Brand & Yancey1993’s Pain: The Gift No One Wants, pg191–197, recounts Brand’s research in the 1960s–1970s in attempting to create “artificial pain” or “pain prosthetics”, which ultimately failed because human perception of pain is marvelously accurate & superior to the crude electronics of the day, but more fundamentally because they discovered the aversiveness of pain was critical to accomplishing the goal of discouraging repetitive or severely-damaging behavior, as the test subjects would simply ignore or disable the devices to get on with whatever they were doing.

…The first question—Why must pain be unpleasant?—I knew the answer to, an answer that underlay my entire approach to pain. The very unpleasantness of pain, the part we hate, is what makes it so effective at protecting us. I knew that answer theoretically, but the debilitating effect of pain on patients sometimes made me wonder. A related question followed: Why must pain persist? Surely we would better appreciate pain if our bodies came equipped with an on-off feature, allowing us to switch off the warning at will.

My grant application bore the title “A Practical Substitute for Pain”. We proposed developing an artificial pain system to replace the defective system in people who suffered from leprosy, congenital painlessness, diabetic neuropathy, and other nerve disorders. Our proposal stressed the potential economic benefits: by investing a million dollars to find a way to alert such patients to the worst dangers, the government might save many millions in clinical treatment, amputations, and rehabilitation.

The proposal caused a stir at the National Institutes of Health in Washington. They had received applications from scientists who wanted to diminish or abolish pain, but never from one who wished to create pain. Nevertheless, we received funding for the project.

We planned, in effect, to duplicate the human nervous system on a very small scale. We would need a substitute “nerve sensor” to generate signals at the extremity, a “nerve axon” or wiring system to convey the warning message, and a response device to inform the brain of the danger. Excitement grew in the Carville research laboratory. We were attempting something that, to our knowledge, had never been tried.

I subcontracted with the electrical engineering department at Louisiana State University to develop a miniature sensor for measuring temperature and pressure. One of the engineers there joked about the potential for profit: “If our idea works, we’ll have a pain system that warns of danger but doesn’t hurt. In other words, we’ll have the good parts of pain without the bad! Healthy people will demand these gadgets for themselves in place of their own pain systems. Who wouldn’t prefer a warning signal through a hearing aid over real pain in a finger?”

The LSU engineers soon showed us prototype transducers, slim metal disks smaller than a shirt button. Sufficient pressure on these transducers would alter their electrical resistance, triggering an electrical current. They asked our research team to determine what thresholds of pressure should be programmed into the miniature sensors. I replayed my university days in Tommy Lewis’s pain laboratory, with one big difference: now, instead of merely testing the in-built properties of a well-designed human body, I had to think like the designer. What dangers would that body face? How could I quantify those dangers in a way the sensors could measure?

To simplify matters, we focused on fingertips and the soles of feet, the two areas that caused our patients the most problems. But how could we get a mechanical sensor to distinguish between the acceptable pressure of, say, gripping a fork and the unacceptable pressure of gripping a piece of broken glass? How could we calibrate the stress level of ordinary walking and yet allow for the occasional extra stress of stepping off a curb or jumping over a puddle? Our project, which we had begun with such enthusiasm, seemed more and more daunting.

I remembered from student days that nerve cells change their perception of pain in accordance with the body’s needs. We say a finger feels tender: thousands of nerve cells in the damaged tissue automatically lower their threshold of pain to discourage us from using the finger. An infected finger seems as if it is always getting bumped—it “sticks out like a sore thumb”—because inflammation has made it 10× more sensitive to pain. No mechanical transducer could be so responsive to the needs of living tissue.

Every month the optimism level of the researchers went down a notch. Our Carville team, who had made the key findings about repetitive stress and constant stress, knew that the worst dangers came not from abnormal stresses, but from very normal stresses repeated thousands of times, as in the act of walking. And Sherman the pig [pg171–172; research on the pig involved paralyzing it & applying slight consistent pressure for 5–7h to spots, which was enough to trigger inflammation & kill hair on the spots.] had demonstrated that a constant pressure as low as one pound per square inch could cause skin damage. How could we possibly program all these variables into a miniature transducer? We would need a computer chip on every sensor just to keep track of changing vulnerability of tissues to damage from repetitive stress. We gained a new respect for the human body’s capacity to sort through such difficult options instantaneously.

After many compromises we settled on baseline pressures and temperatures to activate the sensors, and then designed a glove and a sock to incorporate several transducers. At last we could test our substitute pain system on actual patients. Now we ran into mechanical problems. The sensors, state-of-the-art electronic miniatures, tended to deteriorate from metal fatigue or corrosion after a few hundred uses. Short-circuits made them fire off false alarms, which aggravated our volunteer patients. Worse, the sensors cost about $2,237.53^$450₁₉₇₀ each and a leprosy patient who took a long walk around the hospital grounds could wear out a $9,944.56^$2,000₁₉₇₀ sock!

On average, a set of transducers held up to normal wear-and-tear for 1–2 weeks. We certainly could not afford to let a patient wear one of our expensive gloves for a task like raking leaves or pounding a hammer—the very activities we were trying to make safe. Before long the patients were worrying more about protecting our transducers, their supposed protectors, than about protecting themselves.

Even when the transducers worked correctly, the entire system was contingent on the free will of the patients. We had grandly talked of retaining “the good parts of pain without the bad”, which meant designing a warning system that would not hurt. First we tried a device like a hearing aid that would hum when the sensors were receiving normal pressures, buzz when they were in slight danger, and emit a piercing sound when they perceived an actual danger. But when a patient with a damaged hand turned a screwdriver too hard, and the loud warning signal went off, he would simply override it—This glove is always sending out false signals—and turn the screwdriver anyway. Blinking lights failed for the same reason.

Patients who perceived “pain” only in the abstract could not be persuaded to trust the artificial sensors. Or they became bored with the signals and ignored them. The sobering realization dawned on us that unless we built in a quality of compulsion, our substitute system would never work. Being alerted to the danger was not enough; our patients had to be forced to respond. Professor Eugene Tims of LSU said to me, almost in despair, “Paul, it’s no use. We’ll never be able to protect these limbs unless the signal really hurts. Surely there must be some way to hurt your patients enough to make them pay attention.”

We tried every alternative before resorting to pain, and finally concluded Tims was right: the stimulus had to be unpleasant, just as pain is unpleasant. One of Tims’s graduate students developed a small battery-operated coil that, when activated, sent out an electric shock at high voltage but low current. It was harmless but painful, at least when applied to parts of the body that could feel pain.

Leprosy bacilli, favoring the cooler parts of the body, usually left warm regions such as the armpit undisturbed, and so we began taping the electric coil to patients’ armpits for our tests. Some volunteers dropped out of the program, but a few brave ones stayed on. I noticed, though, that they viewed pain from our artificial sensors in a different way than pain from natural sources. They tended to see the electric shocks as punishment for breaking rules, not as messages from an endangered body part. They responded with resentment, not an instinct of self-preservation, because our artificial system had no innate link to their sense of self. How could it, when they felt a jolt in the armpit for something happening to the hand?

I learned a fundamental distinction: a person who never feels pain is task-oriented, whereas a person who has an intact pain system is self-oriented. The painless person may know by a signal that a certain action is harmful, but if he really wants to, he does it anyway. The pain-sensitive person, no matter how much he wants to do something, will stop for pain, because deep in his psyche he knows that preserving his own self is more important than anything he might want to do.

Our project went through many stages, consuming 5 years of laboratory research, thousands of man-hours, and more than a million dollars of government funds. In the end we had to abandon the entire scheme. A warning system suitable for just one hand was exorbitantly expensive, subject to frequent mechanical breakdown, and hopelessly inadequate to interpret the profusion of sensations that constitute touch and pain. Most important, we found no way around the fundamental weakness in our system: it remained under the patient’s control. If the patient did not want to heed the warnings from our sensors, he could always find a way to bypass the whole system. [cf. Pavlok]

Looking back, I can point to a single instant when I knew for certain that the substitute pain project would not succeed. I was looking for a tool in the manual arts workshop when Charles, one of our volunteer patients, came in to replace a gasket on a motorcycle engine. He wheeled the bike across the concrete floor, kicked down the kickstand, and set to work on the gasoline engine. I watched him out of the corner of my eye. Charles was one of our most conscientious volunteers, and I was eager to see how the artificial pain sensors on his glove would perform.

One of the engine bolts had apparently rusted, and Charles made several attempts to loosen it with a wrench. It did not give. I saw him put some force behind the wrench, and then stop abruptly, jerking backward. The electric coil must have jolted him. (I could never avoid wincing when I saw our man-made pain system function as it was designed to do.) Charles studied the situation for a moment, then reached up under his armpit and disconnected a wire. He forced the bolt loose with a big wrench, put his hand in his shirt again, and reconnected the wire. It was then that I knew we had failed. Any system that allowed our patients freedom of choice was doomed.

I never fulfilled my dream of “a practical substitute for pain”, but the process did at last set to rest the two questions that had long haunted me. Why must pain be unpleasant? Why must pain persist? Our system failed for the precise reason that we could not effectively reproduce those two qualities of pain. The mysterious power of the human brain can force a person to STOP!—something I could never accomplish with my substitute system. And “natural” pain will persist as long as danger threatens, whether we want it to or not; unlike my substitute system, it cannot be switched off.

As I worked on the substitute system, I sometimes thought of my rheumatoid arthritis patients, who yearned for just the sort of on-off switch we were installing. If rheumatoid patients had a switch or a wire they could disconnect, most would destroy their hands in days or weeks. How fortunate, I thought, that for most of us the pain switch will always remain out of reach.