Chapter 5 – Experimental fear 159 attached to the hand and arm and a short mock calibration took place. Participants were asked to wear earphones and were exposed to 5 startle probes in order to achieve startle probe habituation. Then, participants underwent the nocebo acquisition and extinction procedure. After the end of the experiment participants were asked to answer the exit questions and complete the psychological questionnaires. Then, participants were debriefed and reimbursed. Reimbursement by cash or study credits was, by chance, equally distributed over groups. Response Definition and Statistical Analyses Behavioral data were analyzed by use of SPSS 23.0 (IBM Corp., Armonk, NY, USA). For all analyses, the threshold for significance was set at P < 0.05, and where multiple comparisons were performed a Bonferroni correction was used. Partial eta-squared (ηp 2) was computed as an effect size measure, with ηp 2 of 0.01 considered small, 0.06 considered medium, and 0.14 considered a large effect size 38,39. To conduct mixed model analysis of variance (ANOVA), assumptions of normality, and homogeneity of the variances were checked. The assumption of independence was achieved by randomization of participants into groups. For mediation analyses, non-parametric and bias-corrected bootstrapping was used 40. The independent errors assumption was checked with the Durbin-Watson statistic and multicollinearity was tested through variance inflation factor (VIF). Pain outcome measures Mean pain scores were calculated per trial type for each participant and nocebo magnitudes were measured within-subjects. The magnitude of
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