now the next question is, what can you learn about phantom limbs by doing experiments? One of the things we've found was, about half the patients with phantom limbs claim that they can move the phantom. It'll pat his brother on the shoulder, it'll answer the phone when it rings, it'll wave goodbye. These are very compelling, vivid sensations. The patient's not delusional. He knows that the arm is not there, but, nevertheless, it's a compelling sensory experience for the patient. But however, about half the patients, this doesn't happen. The phantom limb -- they'll say, "But doctor, the phantom limb is paralyzed. It's fixed in a clenched spasm and it's excruciatingly painful. If only I could move it, maybe the pain will be relieved.