In 1924 the National Research Council set out to answer a narrow question at Western Electric’s Hawthorne Works outside Chicago: does better lighting make workers more productive? Its committee on industrial lighting counted Thomas Edison as honorary chairman, and the electrical industry had a considerable investment in the answer being yes.
The test ran until 1927. The workers were women who mostly assembled telephone relays and wound coils of wire. Engineers raised and lowered the light, made each change on a Monday, and told the workers about it.
The results would not line up. In one test, a group working under changing light and a control group under steady light both improved. Then two “capable and willing operators” had their light cut to 0.06 of a foot-candle, “an amount of light approximately equal to that on an ordinary moonlight night.” They kept up their efficiency.
In another round, an electrician came in and changed the bulbs, swapping them for bulbs of the same power. The women commented on whether they preferred the old light or the new one.
No final report was ever published. A historian later suggested why: its recommendation, 7 to 10 foot-candles, would have disappointed an industry hoping for scientific backing for brighter lights.
The story grew without the numbers. A 1982 research methods textbook told students that every change raised output, even a return to poor light: “Seemingly perversely, productivity continued to rise.” That same year, Tom Peters and Robert Waterman passed on a friend’s remark that many of the best companies seemed to reduce management to “an endless stream of Hawthorne effects.”
The original data were thought destroyed. In the 2000s, the economists Steven Levitt and John List traced them to a microfiche room in a small library in Milwaukee, which held the records for one department, and to a forgotten archive in Boston, which held the other two.
The records were charts, so they read the numbers off the graphs and ran them. In the first year, output in all three rooms climbed to a peak about 10 percent above where it started, which looks like the legend. Later, a room that had left the experiment rose too, and output in every room fell in summer, a pattern the authors read as seasonal.
Then they looked at Mondays. Output rose sharply on the Mondays the lights were changed. It rose in the same way on Mondays when nothing had changed at all. The biggest swings followed the days of the week, not the light. The descriptions of remarkable patterns in these data, they wrote in 2009, “prove to be entirely fictional.” In the same breath they noted “hints of more subtle manifestations of a Hawthorne effect.” What fell was the famous pattern, not the idea that being watched can change behavior.