Despite decades of research, doctors have few tools to measure pain objectively. Generally, they ask patients to rate it themselves from one to 10, or point to the cartoon face on the wall chart whose expression best matches how they feel. "We don't have a pain-o-meter," says Joel Saper, MD, director of the Michigan Head Pain and Neurological Institute in Ann Arbor, which draws about 10,000 patients a year, including some of the nation's toughest migraine cases. Saper estimates that 15% to 20% of them are faking—or at least, aren't as incapacitated as they say. Some are dependent on painkillers or seeking to resell them, he says. Some want a doctor to certify that they'll never be able to work again and deserve disability payments. Some, he thinks, don't really want to get well because they subconsciously find power in their pain.