Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia are fundamentally different notions of the schizophrenia precursor. Both represent a categorical precursor but differ in the nature of their relationships to schizophrenia. Specifically, schizotypy is dimensional, unchanging despite the presence or remission of schizophrenia. In contrast, schizotaxia is a transitional precursor; the presence of schizophrenia signals the end of schizotaxia. There are also differences in the way in which risk is determined. Schizotypy is reflected in a variety of information processing and experiential aberrations, is typically assessed using self-report measures, and is best identified using taxometric analyses. In contrast, schizotaxia is characterised by negative symptoms of schizophrenia and neurocognitive impairment, can be assessed using standardised clinical measures, and is diagnosed at the individual case level. The aim of Phase 1 of this study was to investigate the manifest structure of Meehl�s schizotypy in a sample of psychiatric patients. The aims of Phase 2 were to determine if schizotypy group membership was associated with poorer functioning and to determine the nature of the relationship between Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia. Participants in Phase 1 were 109 psychiatric patients and all completed a self-report measure of schizotypy, the Thinking and Perceptual Style Questionnaire (TPSQ; Linscott & Knight, 2004). Multivariate taxometric analyses of TPSQ subscales yielded evidence of a manifest group structure within the sample. The prevalence of the latent group, presumed to reflect schizotypy, was estimated to be 32% (SD = 8%), as yielded by MAXCOV analyses. MAXCOV analyses also yielded a mean indicator validity of 1.02; variance of 7; base rate estimates of .08; and a goodness of fit index of .98. MAMBAC analyses yielded a mean base rate of 56% (SD = 18%). Twenty-nine participants from Phase 1 took part in Phase 2. Fourteen were from the schizotypy group (had a p value of .85 or higher of schizotypy group membership) and 15 from the nonschizotypy group (had a p value of .03 or lower of schizotypy group membership). Participants completed tests of attention, verbal memory, and executive functioning. Negative symptoms of schizophrenia were also rated and diagnosis was determined using a diagnostic interview. The schizotypy group was significantly impaired relative to the nonschizotypy group on neuropsychological test scores spanning domains of attention, verbal memory, and executive functioning. A current DSM-IV diagnosis was made for 71% of the schizotypy group and 43% of the nonschizotypy group. Individuals were classified as having met criteria for schizotaxia if they had a negative symptom impairment and a neuropsychological impairment in two domains. A total of 7 people of 29 met criteria for schizotaxia, 6 of these people were from the schizotypy group. There was statistical evidence that Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia are not independent. The proposed precursors for schizophrenia may reflect the same construct, not separate entities. Limitations and implications of these results are considered.

Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia are fundamentally different notions of the schizophrenia precursor. Both represent a categorical precursor but differ in the nature of their relationships to schizophrenia. Specifically, schizotypy is dimensional, unchanging despite the presence or remission of schizophrenia. In contrast, schizotaxia is a transitional precursor; the presence of schizophrenia signals the end of schizotaxia. There are also differences in the way in which risk is determined. Schizotypy is reflected in a variety of information processing and experiential aberrations, is typically assessed using self-report measures, and is best identified using taxometric analyses. In contrast, schizotaxia is characterised by negative symptoms of schizophrenia and neurocognitive impairment, can be assessed using standardised clinical measures, and is diagnosed at the individual case level. The aim of Phase 1 of this study was to investigate the manifest structure of Meehl�s schizotypy in a sample of psychiatric patients. The aims of Phase 2 were to determine if schizotypy group membership was associated with poorer functioning and to determine the nature of the relationship between Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia. Participants in Phase 1 were 109 psychiatric patients and all completed a self-report measure of schizotypy, the Thinking and Perceptual Style Questionnaire (TPSQ; Linscott & Knight, 2004). Multivariate taxometric analyses of TPSQ subscales yielded evidence of a manifest group structure within the sample. The prevalence of the latent group, presumed to reflect schizotypy, was estimated to be 32% (SD = 8%), as yielded by MAXCOV analyses. MAXCOV analyses also yielded a mean indicator validity of 1.02; variance of 7; base rate estimates of .08; and a goodness of fit index of .98. MAMBAC analyses yielded a mean base rate of 56% (SD = 18%). Twenty-nine participants from Phase 1 took part in Phase 2. Fourteen were from the schizotypy group (had a p value of .85 or higher of schizotypy group membership) and 15 from the nonschizotypy group (had a p value of .03 or lower of schizotypy group membership). Participants completed tests of attention, verbal memory, and executive functioning. Negative symptoms of schizophrenia were also rated and diagnosis was determined using a diagnostic interview. The schizotypy group was significantly impaired relative to the nonschizotypy group on neuropsychological test scores spanning domains of attention, verbal memory, and executive functioning. A current DSM-IV diagnosis was made for 71% of the schizotypy group and 43% of the nonschizotypy group. Individuals were classified as having met criteria for schizotaxia if they had a negative symptom impairment and a neuropsychological impairment in two domains. A total of 7 people of 29 met criteria for schizotaxia, 6 of these people were from the schizotypy group. There was statistical evidence that Meehl�s (1962, 1989, 1990b) schizotypy and Tsuang et al.�s (1999b, 2000a, 2000b) schizotaxia are not independent. The proposed precursors for schizophrenia may reflect the same construct, not separate entities. Limitations and implications of these results are considered.

Thesis (Ph. D.)--University of North Carolina at Greensboro, 2007. / Title from PDF t.p. (viewed Feb. 29, 2008). Directed by Thomas R. Kwapil; submitted to the Dept. of Psychology. Includes bibliographical references (p. 79-111).

Thesis (Ph. D.)--Miami University, Dept. of Psychology, 2008. / Title from second page of PDF document. Includes bibliographical references (p.45-55).

Thesis (Ph. D.)--University of North Carolina at Greensboro, 2006. / Title from PDF title page screen. Advisor: Thomas R. Kwapil; submitted to the Dept. of Psychology. Includes bibliographical references (p. 39-55).

Schizotypy as a research framework for schizophrenia emphasizes a link between the symptoms of the disorder and schizotypal traits in the non-clinical population, and argues for a symptom orientated approach to the field. One such symptom area concerns that of unusual experiences, such as hallucinations and delusions that occur in both schizophrenia and in the normal population, but differ in intensity and frequency. Hallucinations and delusions are affected by the environment in which they occur, such as a perceptually ambiguous environment. However, given that both hallucinations and delusions are misinterpretations of the current environment, the content of both could also be influenced by previous experiences, where properties of previous experiences interact with the current environment to produce such experiences. One factor that could influence hallucinations and delusions in this way is time. That is, it could be that those individuals more prone to hallucinations and delusions have stronger temporal links with the properties of previous experiences that facilitate hallucinatory and delusional experiences. The current thesis explores the relationship between the influence of environmental properties on hallucinatory reports and the possibility of differences in timing between individuals scoring high or low in schizotypy through tasks that incorporate temporal elements for optimum performance, such as time based schedules of reinforcement, or measure timing more directly, such as temporal bisection tasks. Findings from the thesis show that high schizotypy scorers make more hallucinatory-like reports than low scorers and that those reports are linked to properties of the environment in which they occur. In addition, there is some evidence that high scorers differ in timing across both schedule and temporal bisection tasks, but only under very specific circumstances.

Title from PDF of title page (University of Missouri--Columbia, viewed on Apr. 12, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. John Kerns. Includes bibliographical references.

Thesis (M.A.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Aug. 28, 2007. Includes bibliographical references (p. 44-60).

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 42-48). Also available via the World Wide Web.

Individuals diagnosed with schizotypal personality disorder (SPD) exhibit patterns of cognitive deficits in (1) attention (Lees-Roitman, Cornblatt, Bergman, Obuchowski, Mitropoulou, Keefe, Silverman, & Siever, 1997), (2) memory (Bergman, Harvey, Lees-Roitman, Mohs, Margerm, Silverman, & Siever, 1998), (3) executive functioning (Cadenhead, Perry, Shafer, & Braff, 1999), and recently (4) neuromotor functioning (Neumann & Walker, 1999), similar to individuals with a diagnosis of schizophrenia. Furthermore, recent research suggests a link between neuromotor and cognitive functioning in schizophrenia spectrum disorders (SSDs) (Neumann & Walker, 2003). The current study is an extension of research on non-drug-induced neuromotor disturbances in individuals with SPD and examines how such disturbances covary with neurocognitive measures. Approximately thirty-three adults (18-65) were rated for SPD symptoms. Motor assessments included a computerized motor task and finger tapping test. Cognitive assessments included measures of attention, verbal and visual memory, and executive functioning. Consistent with previous research, the SPD group displayed significant right hand (left hemisphere) motor disturbances (i.e., increased force and force variability) compared to healthy controls after excluding all cases reporting a history of head injury. In addition, results indicate significant associations between motor, cognitive, and symptom variables. Consistent with previous research, neuromotor functioning and the relationships between motor and cognitive functioning varied as a function of Time of Day (TOD) of testing. Understanding the relationship between neuromotor and neurocognitive functioning may help elucidate the neural systems that contribute the symptoms characteristic of SSDs.