In 1924 America’s National Research Council sent two engineers to supervise a series of experiments at a telephone-parts factory called the Hawthorne Plant near Chicago. It hoped they would learn how shop-floor lighting_____（1）workers’productivity. Instead, the studies ended_____（2）giving their name to the“Hawthorne effect”,the extremely influential idea that the very _____（3）of being experimented upon changed subjects’ behavior.

The idea arose because of the _____（4）behavior of the women in the plant.According to _____（5）of the experiments, their hourly output rose when lighting was increased, but also when it was dimmed. It did not _____（6）what was done in the experiment;_____（7）something was changed, productivity rose.A(n)_____ （8）that they were being experimented upon seemed to be_____（9）to alter workers’ behavior _____（10）itself.

After several decades, the same data were_____（11）to econometric analysis. The Hawthorne experiments had another surprise in store. _____（12）the descriptions on record, no systematic _____（13）was found that levels of productivity were related to changes in lighting.

It turns out that the peculiar way of conducting the experiments may have led to_____（14）interpretations of what happened._____（15）, lighting was always changed on a Sunday. When work started again on Monday, output _____（16）rose compared with the previous Saturday and _____（17）to rise for the next couple of days._____（18）, a comparison with data for weeks when there was no experimentation showed that output always went up on Mondays. Workers_____（19）to be diligent for the first few days of the week in any case, before _____（20）a plateau andthen slackening off. This suggests that the alleged “Hawthorne effect” is hardto pin down