The subject-expectancy effect
When people know what the result of taking a pill is supposed to be, they might unconsciously change their reaction to cause that result or report that result has taken place even if it hasn't.
However, studies show that a placebo doesn't trick the brain - the brain reacts differently to a drug than a placebo. A 2004 study showed that the expectation of pain relief causes the brain's relief system to activate.
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