The University of ManchesterCandidate: Ann Patricia WatkinsonA thesis submitted to the University of Manchester for the degree of Master of Philosophy in the Faculty of Medical and Human Sciences in October 2013Thesis title: Pain Ratings Reflect Cognitive Context: A Range Frequency Model of Relative Pain JudgementsThis thesis presents an investigation into context-dependent evaluation of pain intensity. A literature review set out to explore different approaches to pain evaluation. It particularly looked for evidence of assumptions of absolute pain judgement (made in isolation about a current painful event) and also evidence of relative pain judgement, dependent upon circumstances or context. The review of approaches to relative pain evaluation was restricted to literature describing cognitive and emotional factors contributing to pain ratings and did not include any investigation of the sensory, physiological, neurological or genetic aspects of pain. The review identified that although some research and clinical practice has implicitly assumed pain judgements to be absolute and made in isolation, other research has investigated relative pain judgements which can vary depending on the context in which pain is experienced. Many researchers have suggested that pain evaluation involves cognitive and emotional as well as sensory and physiological factors. However, few have proposed a cognitive explanation for relative pain judgements, and there has been no quantitative model established to describe the cognitive mechanism underlying such judgements. Developments in general understanding of relative psychophysical and socioemotional judgements were explored, and Range Frequency Theory was identified as a potential quantitative model of the cognitive mechanisms underlying context-dependent pain evaluation. This was explored in two empirical studies presented in this thesis as a published article. The two studies used pressure pain stimulation to test the two principles of Range Frequency Theory against competing potential models of relative judgement. Study 1 tested the rank (or frequency) principle of Range Frequency Theory, and illustrated that the same objective painful stimulus was rated as more intense, the higher it ranked in the context of other painful stimuli. Study 2 tested the range principle of Range Frequency Theory, and illustrated that pain ratings were higher when most stimuli were relatively intense, despite the average of all stimuli in the context remaining constant. Together, these studies provided empirical evidence that pain judgements are made relative to other pain experienced, and that Range Frequency Theory provides a good model of the cognitive processes underlying such judgements. These results complement the existing body of research into context-dependent pain evaluation and suggestions are made for further research to better understand the interaction of these complementary approaches.