Because pain is impossible to precisely measure or quantify, it remained poorly understood for many years. Well into the 20th century, doctors struggled to provide appropriate amounts of medication or anesthesia to patients experiencing traumalike injury, surgery or childbirth. Unfortunately, this lack of understanding led some doctors to test some pretty wacky theories.
One of the most infamous efforts to objectively measure pain occurred at New York Hospital in 1948. Two doctors, James Hardy and Carl Javert, fashioned a device called a dolorimeter, which literally means a "measure of pain," and connected it to a heat gun. Then they enlisted the assistance of 13 pregnant nurses or wives of doctors at the hospital. When the women went into labor, the physicians began applying heat of increasing intensity to the back of the ladies' hands in between contractions, asking them what intensity matched their pain. They used the resulting readings, given in "dols" (a pain unit they made up) to determine the level of pain experienced at a given length of time between contractions. Shockingly, one woman took the experiment so far that she received second-degree burns, maxing out the dolorimeter at 10.5 dols! Unfortunately for Hardy and Javert, not to mention the woman who was badly burned, their pain scale couldn't be reproduced by other doctors and, as a result, never caught on [sources: Hardy and Javert, RadioLab].
Meanwhile, other doctors were experimenting under a different assumption that now seems obvious: Pain is an experience that is best described by the person experiencing it. The same year Hardy and Javert were burning hands, cardiologist Kenneth Keele created an early pain scale in which patients were simply asked to rank their current pain as "0" for none, "1" for mild, "2" for moderate or "3" for severe. In 1964 a group of English psychiatrists devised a scale consisting of a 4-inch (10-centimeter) line with the words "no pain" on one side and "the pain is as much as I can bear" on the other. Then, beginning in the 1970s, the number of pain scales swelled, giving doctors today dozens from which to choose [source: Noble et al.].