ABX Double Blind Testing

ABX Home ABX Books ABX Periodical ABX Publications

What's the Placebo Effect?

What is the Placebo Effect? - by David Carlstrom
A placebo is an ineffective treatment given in a controlled study as a reference.
In one of the first large scale double blind tests done in medicine, the test of the Salk Polio vaccine, half the test subject children were given injections of the Salk vaccine and the other half were given sterile injectable saline, a salt solution with the same percentage of salt as normal body fluids. Because the Salk vaccine was slightly pink, the placebo saline was tinted pink. That is the placebo was a treatment that looked like the real thing, but when injected would have no effect at all. The test was evaluated by comparing the reduction in polio cases in the group receiving the Salk vaccine to the group receiving saline. What could be simpler than comparing something that might work with something that doesn't work. No one had to explain this procedure more than once to the elementary school children who were the test subjects.
But an adult may ask why use the placebo at all? If it does nothing why not just compare the test group with the historical rate of polio cases? The problem is the historical rate of polio varied a lot. No one could prove why the rate changed, but they knew it did. In some summers there were far more cases than in other years. The placebo was used so the groups of children were tested in the same season under all the same conditions. Whatever the conditions enhancing or inhibiting polio in some years were, they would at least be the same for both test groups.
Why inject the children with pink saline? Why not just make a list of the untreated children's names? This is the interesting question! In this kind of test, it has been found that both test groups do better than would be expected. This seems to be because if a doctor treats someone they tend to feel better, whether the doctor gives any medicine or not.
No one knows why this is true, although there is a lot of speculation. The point is that it does happen and to test a new drug, it has to be eliminated to be sure the test results are real.
In summary placebos are used because it is normal for people to feel better when treated by a healer whether or not the healer gives effective medicine or snake oil. This fact of feeling better when treated with or without an effective treatment is called the placebo effect. That is the placebo effect is the fact that people feel better even when given a treatment that does nothing.
No one knows why this is true, but we have proof that it happens. I emphasize this because critics often try to respond to the many theories of what might cause the placebo effect. We don't know what causes it, but we do have solid proof that it does happen.
In comparing audio components the same thing happens. A new component will usually sound different from the old component. This holds true even when the component is identical, as when a trick comparison is done of one component with itself. Here too, no one knows why it happens, but there is proof that it does.
Just as the placebo effect is removed from a drug test by a double blind procedure, we can remove it from an audio comparison by preventing the listener from knowing which component is which.
With this control, it becomes much harder for the listener to tell which component he is listening to. But if he hears a difference, we can be sure it is a real difference, not an auditory placebo effect.
Audiophiles are often shocked and offended by how much change there is in their "ability" to hear sonic differences when a comparison is done with a double blind protocol. They try to blame the slightest detail of the test equipment or procedure rather than realize that the blind test result is reliable and their previous experiences were tainted by the placebo effect.
In conclusion, in any audio comparison look out for the placebo effect. Who wants to spend money for a new component because it sounds better only to find out later that there is no difference in the sound quality? If you are buying a new audio component you want to be sure you are getting a worthwhile change not just a warm feeling from the newness of it. Of course if you like to spend money and feel good about it, you have the right to do that. The results of careful double blind comparisons are for those who want the best, but have less than infinite funds, and like to get value for their money, along with those who are interested in understanding the nature of human responses.

ABX Home ABX Books ABX Periodical ABX Publications
Send questions or comments on the ABX Web Page to David Carlstrom.

Web Page Created by David Carlstrom. Last Modified: 1/26/2011