Chapter 5 – Experimental fear 181 larger nocebo responses, but these responses can also be persistently higher after an initial period of extinction. While these findings linking higher pain levels to larger nocebo responses are in line with research into fear and pain chronification, there are some notable differences. Fear-avoidance models 22,30,54 propose that upon the experience of pain symptoms, patients with painrelated fear engage in a negative feedback loop in which fear-avoidance and reduced physical activity lead to increased disability and psychological strain 54. In our study, participants did not engage in avoidance behaviors, yet our results support a separate pathway to pain chronification, in which fear of high pain may be conditioned in parallel with the nocebo response, thereby significantly strengthening the learning process in nocebo hyperalgesia. In the High-threat group, only startle responses were significantly higher than in the Control group and nocebo magnitudes were not affected by the threat manipulation. Previous research also concluded that experimental threat induction is challenging 22,30. In this study, we informed participants that they may experience sudden, intense pain due to unusual skin sensitivity. Participants were constantly exposed to a mock measurement of this skin test and were reminded to be alert to changes in their sensations. This group generally reported believing the manipulation and being significantly more frightened by it, compared to the Control group that was told that their skin was safe. This may indicate that the threat manipulation did not have a direct effect on participants’ learning, not because of a lack in credibility but perhaps due to the potential negative effects being only anticipated and never actually experienced, unlike in the High-pain group. It is also possible that participants felt relatively safe and anticipated that no harm would be caused (based on their understanding of ethical standards in research). Differences in learned fear responses resulting from experienced versus anticipated threat have been highlighted in the fear literature 55 and
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