Subject-expectancy effect

In scientific research and psychotherapy, the subject-expectancy effect, is a form of reactivity that occurs when a research subject expects a given result and therefore unconsciously affects the outcome, or reports the expected result. Because this effect can significantly bias the results of experiments (especially on human subjects), double-blind methodology is used to eliminate the effect.

Like the observer-expectancy effect, it is often a cause of "odd" results in many experiments. The subject-expectancy effect is most commonly found in medicine, where it can result in the subject experiencing the placebo effect or nocebo effect, depending on how the influence pans out.