Hawthorn effect debunked

23453_lI grew up near Western Electric’s Hawthorn Works on Chicago’s West Side. Although it closed in 1984, the facility’s name lived on in the Hawthorn Effect, a kind of Heisenberg principle for the social sciences which claimed that subjects change their behavior in response to the mere fact of being observed.

The idea came from a series of industrial experiments carried out at the plant in the 1920s. Researchers found that production output increased after they raised lighting levels on an assembly line. They took another assembly line and lowered the lighting levels, and found that output increased on that line as well. The conclusion was that the change in lighting levels told the workers they were being observed, and they changed their behavior accordingly.

According to this article in the Economist, Steve Levitt (of Freakonomics fame) and colleague John List dug up the original data from these experiments and found some serious flaws in the methodology. For example, it turns out that lighting levels were always changed on Sundays. The researchers then compared Monday’s output with that of the previous Friday. But there was a natural tendency for workers to be more productive at the beginning of the week than at the end: workers were always more productive on Mondays than on Fridays. When Levitt and List reanalyzed the data to correct this effect, the Hawthorn Effect disappeared.

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2 Responses

  1. […] Alternative Blog has a post this morning entitled Hawthorne effect debunked. The original Hawthorne effect was apparently due to a flaw in the study design; correcting for […]

  2. While the results of the study may offer evidence that the original analysis was flawed its longevity is testament to the fact that, as many researchers will have observed, when a ‘control’ group is able to influence outcomes through behaviour alone, their value as a control group is greatly diminished.

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