What is a Placebo? - Definition & Explanation Video

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  • 0:00 What Is a Placebo?
  • 0:48 How Placebos Are Used
  • 1:11 Placebos and Blind Trials
  • 2:14 An Example Placebo Study
  • 3:16 Lesson Summary
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Lesson Transcript
Instructor: Lisa Roundy

Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.

A placebo is something given to a person that has no physical effect on that person, even though they may think that it does. In this lesson, you will discover why placebos are used and their purpose in an experiment.

What Is a Placebo?

You see a little boy running on a playground. He falls down and starts to cry. Then, he runs over to his mother. As far as you can tell, there's no scrape or cut where the little boy fell down, but even so, his mom puts a bandage on the child's knee. The child stops crying immediately and resumes his play.

Band-Aid on Child

The bandage didn't actually heal the little boys knee, right? So, what happened to make him feel better? You've just seen the child receive a placebo, something given to a person with a complaint that has no real physical effect on that person.

The placebo in this case is the bandage. It actually makes the child feel better, even though there is no medical reason that it should do so. This is an example of the placebo effect. The placebo effect occurs when someone receiving a placebo but who incorrectly believes they are receiving real treatment reports an improvement in their condition.

How Placebos Are Used

The use of placebos originated when physicians discovered that giving sugar pills to patients could have surprisingly good results. Imagine a patient who complains of being tired, even though there is no evidence she is actually sick. The doctor knows the patient wants treatment, so he gives the patient a pill containing no medication. That's our placebo. In some cases, it relieves the symptoms thanks to the placebo effect.

Placebos and Blind Trials

Placebos were commonly used in general medicine until the 20th century. Today, the use of a placebo by your doctor would be considered dishonest and unethical, but they are commonly used in studies that test the effectiveness of true medical treatments. Placebos are often used to create blind trials.

Many studies break participants down into two groups: One group is given the medicine or treatment being tested, and the other group is not. In a blind trial the participants are not aware of which group they are assigned to. The second group receives a placebo, so every participant takes something, which may or may not be the tested medicine. Only the researchers know who gets the real treatment and who gets a placebo. In other words, the participants are 'blind' to their situation.

They are also used in double blind trials. A double blind trial is similar to a blind trial but neither the researcher nor the participant knows who is assigned to which group. This helps eliminate the possibility of bias due to the researcher's perceptions. Using a placebo is not the only method for creating these types of studies, but it is a very common and important method.

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