Placebo comes from the Latin word meaning “I shall please.” It is a substance with no active therapeutic effect. A placebo is given to a person in order to deceive them into thinking that it is an active treatment. In drug testing, a placebo can be made to resemble an active medication so that it functions as a control; this is to prevent the recipient from knowing whether a treatment is active or inactive. This psychological phenomenon, in which the recipient perceives an improvement in condition due to personal expectations, rather than the treatment itself, is known as the placebo effect. The placebo effect points to the importance of perception and the brain's role in physical health.