The Role of Learning in Nocebo Hyperalgesia

Main planned analyses: Primary Outcome; Comparing the effectivity of conditioning with PRF, conditioning with CRF, and sham conditioning, in inducing nocebo effects on pain: The magnitude of the induced nocebo effect during the first evocation phase (dependent variable), will be compared between induction groups (independent variable). The pain ratings for the first control trial will be measured against the pain ratings for the first reinforced trial, yielding the magnitude of the nocebo effect. A 3x2 mixed model Analysis of Variance (ANOVA) will be used, treating group as the between-subjects factor with three levels (PRF, CRF, sham) and magnitude of the nocebo effect on pain as a within-subjects measure with two levels (first control and first reinforced trial). Planned contrasts will be conducted. Secondary Outcome; Comparing the effectivity of counterconditioning and extinction in attenuating nocebo effects on pain: The nocebo effect still present in the second evocation phase (dependent variable) will be compared between attenuation groups (independent variable). This effect will be measured as the change in pain ratings reported in the first reinforced trial of the first evocation phase (after induction) and pain ratings reported in the first reinforced trial of the second evocation phase (after attenuation). This effect will be further analysed by measuring any change in pain reports for the control trials (second dependent variable) in the same way. The effect of induction group will also be further explored. A 2x2 mixed model ANOVA will be conducted, with attenuation group as the between-subjects factor (counterconditioning and extinction) and the degree to which the nocebo effect has been attenuated as the within-subjects measure with two levels (first and second evocation phase for the first reinforced trials). Further secondary analyses will be conducted.