154 administered during nocebo trials, to condition participants to expect increased pain as a result of the inert nocebo (i.e., sham electrical stimulation). Administered pain stimuli during nocebo acquisition and extinction During the acquisition phase (described in detail directly below), 12 nocebo and 12 control stimuli were administered in pseudorandom order, so that no more than three trials of the same type were administered in a row. During the extinction phase (also described below), 12 nocebo and 12 control stimuli were administered in pseudorandom order. To reduce habituation or sensitization to heatpain, the thermode was moved twice to a more proximal site on the same arm (at one third and two thirds of the paradigm). Nocebo manipulation A commercial Transcutaneous Electrical Nerve Stimulation (TENS) device (Beurer EM 80) was used to deliver (sham) electrical stimuli, which served as the nocebo manipulation in the nocebo acquisition and extinction procedure, as it represented an inert treatment that was not actually activated in the main experiment. A sham TENS ‘treatment’ was used to condition nocebo hyperalgesia that may be more ecologically valid, in that negative pain expectations are induced about the effects of a (sham) treatment stimulus. Negative verbal suggestions were used to create expectations regarding the pain-enhancing effects of administering electrical stimuli in combination with thermal pain. Two electrodes (Medi-Trace 200 EKG, 35mm) were placed in a diagonal line on the base of the thumb and the inner elbow. Prior to the start of the acquisition phase, participants underwent a short mock calibration
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