Being Barbie: The Size of One’s Own Body Determines the Perceived Size of the World

TLDR

The sense of one's body may influence visual perception of size and distance, a hypothesis supported by theorists but lacking experimental evidence, whereas textbooks attribute perception to multiple visual cues. The study uses full‑body ownership illusory bodies of different sizes to test whether perceived body size directly affects object size and distance perception. Ten experiments measured the effects using verbal, questionnaire, manual, walking, and physiological metrics. Participants who owned a tiny body perceived objects as larger and farther, while those who owned a large body perceived them as smaller and nearer, and the effect was stronger with ownership, indicating a causal link between body size representations and external space perception.

Abstract

A classical question in philosophy and psychology is if the sense of one's body influences how one visually perceives the world. Several theoreticians have suggested that our own body serves as a fundamental reference in visual perception of sizes and distances, although compelling experimental evidence for this hypothesis is lacking. In contrast, modern textbooks typically explain the perception of object size and distance by the combination of information from different visual cues. Here, we describe full body illusions in which subjects experience the ownership of a doll's body (80 cm or 30 cm) and a giant's body (400 cm) and use these as tools to demonstrate that the size of one's sensed own body directly influences the perception of object size and distance. These effects were quantified in ten separate experiments with complementary verbal, questionnaire, manual, walking, and physiological measures. When participants experienced the tiny body as their own, they perceived objects to be larger and farther away, and when they experienced the large-body illusion, they perceived objects to be smaller and nearer. Importantly, despite identical retinal input, this “body size effect” was greater when the participants experienced a sense of ownership of the artificial bodies compared to a control condition in which ownership was disrupted. These findings are fundamentally important as they suggest a causal relationship between the representations of body space and external space. Thus, our own body size affects how we perceive the world.