Chapter 4 – Experimental learning 119 indicating higher trait anxiety. Cronbach’s alpha was 0.83 in this study. The Pain Catastrophizing Scale (PCS) 29 was used to assess catastrophizing thoughts related to pain, with scores ranging from 0 to 52, where higher scores indicate more frequent catastrophizing thoughts. Cronbach’s alpha was 0.87 in this study. The revised Life Orientation Test (LOT-R) 30 was used to measure dispositional optimism versus pessimism. Scores on this questionnaire range from 0 to 24, with higher scores indicating higher optimism. Cronbach’s alpha was 0.69 in this study. Participants were also asked to rate their tiredness on a 0-10 NRS scale from “not at all” to “very much”. Moreover, a screening questionnaire containing demographic and health questions was used to screen participants for inclusion in the study. At the end of the experiment, participants completed an exit questionnaire containing manipulation check questions assessing pain expectations (rated on the pain NRS), how much they trusted the experimenters, and how honest they thought the experimenters were (rated on a 0-10 NRS from “not at all” to “very much”). The exit questionnaire also assessed whether participants believed the cover story or were aware of the real purpose of the experiment (i.e., the manipulation of expectations or use of conditioning). All questionnaires, as well as a debriefing from, were displayed on a tablet via web-based survey software (Qualtrics, Provo, Utah, USA). Experimental Procedure On the day of the appointment, participants were first provided with information about the experiment and were asked to provide written informed-consent. Then, participants completed the screening and the psychological questionnaires. Following this, they read the information sheet about the (sham) pain enhancing effects of the TENS device. Warmth and pain threshold levels were then tested and individual pain
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