| Summary: | <p>Pain is a multi-faceted psychological concept, having sensory, affective, motivational, and cognitive aspects. It is an interoceptive signal, one that alerts the person of actual or potential tissue damage that needs to be eliminated. Expectation is one of the cognitive modulators of pain perception, resulting in well-established phenomena such as placebo effects, where the expectation of pain relief attenuates the perception of pain intensity. Atypical sensory sensitivity is one of the diagnostic criteria in autism, a highly heterogeneous neurodevelopmental condition. Studies on pain perception in autism have repeatedly found mixed results, and studies investigating the cognitive modulation of pain in autism are limited. Furthermore, few take into account individual differences within the autism spectrum. This thesis seeks to fill these gaps in research on cognitive modulation of pain, in particular, modulation of pain by expectation, in autism, while taking individual differences in autistic and non-autistic (particularly alexithymic) traits into account.</p>
<p>Chapter 1 provides a general overview of pain, and autism. Theoretical frameworks applied in the empirical chapters, such as cognitive accounts of pain perception, the Bayesian account of autism, and the alexithymia hypothesis, are outlined and reviewed.</p>
<p>Chapter 2 compares sub-clinical levels of mental health symptoms in the general population and a typical psychology study participant pool. This chapter aimed to assess the prevalence of common mental health traits in psychology volunteers compared to the general population, and whether these symptoms, even at sub-clinical level, could affect standard cognitive tasks. Results showed that there are sub-groups within our psychology volunteers, who all showed elevated levels of mental health symptoms compared to the general population. There were also significant differences in cognitive task performance between these sub-groups.</p>
<p>Chapters 3 and 4 investigate the effect of expectation on pain perception, where expectations are presented in the form of a cue and are of fixed values. In Chapter 3, a placebo hypoalgesia paradigm is employed to assess whether the magnitude of the placebo effect (i.e., how much expectation is incorporated into perception) is modulated by either autistic or alexithymic traits. Results showed it is alexithymic traits, not autistic traits, that predict the magnitude of the initial placebo effect. In Chapter 4, the effect of prediction error size and valence on pain perception is investigated using a novel prediction error size paradigm. Results showed that, in line with the previous study, the magnitude and the valence of prediction error impacted pain perception. Autism modulated this effect, while alexithymia modulated how this effect changed over the course of the task.</p>
<p>Chapter 5 investigates the effect of expectation on sensory perception using probabilistic cues. Two experiments, one using pain stimuli and another using visual stimuli, are conducted to assess whether the effect of autism or alexithymia on cue integration, if any, is limited to the interoceptive domain, or can also be observed in the exteroceptive domain. Results showed no effects of autism or alexithymia, though the matter remains unclear due to an observed ceiling effect.</p>
<p>Chapter 6 discusses the findings of this thesis in a wider context, and its implications in the field of pain, autism, and alexithymia research.</p>
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