Hawthorne Effect Found to be Bogus

August 13th, 2009 | Sources: Economist

In 1924, the National Research Council dispatched 2 engineers to study the effects of shop-floor lighting on productivity at the Hawthorne Plant, a telephone-parts factory near Chicago.

HawthornePlantworkerTheir observations led to an unexpected, but soon-to-be widely accepted principle of management science. The “Hawthorne Effect” posits that being observed, whether by a scientist or a supervisor, changes peoples’ behavior.

The phenomenon was derived from the engineers’ accounts of their experiments, in which they observed that the output of workers on an assembly line increased when lighting was raised in the factory, but also when it was lowered.

The worker’s behavior improved, it appeared, when they realized they were being watched.

Many had questioned the validity of those conclusions, and the original data was thought to have been lost.

Recently however, University of Chicago economists Steven Levitt and John List discovered the data and decided to reanalyze them using new econometric techniques.

The pair concluded that worker productivity at the Hawthorne plant did not change in response to lighting alterations at the plant, and that the engineers’ incorrect interpretation resulted from an epiphenomenon they had not accounted for.

The engineers, it turns out, always adjusted plant lighting on Sundays, when the plant was closed. Monday’s worker output was indeed greater than Saturday’s, but that was true even for weeks in which no adjustment was made to the lighting on Sundays.

Levitt and List concluded that workers just worked harder on Mondays.

Similarly, the engineers had noted that plant output fell after their experiment ended, which supported their conclusion. But they ceased experimentation during the summer. The economists found that similar summer drop-offs occurred in the years before and after the engineers ran their trials.

It does get hot in Chicago in the summer, after all.


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