, 79, 53-72.
Sass, L. A., & Parnas, J. (2003). Schizophrenia, consciousness, and the self. Schizophrenia Bulletin, 29, 427-444.
Schenkel, L. S., Spaulding, W. D., DiLillo, D., & Silverstein, S. M. (2005). Histories of childhood maltreatment in schizophrenia: relationships with premorbid functioning, symptomatology, and cognitive deficits. Schizophrenia Research, 76, 273-286.
Shean, G., & Wais, A. (2000). Interpersonal behavior and schizotypy. Journal of Nervous and Mental Disease, 188, 842-846.
Siever, L. J., Friedman, L., Moskowitz, J., Mitropoulou, V., Keefe, R., Roitman, S. L., et al. (1994). Eye movement impairment and schizotypal psychopathology. American Journal of Psychiatry, 151, 1209-1215.
Stevens, J. M., & Darbyshire, A. J. (1958). Shifts along the alert-repose continuum during remission of catatonic 'stupor' with amobarbitol. Psychosomatic Medicine, 20, 99-107.
Steel, C., Hemsley, D. R., & Pickering, A. D. (2007). Associations between schizotypal personality traits and the facilitation and inhibition of the speed of contextually cued responses. Psychiatry Research, 150, 131-140.
Tsakanikos, E. (2004). Latent inhibition, visual pop-out and schizotypy: Is disruption of latent inhibition due to enhanced stimulus salience? Personality and Individual Differences, 37, 1347-1358.
Tsakanikos, E., & Reed, P. (2003). Visuo-spatial processing and dimensions of schizotypy: Figure-ground segregation as a function of psychotic-like features. Personality and Individual Differences, 35, 703-712.
Unsworth, N., Miller, J. D., Lakey, C. E., Young, D. L., Meeks, J. T., Campbell, W. K., & Goodie, A. S. (2009). Exploring the relations among executive functions, fluid intelligence, and personality. Journal of Individual Differences, 30, 194-200.
Weinstein, S., & Graves, R. E. (2002). Are creativity and schizotypy products of a right hemisphere bias? Brain and Cognition, 49, 138-151.
Wicks, S., Hjern, A., Gunnell, D., Lewis, G., & Dalman, C. (2005). Social adversity in childhood and the risk of developing psychosis: A national cohort study. American Journal of Psychiatry, 162, 1652-1657.
Wuthrich, W. M., & Bates, T. C. (2006). Confirmatory factor analysis of the three-factor structure of the Schizotypal Personality Questionnaire and Chapman schizotypy scales. Journal of Personality Assessment, 87, 292-304.
Zborowski, M. J., & Garske, J. P. (1993). Interpersonal deviance and consequent social impact in hypothetically schizophrenia-prone males. Journal of Abnormal Psychology, 102, 482-489.
Created by Dr Simon Moss on 18/10/2008