“The Pervasive Problem With Placebos in Psychology: Why Active Control Groups Are Not Sufficient to Rule Out Placebo Effects”


Proper methodological design is paramount for any scientific study, especially those making causal claims. In a recent article, Boot et al. demonstrate that many psychology studies fail to control for differences in expectation between participants in the control and experimental groups. For many studies, the effects observed in the experimental group may in fact be due to the placebo effect of expectation, rather than the intervention itself, calling into question any causal claims. Through a case study and a simple test of expectations, Boot and colleagues show that expectations do infact differ between the control and experimental groups, and how the failure to control for such differences can lead to faulty or at least premature claims of causation. To help remedy this pervasive problem, the authors point to certain methodological designs that can control for expectations, and call on researchers, reviewers, and editors to set a higher methodological standard when making causal claims for a psychological intervention.

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