The territory of my body: Testosterone prevents limb cooling in the Rubber Hand Illusion
The Rubber Hand Illusion (RHI) is an experimental paradigm for assessing changes in body ownership. Recent findings in the field suggest that social-emotional variables can influence such changes. Since body ownership is a mechanism that enables subjects to organise information about the environment and interact efficiently in it, changes in body ownership should have important implications for social power. In the current study, we investigated whether 0.5mg of testosterone, a steroid hormone strongly implicated in the achievement of power and dominance, affected the RHI. Forty-nine females participated in a double-blind, placebo-controlled experiment in which the RHI was induced. Compared to placebo, testosterone had no effects on the usual alteration of subjective ownership over the rubber limb or on subjective sense of proprioceptive drift. However, unlike the placebo group, testosterone-treated participants did not display an objective decline in the temperature of their own (hidden) hand following induction of the illusion. These findings suggest that testosterone strengthens implicit but not explicit bodily self-representations. We propose that effective maintenance of implicit body boundaries can be regarded, conceptually, as a primary defensive state facilitating integrity of the self.