Can You Rule Out Placebo Effect?

I wrote this page for students who have given arguments analogous to the following.

"I know that witch-doctoring works because I have personal experience of being cured by a witch-doctor. I had severe elbow pain for three weeks, which seriously cut into my drinking. Then I went to a witch-doctor and he threatened my elbow with a big stick to scare out the pain-demons who had taken up residence there. Afterwards, I felt better, so I know that witch-doctoring works."

The trouble with such reasoning is that the "cure" could easily be due to placebo effect. Placebo effect is when someone gets some treatment that he thinks will make him feel better, and therefore feels better, whether or not the "treatment" had any real effect at all. Sugar pills can cure headaches if the recipients think they're getting asprin, and so on.

For this reason all new medications are tested against placebo. Half the people in any study get a placebo, (an inert pill) that they're told is the medicine. If the real medicine doesn't do any better than the placebo then we should conclude that it doesn't work at all, because the extent that it seems to work can be explained by placebo effect.

So the question is, can you rule out placebo effect as the cause of the improvement you think you got from visiting a witch doctor, a chiropractor, a psychic surgeon, an aromatherapist, a crystal healing dude or whatever?

Copyright © 2005 by Martin C. Young

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