Suppose I want to improve performance of my washing machine. Ways I might do this fall into three categories:
1. Supply missing inputs. It needs water, soap, and electricity. If any one of them is missing, I can greatly improve performance by adding it — by plugging the machine in, for example. These changes are easy because water, soap, and electricity are easy to get.
2. Replace broken parts. This will also greatly improve performance. These changes are very difficult unless I am a washing machine repairman.
3. Everything else. To improve performance any other way will be difficult and any improvements will be small. These other methods of improvement — such as putting special disks into the wash — are also likely to be dangerous.
All complex machines are like this. What I call the Washing Machine Principle says that humans are also like this. This means that non-transplant attempts to improve human well-being fall into two clusters: 1. Easy, safe, and highly effective. 2. Difficult, dangerous, and only slightly effective.
Some simple examples:
- Vitamins. If you have a deficiency disease, getting more of the right vitamin will cure you easily, safely, and rapidly. They supply a missing input.
- Antidepressants. They are dangerous, difficult to make and obtain, and don’t work very well. In controlled studies, they do only slightly better than placebos. Patients typically must try several to find one that works. They don’t supply a missing input.
- The mirror treatment for certain neurological conditions that Atul Gawande recently described:
[The patient's] left hand felt cartoonishly largeâ€”at least twice its actual size. He developed a constant burning pain along an inch-wide ribbon extending from the left side of his neck all the way down his arm. And an itch crept up and down along the same band, which no amount of scratching would relieve. . . . [These symptoms had lasted 11 years. Gawande suggested trying the mirror treatment.] After a couple of weeks, his hand returned to feeling normal in size all day long. The mirror also provided the first effective treatment he has had for the flares of itch and pain.
The mirror treatment is cheap, safe, and, in this case, highly effective. Clearly it supplies a missing input.
To be continued.