Thesis defence : Thomas CHAZELLE

Body representation is the set of cognitive functions that enable the state of the body to be monitored. It is involved in a variety of situations, such as the perception of the body's physical dimensions, action and attitudes to the body. To perform these functions, it relies flexibly on a range of sensorimotor information, as well as on the individual's beliefs, expectations and emotions. Among the sources of information available about the body, social influence can be a factor in the risk, maintenance and severity of body image distortions, particularly in young women. However, while the social influence on the attitudinal aspects of body representation is well established, there is little experimental evidence of such influences on the physical perception of corpulence. The first axis focuses on interpersonal influence by testing the effect of weight labels on judgements of corpulence. Weight labels can be conceived as sources of information about body size. To investigate their informational influence, we varied the reliability of several sources of information to study how they were combined to produce perceptual judgements. Our results indicate that the contributions of memory and vision appear to outweigh those of social influences. A second axis focuses on another type of social influence, media influence. Visual overexposure to certain body types is associated with body dissatisfaction, and could help to explain certain distortions in perceptual body image. In this context, visual adaptation to bodies could explain how prolonged exposure to thin bodies can lead to an overestimation of one's own corpulence. We have carried out several studies to test certain hypotheses of this adaptive theory of body image distortions. These experiments highlight certain limitations of the adaptive theory; in particular, it is uncertain whether adaptation effects can influence the representation that individuals have of their own bodies. In conclusion, our results indicate that the perception of corpulence may be more resistant than expected to social influences.