Abstract
Distortions of the experienced size and shape of the body (i.e., the body image) are a conspicuous feature of several serious clinical disorders, including anorexia nervosa and body dysmorphic disorder. A large literature has used body size estimation methods to compare body image in patients and healthy controls. A general finding, supported by several previous meta-analyses, is that patients with eating disorders overestimate body width relative to controls. Here, I investigated performance on these tasks in healthy adults, focusing on the control groups from studies investigating patients and on studies of non-clinical samples. A total of 632 studies were identified using body-size estimation methods. From these, non-clinical adult samples were selected, excluding samples designated as having any clinical disorder, such as an eating disorder, obesity, or schizophrenia. Overestimation of body width was calculated for two types of tasks: depictive tasks in which the participant compares their body to a visual image of a body (e.g., the distorted picture or video distortion tasks), and metric tasks in which the participant compares the perceived size of part of their body to a metric standard (e.g., the moving caliper and image marking tasks). In both cases, I focused on judgments in the frontal body plane. For each task, random-effects meta-analysis was used to estimate the mean percentage overestimation of body width and its 95% confidence interval. Despite considerable between-study variability, depictive tasks showed no evidence for systematic deviation from veridical judgments (see Supplemental Figure). In contrast, metric methods showed systematic overestimation of body width, ranging from 10-20% across tasks. Importantly, judgments of non-body objects showed no such distortions, indicating that the overestimations of body width are not an artefact of task demands. These results show that distortions in body image are not exclusive to disease, but are a normal part of healthy cognition.
Meeting abstract presented at VSS 2018