Body size illusions influence perceived size of objects: a validation of previous research in virtual reality

Abstract

Previous research indicates that the size of the own body affects the judgment of objects’ size, depending on the amount of subjective ownership toward the body (Van der Hoort et al. in PLOS ONE 6(5):e20195, 2011). We are the first to transfer this own-body-size effect into a virtual environment. In a series of three experiments, participants (N = 68) had to embody small, medium, and large avatars and judge the size of objects. Body ownership was manipulated using synchronous and asynchronous touch. We also included a new paradigm with an additional change of perspective to induce stronger ownership (Experiment 2). Additionally, we assessed whether the visibility of the body during the judgment phase influenced the results (Experiment 3). In all three experiments, we found an overestimation in a small and an underestimation in a large body compared to a medium body. However, size estimation did not depend on the degree of ownership despite clear differences in self-reported ownership. Our results show that a virtual reality scenario does not require a visuotactile manipulation of ownership in order to evoke the own-body-size effect. Our validation of the effect in a virtual setting may be helpful for the design of clinical applications.