Self-perception beyond the body: the role of past agency.

Technological progress provides us with an increasing variety of devices that now mediate what previously has been achieved by social face-to-face interaction. Here, we investigate whether this leads to the incorporation of such devices into representations of our body. Using explicit (body ownership questionnaire) and implicit (proprioceptive drift rate) measures together with a synchronous/asynchronous stroking technique, we show that people have an increased tendency to integrate non-corporeal objects into their body after synchronous stroking. Explicit measures of body ownership show that people had greater average scores in the synchronous condition as compared to the asynchronous condition for all objects that we tested (computer mouse, rubber hand, smart phone, and a wooden block). However, our implicit measure of body ownership showed a numerically larger proprioceptive drift for a rubber hand than for a computer mouse, numerically comparable ownership measures for a smart phone and a rubber hand, and a significantly stronger proprioceptive drift for a smart phone than for a wooden block. These findings suggest that direct, subjective measures and indirect, objective measures of body ownership are based on different kinds of information; the latter might be more sensitive to objects for which we recall past agency based on our history of personal experiences with these objects. Taken altogether, our observations support the idea that the perceived bodily self is rather flexible and is likely to emerge through multisensory integration and top-down expectations of agency.