Self awareness and the body image

What mental representations give us the sense of our body as a unique object in the world? We investigated this issue in the context of the rubber hand illusion (RHI), an illusion of body image in which a prosthetic hand brushed synchronously, but not asynchronously, with one’s own hand is perceived as actually being one’s hand. We conducted a large-scale study of the RHI, and used psychometric analysis to reveal the structure of the subjective experience of embodiment [Longo et al. (2008). What is embodiment? A psychometric approach. Cognition,107, 978-998]. Here, we use this dataset to investigate the relation between incorporation of a rubber hand into the body image and the perceived similarity between the participant’s hand and the rubber hand. Objective similarity (as measured by skin luminance, hand shape, and third-person similarity ratings) did not appear to influence participants’ experience of the RHI. Conversely, incorporation of the rubber hand into the body image did affect the similarity that participants perceived between their own hand and the rubber hand. Participants who had experienced the RHI perceived their hand and the rubber hand as significantly more similar than participants who had not experienced the illusion. That is, embodiment leads to perceived similarity, but perceived similarity does not lead to embodiment. Furthermore, similarity ratings following the illusion were selectively correlated with some components of embodiment, but not with others. These results suggest an important role of a mental body image in the perception of the relation between the self and others.