The placebo effect is a real phenomenon, first identified in the 1950s and studied ever since, with sometimes surprising results. Take, for example, a 2008 study conducted by a team led by Dan Ariely, a behavioral economist at Duke University. Ariely and company gathered 82 people and gave them electric shocks in their wrists. Then, each of the test subjects were given one of two pills, shocked again, and asked to compare the pre-pill pain to the post-pill discomfort. Of the first group, 85% said the pill reduced the pain. On the other hand, only 61% of the second group said that the pill did its job. Whatever the researchers gave their "patients" worked -- but the first pill clearly worked better.
It shouldn't surprise you that some of these test subjects received placebos. That, however, is not the case. All of the test subjects received placebos, and on top of that, both groups received the exact thing -- sugar pills of identical size, shape, etc. So why did the first group feel less pain than the second?
SEE the answer at Now I Know.