The Placebo Effect: The Power of Expectation


How do you know if a drug or medication works? In an experiment, you usually have an experimental group and a control group. However, when testing out a new drug, if you only have a treatment group and a no-treatment group, you might not yield authentic results. This is because the treatment group expects their condition to improve, while the no-treatment group does not. Is expectation really that powerful though? Could anticipation alone lead to the same benefits that the drug is supposed to bring about? And how could this be tested?


The answer lies in something called a placebo. A placebo is a fake treatment used as a neutral substitute for the real drug, such as a sugar pill. Its most important characteristic is that it does not contain any quality that would promote physiological improvement. So when we want to test the effectiveness of a new medicine, we assign one group the treatment and another group the placebo, making them the experimental group and placebo group, respectively. For many studies, the placebo group is a replacement for the control group. The placebo group’s improvements, which are based solely on their expectations that the “treatment” is going to work, can be compared with that of the treatment group. The difference between the changes in the two groups represents the improvement caused by the treatment itself.

The Placebo Effect

The placebo effect occurs when a person who is given an ineffective treatment still shows improvement simply based on their expectation of the treatment’s effectiveness.

The History

The term “placebo effect” was not introduced until the 1920s, but people were certainly aware of the concept much earlier than that. Michel de Montaigne, a French philosopher, was the first one to mention a phenomenon similar to the placebo effect in the middle of the 16th century. He said, “There are men on whom the mere sight of medicine is operative.” He witnessed treatments of the day, such as healing potions and pills, that only seemed to work when people believed they would. Their expectations legitimately caused real physiological benefits. 

Much later, in 1799, the placebo effect was first demonstrated in an experiment by John Haygarth. He was a British philosopher who was skeptical about a newly developed medical treatment called a Perkins tractor, which was a large metal rod meant to draw disease out of the body. Haygarth decided that the best way to see if the Perkins tractor actually worked or not was to construct a wooden sham version that looked exactly like a Perkins tractor. Haygarth distributed his fake Perkins tractor to people who had various pain in their joints or connective tissue, and 4 of 5 patients reported that their pain had improved after using the fakes. Although Haygarth did not use the term “placebo effect” to define his results, his experiment made it clear that expectation can play a legitimate role in physiological symptoms. Haygarth concluded that just because a treatment seems to work does not mean the treatment itself is effective; it might just be the patient’s expectation to heal that heals them.

So What

The placebo effect is still used when testing treatments in the present day. Thus, the placebo effect has had a tremendous impact on the accuracy of the medical field as a whole, and it is a crucial element of modern medicine. However, the placebo effect is not always positive. Sometimes, when people are told that they may experience negative side effects like headache and nausea, they end up experiencing these adverse side effects even when they take the placebo treatment due to expectation.

Additionally, the placebo effect extends further than just medicine. There are lots of everyday placebos. These include fake crosswalk buttons and fake elevator door close buttons. The functions of each usually run on a timer. Thus, pushing the button eventually leads to the desired function, but the button and the result are not connected in any way. The button is a sham, yet people believe they are causing the light to change or the door to close. The idea of these “dummy buttons” is that people think they have more control than they do, so it makes them feel better about the situation. Is the benefit of having an automated system worth the deception? For many business owners, the answer is yes. For example, it’s more cost-effective to put crosswalk lights on a timer than to connect each one to the system that controls traffic lights. Meanwhile, a hotel owner can save money on an automated elevator while also preserving guests’ happiness by giving them a false sense of power. Ultimately, everyone likes to feel in control, and these modern-day placebos, though deceptive, preserve that feeling.

The placebo effect is a testament to the power of expectation. This potential is why having an optimistic attitude can be so beneficial. If you believe something will happen, then chances are, it will.

Think Further

  1. What are some potential drawbacks of testing a new drug without having a placebo group?
  2. Do you see any issues with modern placebos like fake crosswalk buttons? Do the benefits outweigh the psychological costs?
  3. Can you identify any experiences from your life in which your anticipation brought about the outcome (whether positive or negative)?


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Learn More

  1. Price, Eleanor. “The White Lies of Everyday Placebos.” The Prindle Post, 8 Aug. 2017,
  2. DerSarkissian, Carol. “The Placebo Effect: What Is It?” WebMD, WebMD, 8 Feb. 2020,
  3. Mestel, Rosie. “The Imagination Effect: A History of Placebo Power.” Knowable Magazine | Annual Reviews, Annual Reviews, 25 Oct. 2017,