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  • One hundred and six volunteers were recruited through local advertisements and circular emails. Participants were screened for clinical exclusion criteria and provided demographic and psychometric personality information. Clinical exclusion criteria were (1) any current psychiatric diagnosis (using the German version of the Mini-International Neuropsychiatric Interview [28]), (2) history of neurological complications, (3) history of psychosis or ADHD in first-degree relatives, (4) any current physical condition, (5) any current consumption of over-the-counter medication, prescription medication (except for contraceptives) or psychotropic drugs, (6) colour vision deficiency. In addition, subjects whose first language was not German were excluded. All subjects completed the study and met the criteria. The study was approved by the ethics committee of the Faculty of Medicine of the University of Munich (Ethikkommission der Medizinischen Fakultät der LMU). Subjects provided written informed consent and were reimbursed for their participation. Demographic data were collected using a questionnaire asking among other for age, gender, and years of education. Schizotypy was assessed using the German version of the schizotypal personality questionnaire (SPQ) [12], [29]. The SPQ is a self-report scale based on DSM-III-R criteria for SPD [30]. It contains 74 items with a two-point response format (yes/no) yielding subscales for the nine different DSM-III-R schizotypal traits: Ideas of Reference (IR, 9 items), Social Anxiety (SA, 8 items), Magical Thinking (MT, 7 items), Unusual Perceptual Experiences (UPE, 9 items), Eccentric Behaviour (EB, 7 items), No Close Friends (NCF, 9 items), Odd Speech (OS, 9 items), Constricted Affect (CA, 8 items) and suspiciousness (S, 8 items). Thereby, IR, MT, UPE and S refer to positive schizotypy whereas SA, NCF and CA refer to negative schizotypy. Finally, disorganization is defined by the SPQ subscales EB and OS. The SPQ questionnaire has high internal reliability (.91), test-retest reliability (.82) and validity [12]. In the present sample the SPQ had high internal reliability (.91). The items were coded as 1 for “yes” and 0 for “no”. For the total SPQ mean score, the mean value across all 74 items was calculated; for the 9 subscales the mean score was calculated across the corresponding items. Neuroticism (N) was assessed using the German version of the NEO-FFI [31], consisting of 12 items. The items use a five-point Likert-type response format (“strongly disagree” = 0; “strongly agree” = 4). In the current sample the N subscale had high internal reliability (.82). Verbal IQ was estimated using the MWT-B [32]. In this test subjects are required to identify a real word among four non-words in each row. A correct answer was coded as 1, an incorrect answer as 0. A maximal score of 37 could be obtained. The stimuli consisted of the German words “ROT” (red), “GRÜN” (green) or “BLAU” (blue) shown in either red, green or blue ink, on a notebook computer (Dell Latitude, D430) with a 12.1-inch screen. Trials were considered either congruent or incongruent depending on whether word and ink colour were the same (e.g., the word “ROT” in red ink) or not (e.g., the word “ROT” in green ink). Subjects were instructed to name the ink colour as fast and accurately as possible by pressing the arrow keys “left”, “down”, “right” with their right ring finger, middle finger, and index finger, respectively. In the beginning of every trial there was a fixation cross (approximately 0.6° of visual angle; distance to screen approx. 57 cm) presented in the centre of the screen for 1 sec followed by the colour word (vertical size approx. 0.8°, horizontal size approx. 3.0° of visual angle) that stayed on the screen for a maximum of 2 sec or until the subject pressed a button. After a pause of .5 sec, a new trial began. There were two blocks of 99 trials each with a short break between blocks. In total, there were 138 congruent trials (69.7%) and 60 incongruent trials (30.3%). In the beginning of each block 6 congruent trials were presented in succession to increase the interference effect (see Kerns et al. [6]). These 12 trials across both blocks were excluded from further analysis. All other trials were presented in a randomized order. The experiment took about 12 minutes. Statistical analysis was carried out using the Statistical Package for the Social Sciences, Release 17.0 (SPSS Inc., Chicago, IL). For the initial analysis of post-conflict adjustment the significance level was set at p<.05 and p-values between .05 and .1 were considered trends. For the subsequent correlation analyses of the SPQ scale and subscales the significance level was set at 0.005 to account for multiple comparisons using the Bonferroni correction; p-values between .005 and .01 were considered trends. Following Kerns et al. [6], only trials that did not represent either an ink colour or word repetition were used. This procedure controls for partial priming effects between subsequent trials, which may be related to repetition of word or colour information between trials [33]. Additionally, error and post-error trials were excluded to account for effects of post-error slowing (on average 7 trials were excluded per subject). Trials were categorized according to congruency and incongruency in the current and in the previous trial. Consequently, there were two factors yielding trials from four categories: congruent trials preceded by congruent trials (cC), congruent trials preceded by incongruent trials (iC), incongruent trials preceded by congruent trials (cI) and incongruent trials preceded by incongruent trials (iI). Reaction time (RT) data were analyzed by repeated measures analysis of variance (ANOVA) with the factors “congruency of present trial” and “congruency of previous trial”. On the basis of significant interactions, post-hoc t-tests using Bonferroni-correction were calculated. The basic Stroop effect was calculated with the following formula: RT (incongruent current trials)−RT (congruent current trial). Post-conflict trial-to-trial adjustment was calculated identical to Kerns et al. [3]: [RT(iC)−RT(cC)]+[RT(cI)−RT(iI)], i.e. the higher this adjustment score, the more the participants improved their performance in the post-conflict trial. Pearson correlations were carried out to assess associations between post-conflict adjustment and schizotypy and between schizotypy and N. Additionally, in order to control for possible effects of age, sex, years of education, verbal IQ, and N partial correlations were carried out. Thereafter, a linear regression model was calculated to predict post-conflict adjustment from the 9 SPQ subscales. The subscales were introduced as predictors in one block using the stepwise method (probability for entry set at .05) in order to identify the strongest predictors of post-conflict adjustment. In a further regression analysis, we investigated the impact of N on the relationship between SPQ subscales and post-conflict adjustment. We first introduced Neuroticism as covariate in the regression model. In a second step we introduced the subscales using the stepwise method (entry probability set at .05). SPQ mean score was positively skewed (skewness = 1.63). A square root transformation normalized the skew (0.31). Using square root transformed scores instead of untransformed variables did not change the pattern of significant findings with regards to post-conflict adjustment. For that reason, and to make the correlation results more compatible with the descriptive data, untransformed variables were used in all analyses presented here.
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