Chapter 4 – Experimental learning 141 information provided to participants in the partial reinforcement group and the formation of mixed expectations regarding the activation of the nocebo treatment. The partial reinforcement-counterconditioning group was exposed to a wider range of negative and positive suggestions and associations. It is possible that during the final evocation the negative treatment associations were retained over the positive ones. A resistance to the attenuation with counterconditioning may thus be in line with previous literature about this type of negativity bias 44. This effect may be of important clinical relevance, as it could shed light on the etiology of pain chronification following exposure to inconsistent, mixed information and experiences. In turn, however, this means that the potency of counterconditioning following ambiguous and variable learning remains uncertain. Gaining a better understanding of the learning mechanisms underlying the process of re-writing negative associations can create great future value for counterconditioning. One limitation of this study, as mentioned earlier, was the discrepancy in the length of induction and attenuation, which may explain why nocebo responses were not resistant to extinction. Colagiuri and colleagues 15 only applied extinction, allowed the paradigm to comprise an equal number of induction and attenuation trials. In the current study, due to our aim of comparing counterconditioning and extinction, a longer evocation phase was preferred before the start of attenuation. Participants were thus exposed to longer extinction, as compared to induction. Nevertheless, in clinical contexts and chronic pain, unequal lengths of exposure to suggestions, learning, and extinction may also exist. Future research should address the role that the time-course of induction and attenuation may play. Another limitation of this study and a common obstacle in nocebo studies, was related to the nocebo suggestions. In this novel counterconditioning approach, the suggestions had to indicate that the same treatment could increase but also decrease pain sensitivity. The suggestion that pain would be decreased by the same device that previously increased pain sensitivity
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