The DSM-IV: APA, diagnosiss schizophrenia based on reoccurring symptoms, including hallucinations delusions, disorganised speech, disorganised or catatonic behaviour and negative. One reason for cognitive impairments observed in schizophrenia is the processing of context. Cohen (1999) states ‘context processing’ is used in general to mean the functioning of mental effort or cognitive control. It is referred to actively holding information to be used to mediate task appropriate behaviour. Buchanan et al (1994) states negative symptoms of schizophrenia are connected with deficits involving executive functioning memory. Further evidence from Dibben, et al (2009) explains executive dysfunction shows difficulty in maintaining contextual information, therefore may be an endophenotype of the schizophrenia spectrum of disorders.
Research has found there are certain negative schizotypy traits, associated with schizophrenia. Lenzenweger (2010) defines schizoptypy as an underlying personality construct rather than a set of explicit behaviours, which may indicate a concealed risk of future schizophrenia. Schizotypy traits which parallel symptoms of schizophrenia vary from low to pathological, suggesting schizophrenia as a spectrum disorder. ‘Schizotypal Personality Disorder’ (SPD) presents as similar symptoms to schizophrenia but are explained as a border line state in DSM-III (APA, 1980) SPD not severe enough to meet the criteria to be diagnosed as schizophrenic. Therefore signifying schizophrenia corresponds to the severe end of the spectrum. Additional support from O’Flynn et al (2007) shows individuals with high schizotypy scores are cognitively linked to schizophrenia as part of a schizophrenia spectrum. Furthermore Diforio (2000) found SPD patients exhibit cognitive impairment in numerous areas, such as executive functioning, dual task information processing and working memory. These are similar to those seen in schizophrenia, although less severe. Studies by Barch (2004) also found individuals expressing schizotypal characteristics express deficits in attention and working memory. Studying individuals with schizotypy traits or SPD can help towards understanding systems and psychological processes contributing to schizophrenia, without confounding factors such as medication effects intervening, which is problematic when researching schizophrenia.
The O-LIFE was developed to focus on traits rather than symptoms. It measures four sub-scales associated with schizotypal traits, all have been recognized to have high internal consistency. These are ‘unusual experiences = 0.89’, ‘cognitive disorganisation = 0.87’, ‘introvertive anhedonia = 0.82’ and ‘impulse nonconformity = 0.77’. (Mason et al 1995) Evidence from Burch et al (1998) found O-LIFE’s test-retest reliability to be very high. However this investigation just measures introvertive anhedonia commonly referred to as a negative schizotypy trait.
Meehl (1962) states Anhedonia is the reduced ability to experience social and physical sources of pleasure, as well as avoidance of intimacy, it is an important characteristic of negative symptoms describing it as “one of the most consistent and dramatic behavioural signs of the disease”. Additionally high social anhedonia as suggested by Blanchard et al (2000) may indicate schizotypy, relating it to a taxon amongst an undergraduate population. A study by Kwapil (1998) suggests higher scores of social anhedonia have been correlated to a greater probability of being diagnosed with future schizophrenia.
This investigates uses the O-LIFE questionnaire to measure scores on the introvertive anhedonia subscale and to observe if higher scorers have difficulty with contextual processing. Haddon et al (2011) claim biconditional discrimination in the form of a contextual processing task may be used to measure the way in which task-setting cues control performance. Participants are required to learn relationships by trial-and-error between random pairs of stimuli and feedback responses. Cohen & Servan-Schreiber (1992) propose task-setting cues are essential in resolving conflict which opposing stimulus-response pathways create. A study by Mason et al (1995) examined performance of participants with high and low schizotypy scores, using biconditional discrimination and a control discrimination which did not use task-setting cues. Findings showed those who scored highly on the introvertive anhedonia subscale performed weakly on the biconditional. Therefore Liddle (1987) suggests deficits in biconditional discrimination are directly related to the introvertive anhedonia schizotypy subscale. Furthermore Burch et al (1998) states high schizotypy scores are related to impairments on cognitive tasks, similar to those with schizophrenia.
Looking at previous research this investigation aims to replicate (using a related discrimination procedure) and generalise findings of Haddon et al (2011), also to contribute to developing projects on schizotypy which looks to understand effects of core cognitive deficits on severe mental illness. The investigation hypothesises the high schizotypy group will find completion of biconditional discrimination more difficult than lower groups.
An experimental design was used in this study. The independent variables were the schizotypy groups 1, 2, 3 and 4. The dependent variable was the biconditional discrimination score.
92 undergraduates (75 females and 17 males) participated in return for course credit and were undiagnosed as schizophrenic or taking psychotropic medication.
Materials included the O-life (The Oxford and Liverpool Inventory of Feelings and Experiences) questionnaire and a contextual processing task. (O-LIFE; Mason 1995) This was chosen as it is a reliable and valid measure that was specifically designed for use with sub-clinical populations.
A desktop computer running windows and visual basic was used for displaying the stimuli and recording the participant’s responses. The contextual processing task programme was designed specifically for the investigation.
Participants were tested individually in a quiet environment. The 160-item O-LIFE questionnaire used for measuring schizotypal characteristics within the normal population was shown on a projector screen and participants had to circle yes or no to the corresponding question on an answer sheet. Participants were allocated to schizotypy groups of 20 based on their introvertive anhedonia score relative to the distribution of this trait in participants of similar age and gender. They carried out a contextual processes task which tested biconditional discrimination.
Participants assumed the role of a stockbroker and advised clients on stock profitability. In total of 80 training trials presented the participant with pairs of hypothetical stocks including chemicals and paper or metal and wood. Participants then discriminated on a 9 point scale which pairs of stocks would result in profit (positive outcome) and which would result in losses (negative outcome). Participants were instructed to provide a confidence rating of 1 if certain there would be a loss a rating of 5 if uncertain and a rating of 9 if certain of a profit, feedback was provided on the outcome. All four types of trial (AX, BX, AY, BY) (see fig 2) were presented randomly once within each cycle, 20 trials of each compound in total.
Fig 2 – Table of contingences.
Completing the task involves attending to both cues consecutively to predict important events. When processing one cue (X) participants have to consider the context in which it is displayed (A or B).
As there were multiple levels of the independent variable a one way between ANOVA was used to test for a difference. This analysis decreases chance of a type 1 error. The dependent variable biconditional discrimination was measured by taking the average difference between profit (AX & BY) and loss (AY & BX) trials in the final 40 trials of learning. Analysis was carried out this way because as Haddon et al (2011) show the effects between the groups emerge as learning progresses. A single score ranging from -8 and +8 was therefore produced reflecting each participant’s contextual learning ability. The higher the participants score the more context learning ability they have. As ANOVA only states whether there is an overall significant effect Bonferroni post hoc tests were carried out to find which means were significantly different from each other.
Levenes test of homogeneity of variance is used to report whether variance is significantly different between groups. We cannot use the ANOVA model if there is a significant difference, although for this study Levenes test of homogeneity of variance was non-significant, (p>0.05) therefore ANOVA data can be interpreted.
One way between ANOVA shows an overall significant difference between introvertive anhedonia score and contextual processing. (F (3, 88) = 6.019, p<0.001)
Pairwise comparisons using post hoc test bonferroni showed scores for group 1 were significantly higher than those in group 4 (p<0.001) and group 3 (p<0.05). However there was no significant difference between the scores of group 1 and group 2 (p>0.05). As figure 1 shows a linear association was found. (See figure 1).
Figure 1. Mean discrimination score by group (s.e shown as error bars)
The aim of this investigation was to further examine and replicate the findings of Haddon (2011). Findings have provided evidence consistent with this aim and hypothesis that high schizotypy groups have difficulty completing biconditional discrimination compared to lower groups. Specifically participants with higher introvertive anhedonia scores (group 4) displayed more impaired biconditional performance compared with those with low scores (group 1).
The connection found between high Introvertive Anhedonia scores and impaired biconditional performance is consistent with Liddle’s (1987) research linking cognitive dysfunction to negative symptoms of schizophrenia and schizotypy characteristics. However it is essential to note anhedonia is not an exclusive feature of schizophrenia, having also been found in bipolar disorder.
These results not only give further support to Haddon et al’s (2011) findings but also maintains the theory from Cohen and Servan-Schreiber (1992) that high schizotypy individuals, should be impaired on biconditional discrimination tasks since contextual information is essential for resolving conflict between opposing stimulus-response.
Futhermore the statistical test ANOVA only shows there is a difference between group’s scores, not stating exact cause and effect. Variation within groups could be due to individual differences or other factors that were not controlled (tiredness or mood) could affect concentration. Participants could have found the task uninteresting therefore not engaging fully; also participant’s different approaches to answering biconditional discrimination task can have an impact upon results.
The O-LIFE questionnaire has good test-retest reliability and is useful in studying a nonclinical population. Although O-LIFE is not a diagnostic test for risk of mental illness, testing only personality traits. However there are limitations in the investigation, the sample had a clear gender bias with a larger female to male ratio. Another drawback being a young age bias as it used undergraduate students, although sampling from younger age groups produces groups with comparable distributions of introvertive anhedonia scores.
Further research is needed to determine the significance of these results and their implications for the relationship between negative schizotypy traits and context processing. Researchers looking for objective indicators for causes of decline into schizophrenia could use further research using these results.
Additionally larger understanding of negative symptoms could motivate research into producing therapies effective for negative symptoms.
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