Chapter 5 – Experimental fear 151 Materials and Methods Design This study utilized a randomized, mixed (between-within-subjects), three-group design (Figure 1). A randomization list was created by an independent researcher to reduce any risk of bias. All participants underwent nocebo acquisition and extinction procedures by use of classical conditioning and negative verbal suggestions. In the acquisition phase, the Control group and High-threat group were conditioned with moderate pain intensity stimuli during nocebo trials, while the High-pain group was conditioned with high pain intensity stimuli during nocebo trials, with the aim to additionally induce and examine increased painrelated fear in this group. The High-threat group received a threat manipulation, with the aim to additionally induce and examine increased pain-related fear in this group. Participants The required sample size for the primary analysis was calculated based on our previous nocebo study 5 comparing the magnitude of nocebo responses between three groups that received different conditioning manipulations. The analysis was conducted in G*power 3.1 26 for a mixed model ANOVA. The effect size was f = 0.26, alpha error probability was set at α = 0.05, and desired power was set at 0.95. The sample size indicated was 21 participants per group. Given that previous studies that included fear manipulations with similar study designs included samples of 20 to 25 participants 22 and due to the novel manipulations used in this study we aimed to include 24 participants per group. This sample size is similar to previous studies examining between-groups differences using conditioning manipulations 25,27.
RkJQdWJsaXNoZXIy MTk4NDMw