The term John Henry effect was coined to explain the unexpected outcome of an experiment caused by the control group's knowledge of its role within the experiment. The control group's perceived role as a baseline or a comparison group to the experimental condition, specifically one testing an innovative technology, can cause the control group to behave in an unnatural way to outperform the new technology. The group's knowledge of its position within the experiment as a baseline comparison causes the group to perform differently and, often more specifically, better than usual, eliminating the effect of the experimental manipulation. Deriving its name from the folktale the “Ballad of John Henry,” the John Henry effect is similar to the Hawthorne effect in which participant behavior changes as ...
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