A placebo is a medial intervention that can product a placebo effect. placebos depend on the controlled and measured use of deception, by means of inert tablets, 'fake' surgeries and other procedures based on false information. For example, a patient may be given an inert pill, but not told that it is inert. This may cause the patient to believe the treatment will change his/her condition and this will create a subjective perception of a treatment effect, when in fact it is a placebo effect.

Placebos are widely used in research and the now well-known placebo effect is a pervasive phenomenon. It points to the importance of perception and the brain's significant role in physical health.