The phantom head.

A student volunteer was asked to stand just behind a mannequin so that the student was looking at the back of the mannequin's plastic head. The experimenter stood off to one side and used her two hands to stroke and tap the back of the student's head in perfect synchrony with the back of the mannequin's head. After 1-2 min the majority of naive subjects tested began experiencing the sensations as emerging from the mannequin's head rather than from their own, demonstrating a novel 'phantom-head' illusion. The fact that sensory referral here occurs to a part of the body that is not normally visually accessible challenges the leading Hebbian explanation of the well-studied rubber-hand illusion.