If only all people with phantom-limb syndrome felt such pleasurable sensations. Unfortunately, amputees often experience excruciating phantom pain in their missing body parts. Even those who may not have chronic pain can sometimes "feel" pain when it's seemingly induced in the phantom limb, as Ramachandran discovered.
I didn't realize how compelling these felt movements could be until I met John McGrath, an arm amputee who telephoned me after he had seen a television news story on phantom limbs. An accomplished amateur athlete, John had lost his left arm just below the elbow three years earlier. "When I play tennis," he said, "my phantom will do what it's supposed to do. It'll want to throw the ball up when I serve or it will try to give me balance in a hard shot. It's always trying to grab the phone. It even waves for the check in restaurants," he said with a laugh.
John had what is known as a telescoped phantom hand. It felt as if it were attached directly to his stump with no arm in between. However, if an object such as a teacup were placed a foot or two away from the stump, he could try to reach for it. When he did this, his phantom no longer remained attached to his stump but felt as if it were zooming out to grab the cup.
On a whim I started thinking, What if I ask John to reach out and grab this cup but pull it away from him before he "touches" it with his phantom? Will the phantom stretch out, like a cartoon character's rubbery arm, or will it stop at a natural arm's length? How far can I move the cup away before John will say he can't reach it? Could he grab the moon? Or will the physical limitations that apply to a real arm also apply to the phantom?
I placed a coffee cup in front of John and asked him to grab it. Just as he said he was reaching out, I yanked away the cup.
"Ow!" he yelled. "Don't do that!"
"What's the matter?"
"Don't do that," he repeated. "I had just got my fingers around the cup handle when you pulled it. That really hurts!"
Hold on a minute. I wrench a real cup from phantom fingers and the person yells, ouch! The fingers were illusory, of course, but the pain was real—indeed, so intense that I dared not repeat the experiment.