The experiments presented in this thesis were designed to explore cues to body size judgements previously documented in the existing literature, investigate differences in perception of size (over- and under-estimation) across different groups, and delve into the possibilities of altering the overestimation of size found in sub-clinical populations. The first studies (Chapter 2) aimed to not only reproduce the findings of the effect of hunger on body size preferences previously documented, but also determine whether body size preferences are determined by physiological (hunger) or psychological (time until satiation) cues. Studies in the third chapter aimed to investigate alternative cues, previously not investigated, which influence judgements of the body, i.e. torso length as a predictor of curviness. Chapter 4 involved an investigation into Contraction Bias in relation to the overestimation of body size, and whether this phenomenon is affected by individual variation in observer psychological state and BMI. Following on from this idea, the subsequent study (Chapter 5) investigated the possibility of reducing this overestimation of size in subjects with marked concerns about their bodies (and also reducing factors comorbid with Eating Disorders as secondary effects). These results suggest that more research is needed to investigate psychological and physiological cues behind differences in body size preferences, torso length can be used as a reliable cue to both curviness and body size in the absence of any other cues, overestimation of body size is modulated by observer BMI and psychological state, and that perception training is a possible effective technique for reducing this overestimation. Overall the most important findings in this thesis indicate that treatment for Anorexia Nervosa should take into account the idea that patients’ attitudes to their own body shape, and their self-esteem is reinforced by a perceptual over-estimation of body size, and that strategies should therefore focus not only on the Cognitive component of Body Image Distortion, but also on the Perceptual Component; potentially combining perception training with cognitive therapies.