Body image; representation and constraints on measurement in real and virtual worlds

Body image is a multidimensional construct that embraces a person’s conscious perception of their physical self, including the thoughts and feelings that result from that perception. Disturbed body image can lead to dramatic attempts by the individual to alter their appearance, for example through self-starvation in eating disorders such as anorexia nervosa. Body image comprises two independent modalities: i) a perceptual component that has to do with the accuracy with which a person can judge the dimensions of their own physical appearance, and ii) an attitudinal component which captures the feelings that a person has about their body size and shape. This thesis explores perceptual body image, with a focus on body size estimation, in samples of non-eating disordered women from three points of view. Firstly, individuals who have eating disorders are known to experience a diverse range of disturbances in body representation. In study one, we sought to investigate how attitudinal and perceptual body image may normally be expected to interact with motoric representations in the body scheme. To this end we tested a moderated mediation model which showed that perceptual body image only mediated performance on an egocentric motor imagery task in women with raised body image concerns and low self-esteem. We concluded that the affective salience of a distorted body representation mediates the degree to which it is incorporated into the current body state. Secondly, in studies 2-4 we used a modified version of the Bubbles masking technique, in combination with eye movement recording, to discover the visual cues that women use to make perceptual body image judgements. We found that although observers fixate centrally on the torso when making body size judgements, nevertheless they direct their visual attention to the edges of the torso, to gauge width as an index of body size. Based on this dissociation, we conclude that central fixations are simply the most efficient way of positioning the eye to make size judgements. Next, in studies 5 and 6, we investigated the feasibility of body size estimation using 3D stimuli in immersive virtual reality (VR). In a sequence of experiments, we show: i) how a bespoke avatar can be created from 2D photographs; and validated ii) that participants can identify the presence of their own avatar amongst others, despite anonymization by facial masking; iii) that participants are more accurate at estimating their body size with a bespoke avatar than a standard 3D model in VR. Lastly, in study 7 we replicated and extended an existing body image intervention, known to work in 2D on a flat panel monitor screen, by testing it in VR. We successfully raised individuals’ perceptual boundary for thin versus fat body sizes. This perceptual retraining led to reductions in psychological concerns about body shape, weight and eating; effects that persisted for up to two weeks post-training, some of which were more potent in VR than 2D