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Experimental Psychology

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Placebos in Research


Source: Laboratories of Gary Lewandowski, Dave Strohmetz, and Natalie Ciarocco—Monmouth University

Clinical research focuses on the efficacy of treatments for addressing disorders and illnesses. A challenge with this type of research is that participants often have pre-existing beliefs about the treatment, particularly expectations that the treatment will work.

Though it has been practiced around the world for centuries, yoga is a relatively recent fitness craze in the United States with a wide range of alleged benefits, including the belief that it improves one’s creativity. However, it is not always clear whether yoga is actually creating the benefits, like improved creativity, or the yoga practitioner’s expectations are really the cause.

This video demonstrates a two-group design that examines whether a person who believes he or she is doing yoga (but in reality is not) experiences similar benefits to a person who actually does yoga. Specifically, this study looks at whether there is a placebo effect such that merely believing you are doing yoga benefits creativity. 

Psychological studies often use higher sample sizes than studies in other sciences. A large number of participants helps to ensure that the population under study is better represented and the margin of error accompanied by studying human behavior is sufficiently accounted for. Further, human participants for research like this are often readily available and the experiment is quick and inexpensive to replicate. In this video we demonstrate this experiment using just one participant. However, as represented in the results, we used a total of 80 (40 for each condition) participants to reach the experiment’s conclusions.


1. Define key variables.

  1. Create an operational definition (i.e., a clear description of exactly what a researcher means by a concept) of yoga-related beliefs.
    1. For the purposes of this experiment, a yoga-related belief is the activation of a participant’s preconceived notions about yoga and its potential benefits that will be manipulated by having the participant do a series of basic stretches that he or she is told is yoga.
  2. Create an operational definition (i.e., a clear description of exactly what a researcher means by a concept) of creativity.
    1. For purposes of this experiment, creativity is defined as the number of alternative uses a participant thinks of for a clothespin.

2. Conduct the study.

  1. Meet the student/participant at the lab.
  2. Provide participant with informed consent, a brief description of the research (Yoga and creativity), a sense of the procedure, an indication of potential risks/benefits, the right of withdrawal at any time, and a manner to get help if they experience discomfort.
  3. Run the placebo yoga condition.
    1. A placebo is an inert substance or procedure that a person believes has an active ingredient. Placebos test how much the mere belief that something works can produce changes in the dependent variable.
    2. Tell the participant: “In consultation with the wellness center at a local hospital we are testing the potential benefits of yoga. As you may know, yoga is a 5,000 year-old system of exercises and stretches designed to help build and emphasize connections between body and mind. For this study I’d like you to engage in a series of yoga movements.”
    3. Direct the participant to do several “yoga” stretches (these stretches are not actually considered yoga). Each stretch should be held for one minute.
  4. Run the stretching condition (shown with a different participant).
    1. Tell the participant: “In consultation with the wellness center at the local hospital, we are testing potential benefits of stretching. As you may know, stretching is an integral component to personal fitness. For this study I’d like you to engage in a series of stretching movements.”
    2. Instruct the participant do several stretches. Hold stretch should be held for one minute.
      1. These are purposefully the same as the placebo condition. Everything with the stretching condition should be the same with the exception of the introductory comments to the participant (2.3.2. and 2.4.1.).
  5. Give the participant the dependent variable.
    1. Give the participant the Guilford Alternative Uses Task1 by asking him or her to “list as many possible uses as you can think of in the next 3 minutes for a clothespin.”
    2. Give participant a piece of paper with numbered lines to fill in their answers.
      1. See a sample list from a participant (Figure 1).
        Figure 1
        Figure 1: Sample list of creative uses for a clothespin.
    3. Give participant the open-ended follow-up question about their perception of yoga. For example, what effects (if any) do you think yoga has on the mind and body? Make sure the participant indicates that yoga relates to physical and mental benefits including creativity/open-mindedness.

3. Debrief the participant.

  1.  Tell the participant the nature of the study.
    1. “Thank you for participating. In this study I was trying to determine that if a person simply believes he or she is doing yoga, it would it have the same benefits as actually doing yoga. There were two conditions, each comprising a series of basic stretches. However, one group thought they were doing yoga, while the other group knew they were basic stretches. We hypothesized that the group who thought they were doing yoga would generate a greater number of creative uses for the clothespin compared to the group who knew they were doing basic stretches.”
  2. Explain explicitly why deception was necessary for the experiment.
    1. “We want to tell you about the deception we used in this study. We used deception by telling participants we were testing these physical movements in conjunction with a local wellness center. That wasn’t true. We also told some participants they were doing yoga when in reality everyone did a series of basic stretches. We did this to test whether expectations about yoga’s benefits was enough to boost creativity. Deception was necessary because we wanted to get participants natural reaction. If participants were to know the true reasoning and hypothesis behind the study they may have performed in an unnatural way by trying to purposefully disprove the experimenter’s hypothesis. Because of the nature of the deception, it is quite natural for participants to not realize that they were being deceived.”

Placebos are widely included in clinical research and play an important role in therapeutic interventions. While clinical research relies on the efficacy of therapeutics for treating many disorders and illnesses, participants often have preexisting thoughts that can influence the outcome of drug trials. Such beliefs are referred to as placebo effects. The placebo effect points to the importance of perception and a psychological role in physical health. For example, the recent rise in the popularity of yoga as a fitness routine in Western countries has led to widespread beliefs regarding its benefits on health and wellness, including the idea that yoga enhances creativity. Through a unique experimental design, this video demonstrates how to design, perform, analyze, and interpret placebo responses. Here, the study examines whether a participant’s beliefs that yoga enhances creativity influences their creativity by listing alternative uses for a clothespin after stretching.

This placebo experiment incorporates a two-group design, a placebo and stretching group. In this case, the experiment is designed to highlight the placebo effect and should not be considered a control group, as it would be in other experiments. The two groups undergo the same series of stretching exercises. The placebo group is led to believe that they are going to engage in a series of yoga movements, whereas, the stretching group is led to believe that stretching is a critical component to personal fitness, with no mention of yoga. Note: the only difference is in the instructions given to the participant and no actual yoga is performed. After stretching, the participants are asked to list alternative uses for a clothespin. This dependent measure is interpreted as creativity. Participants who believe that doing Yoga leads to enhanced creativity should display a stronger placebo response than those who do not.

To setup the experiment, you will need: informed consent paperwork, copies of the initial research description and goals, a blank, lined piece of paper, writing pen, a clothespin, and copies of the final nature of the study for debriefing. To begin the experiment, meet the participant in the lab and explain the experimental guidelines. Guide all participants through the consent process, brief them with a description of the research on yoga and creativity, and discuss the overall plan for the session, including the potential risks and benefits. Assign this participant to the placebo yoga condition. Influence the participant that he or she is about to engage in a series of yoga movements. Remember that participants are not doing actual yoga movements, just stretching. Once the participant has been persuaded with the intent of yoga, direct him or her to do several “yoga” stretches and hold them for 1 min. Let the participant know that he or she can withdrawal at any time and ask for help if they experience discomfort. While the other participant is stretching, bring a different subject into the laboratory and assign them to the other experimental group, the stretching condition. After the participant has consented to the experiment, convey the message that the benefits of stretching are being tested. Now instruct the participant do several stretches and hold them for 1 min. Note that these are purposefully the same stretches as in the placebo condition. In a different room immediately after the stretching exercises, give participants a piece of paper with numbered lines and a pen. Ask the participant to list as many possible uses as you can think of in the next 3 min for a clothespin. Once the 3 min task is finished, ask the participant about their perception of yoga as it relates to physical and mental benefits including creativity and open-mindedness. At the conclusion of the experiment, debrief participants and explain why deception was necessary for the experiment.

The analysis of creativity after “yoga” stretching involves counting the number of ways participants listed to use clothespins. The data are then graphed by plotting the mean numbers for each condition to compare the placebo “belief in yoga” condition against the stretching condition. In this experiment, the placebo group listed more ways to creatively use clothespins than the stretching group.

Now that you have seen an experiment designed to uncover the extent of a placebo effect, let’s take a look at how researchers include placebo groups as important controls to study the effectiveness of medications. For example, in pharmacotherapy studies, subjects are unknowingly given a sugar pill—the placebo—and an active pill—the drug—and take them in random order. In many cases, medications are effective and produce beneficial effects on the measured outcome, as in this example where motor function was restored in patients with spinal cord injury after the administration of an anti-depressant drug compared to the placebo pill.

You’ve just watched JoVE’s introduction to placebos in research. Now you should have a good understanding of how to design and perform the experiment, as well as analyze results and apply the phenomenon. Thanks for watching! 

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80 participants were used (40 per condition in a different instance of this study conducted by the researchers). This large number of participants helps to ensure that the results reflect accurate mean numbers. If this research were conducted using just one or two participants, it is likely that the results would have been much different and not reflective of the greater population. The numbers reported reflect the mean number of creative uses for a clothespin participants in each condition listed (Figure 2).

After collecting data from 80 people, a t-test was performed for independent means to compare the placebo (belief in yoga) condition against the stretching condition. This simple two-group experiment shows how researchers use a placebo condition to test whether participants’ mere belief in a treatment’s effectiveness can influence outcomes on creativity.

Figure 2
Figure 2: Average number of creative clothespin uses by condition.

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Applications and Summary

The use of placebo conditions is particularly common in studies where researchers want to test a medication’s effectiveness. 

For example, DelBello and colleagues2 conducted a study of over 300 adolescents diagnosed with major depressive disorder. Researchers randomly assigned participants to either wear a patch (the selegiline transdermal system [STS] or EMSAM®) or to wear a placebo for 12 weeks. Compared to baseline measurement taken at week 1, both the treatment and placebo groups experienced similar reductions on their depression scores. This study demonstrates that those who simply believed they were receiving the treatment (i.e., the placebo group) experienced the same level of positive outcomes as those who received the actual treatment.  

Similarly, Del Re and colleagues3 conducted a meta-analysis of 47 alcohol pharmacotherapy studies. They found that placebo groups had significant improvement overall and that improvements were greater in more recent studies. Improvements were especially likely when the placebo was administered more frequently and when participants had more severe illnesses.

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  1. Guilford, J.P. The Nature of Human Intelligence. New York: McGraw Hill (1967).
  2. DelBello, M. P., Hochadel, T. J., Portland, K., Azzaro, A. J., Katic, A., Khan, A., & Emslie, G. A double-blind, placebo-controlled study of selegiline transdermal system in depressed adolescents. Journal of Child and Adolescent Psychopharmacology. 24 (6), 311-317. doi:10.1089/cap.2013.0138 (2014).
  3. Del Re, A. C., Maisel, N., Blodgett, J. C., Wilbourne, P., & Finney, J. W. Placebo group improvement in trials of pharmacotherapies for alcohol use disorders: A multivariate meta-analysis examining change over time. Journal of Clinical Psychopharmacology. 33(5), 649-657. doi:10.1097/JCP.0b013e3182983e73 (2013).



Placebos Clinical Research Therapeutic Interventions Drug Trials Placebo Effects Perception Psychological Role Physical Health Yoga Fitness Routine Beliefs Health And Wellness Creativity Enhancement Experimental Design Perform Analysis Interpret Placebo Responses Participant Beliefs Two-group Design Placebo Group Stretching Group

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