Rubber hand illusions and size-weight illusions: self-representation modulates representation of external objects.

Bodily illusions offer an experimental method to investigate the origins and functional role of the sense of one's own body. Using the rubber hand illusion (RHI) we show that a representation of one's own body is implicitly used to calibrate perception of external objects. Twelve participants experienced the RHI while watching stimulation of a large or small glove simultaneously with stimulation of their own hand. They then grasped cylinders of identical size but varying weight. RHI with the large glove caused the cylinders to feel heavier. We suggest that an illusory increase in hand size made the subsequently grasped cylinder feel correspondingly small, evoking a size-weight illusion. Self-representation thus influenced exteroception. The sense of one's own body provides a fundamental reference for perception in general.