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Placebo

Last update: September 17, 2022
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By BrainMatters

A placebo is a "fake" drug or "fake" method.

In an experiment testing a drug researchers want to be able to "control" for certain effects of the treatment that have nothing to do with the drug. Imagine that a new drug for headaches is devised and researchers want to test whether it works. If the researchers just give 50 people that drug and ask them if they still have a headache after taking it, they may get the result that the headache did indeed decrease. But how does that happen? It is tempting to think that this difference was caused by the new drug. But it could also be that people got better on their own, that they got better because they had had some attention from a doctor, that they got better because they thought they were getting an effective drug, and so on. So a good scientific study has to figure out a way to rule out all these alternative explanations for the reduction in headaches. This is often done by using a second group of headache patients, who are unknowingly given a placebo drug (for example, a sugar pill). This group of people will - as has been shown in many situations - also be able to get a reduction in headaches. By testing both an experimental group and a placebo group of subjects in a study, where no one knows whether they are getting a real new drug or a "fake" drug, any differences in headache reduction between the experimental and placebo groups can be attributed to the newly developed drug. Therefore, the researchers fervently hope that the experimental group will have fewer headaches left than the placebo group!

As is the case with drugs or other remedies, a similar story can be applied to entire experimental procedures. For example, imagine an experiment involving TMS, a method of brain stimulation. For instance, researchers want to know if stimulation of frontal brain regions has an effect on attention. With an actual improvement in performance of an attention task, it is tempting to conclude that the frontal brain regions were indeed important for attention. But again, this would require a placebo condition, involving "fake" TMS. Because who knows, maybe the subjects were purely more attentive because they had just experienced such an exciting brain stimulation!

Author: Tom de Graaf (translated by Melanie Smekal)

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