Underestimation of human hand density

Abstract

Our body is a 3D object, with physical properties such as volume, weight and density. Our brain has to represent these physical properties in the perception of one's own body and body parts. It has been shown that we have a distorted representation of hand size and hand weight. In this study, we investigated the perception of hand volume without experimental alterations. We found that people overestimate the volume of their hand on average by 24%, relative to its actual volume, and we replicated the hand weight underestimation by 25% relative to its actual weight. With a precise estimation of perceived hand volume and hand weight, we calculated perceived hand density. The mean perceived hand density was .75 g/cc, comparable to foam beads, an underestimation of 31% of actual hand density. Our findings suggest that the brain maintains a stable representation of hand density at a low level, with perceived hand weight and volume adjusting accordingly, rather than being estimated independently. Our results add to a body of evidence showing that the representation of our body parts is inherently distorted. This study contributes to the understanding of how volume, weight and density are estimated in the perception of body parts, and the relationship between the representations of physical bodily properties.