ABSTRACT

In experimental research, a confound is an extra variable that creates confusion regarding the explanation for a given difference. One important source of confounding is the Hawthorne Effect, which can be thought of as the attention effect. This effect was discovered in a series of industrial psychology studies at the Hawthorne Plant of Western Electric. A related confound is the John Henry Effect, named for the prodigiously hardworking 19th century folk hero. Researchers should try to conceal the control group's knowledge of its status whenever possible. When administering a placebo, researchers say they are using a blind procedure when they do not disclose to the participants whether they are receiving an active or inactive substance. Researchers who study the effectiveness of medications usually are concerned with the confounding placebo effect. Demand characteristics can also be a source of confounding. A demand characteristic is a cue that lets participants know the expected outcome of an experiment.