118 pseudorandomized to achieve an approximately even distribution throughout the induction phase). The continuous reinforcement groups received high pain stimuli in 100% of nocebo trials. The control group received sham conditioning, where TENS activation was not consistently paired to the intensity of pain stimuli but rather, this group received high pain in 50% of nocebo trials and in 50% of control trials. In the first evocation phase, all pain stimuli were applied at moderate intensity, preceded by the nocebo and control cues, to evoke conditioned responses. Increased pain reports for the first nocebo trial as compared to the first control trial in this phase indicated nocebo hyperalgesia. During attenuation, the counterconditioning groups received surreptitiously decreased pain stimulations during TENS activation, while TENS deactivation was still paired to moderate pain inductions. During extinction, participants continued being exposed to pain stimuli at only moderate intensity preceded by the nocebo and control cues. During the second evocation phase, all pain stimuli were applied at moderate intensity, preceded by the nocebo and control visual cues, to test whether nocebo responses were diminished after attenuation. Questionnaires Four questionnaires were used to measure baseline differences in psychological characteristics. Total scores were used for all questionnaires. A short State Anxiety version of the State-Trait Anxiety Inventory, (STAI-S) 27,28 was used once before the start (STAI state pre) and once after the end of the experiment (STAI state post). Scores on this questionnaire range from 20 to 80, with higher scores indicating higher state anxiety. Cronbach’s alpha in this study were 0.77 (pre) and 0.74 (post). The State-Trait Anxiety Inventory, Trait version (STAI-T) 27 was also used, with scores also ranging from 20 to 80 and higher scores
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