166 Table 1. Group means and standard deviations, as well as betweengroups P values, for sensory thresholds, calibrated temperatures, and reported pain during the acquisition and extinction phases. Group Control High-Pain High-Fear All groups betweengroups P value * Mean SD Mean SD Mean SD Mean SD C° warmth threshold 33.9 0.8 33.7 0.6 33.8 0.6 33.8 0.7 0.46 C° heat pain threshold 43.8 2.4 43.3 2.7 43.3 2.2 43.5 2.4 0.65 C° moderate heat pain 45.8 1.1 47.5 0.9 45.9 1.3 46.4 1.4 < 0.001 C° high heat pain 47.7 0.7 49.1 0.7 47.7 0.9 48.1 1.0 < 0.001 NRS control trials 2.9 1.2 4.7 1.3 2.7 1.1 3.4 1.5 < 0.001 NRS nocebo trials 5.8 1.3 7.9 0.9 6.0 1.1 6.5 1.4 < 0.001 Note: Pain scores are reported on a 0-10 pain Numerical Rating Scale (NRS). Significant differences were found between the High-pain group and the other two groups (P < 0.001), driven by the administration of higher pain levels in this group. Acquisition of nocebo hyperalgesia The mean magnitudes of nocebo responses are presented in Table 2. Figure 4 illustrates differences in pain ratings for the first nocebo and first control extinction trials, across all three groups. High-pain group Nocebo responses in the High-pain group were of almost double the magnitude compared to Control. The analysis revealed a significant interaction between group (High-pain vs. Control) and trial type (nocebo vs. control) (F (1,46) = 4.32, P = 0.04, ηp 2 = 0.09), indicating
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