How Thin Is Too Thin? Evidence from Visual Aftereffects in Body Size Estimation

Exposure to unrealistic body ideals on social media may distort how individuals perceive their own bodies, potentially leading to increased body dissatisfaction. One proposed mechanism for this phenomenon is visual adaptation: prolonged exposure to thin bodies can shift subsequent judgments of body size. This study investigated whether exposure to body images of varying thinness alters body size perception and whether these aftereffects are moderated by individual differences in body image concerns. Thirty-four young women completed a psychophysical task in which they judged whether test bodies were thinner or fatter than themselves, following adaptation to either an extremely thin or a slightly thinner (but closer-to-self) body. Results showed stronger aftereffects following exposure to extreme-thin adaptors, with clear shifts in perceived body size. A significant correlation was found between the average Point of Subjective Equality and body concern, showing that individuals with higher concern estimated their bodies as larger. These findings support the role of visual adaptation in body size perception and suggest that individual differences in body concern influence this process. Opponent coding may underlie this mechanism, as greater aftereffects emerged for more extreme adaptors.