To Study OCD, Scientists Get Their (Rubber) Hands Dirty

The rubber hand illusion is a classic experiment that reveals how our brains build a sense of our bodies. For the latest twist on the illusion, researchers simulated OCD-like feelings of disgust in subjects by starting with rubber hands and adding fake blood, vomit and feces. The basic rubber hand experiment is simple to set up. It requires a fake hand, two paintbrushes, a table, and something to use as a little wall. A subject sits with both hands flat on the table, one of them farther out to the side. The barrier blocks her view of that hand. The rubber hand lies just inside the wall, so that when the subject looks down she sees two hands in front of her—but only one is her own. Across the table, an experimenter uses the two brushes to stroke the backs of the hidden hand and the rubber hand at the ...