Haptic perception after a change in hand size.

When we actively explore with our hands (haptics), the brain must combine diverse sensory signals into a unified percept. Presumably, a key role is played by an internal model of the body, but the processes responsible for forming and maintaining such a model are poorly understood. We used a multisensory illusion to alter the internal model of one's hand by using fake hands smaller or larger than the participant's hand. After such brief illusion we observed a change in haptically perceived object size. These results demonstrate that the brain rapidly recalibrates haptic signals using an internal model of the hand and that this model is multisensory rather than merely visual or memory-based.