In 1924 America's National Research Council sent two engineers to supervise a series of industrial experiments at a large telephone-parts factory called the Hawthorne Plant near Chicago. It hoped they would learn how shop-floor lighting affected (选A) workers’ productivity. Instead, the studies ended up (选B) giving their name to the “Hawthorne effect”, the extremely influential idea that the very act (选C) of being experimented upon changes subjects’ behaviour.
The idea arose because of the perplexing (选B) behaviour of the women in the Hawthorne plant. According to  accounts (选C) of the experiments, their hourly output rose when lighting was increased, but also when it was dimmed. It did not matter (选B) what was done in experiment; so long as (选D) something was changed, productivity rose. An awareness (选A) that they were being experimented upon seemed to be enough (选C) to alter workers’ behaviour by (选D) itself.
After several decades, the same data were subjected (选C) to econometric analysis. The Hawthorne experiments had another surprise store contrary to (选A) the descriptions on record, no systematic evidence (选A) was found that levels of productivity were related to changes in lighting.
It turns out that peculiar way of conducting the experiments may have led to  misleading (选D) interpretations of what happened. For example (选B), lighting was always changed on a Sunday, when work started again on Monday, output  duly (选A) rose compared with the previous Saturday, and  continued (选D) to rise for the next couple of days. But（注：本题原文But后面没有逗号，海文版真题空格后面有逗号，如果选项里没有But，则此处可填however） a comparison with data for weeks when there was no experimentation showed that output always went up on Mondays. Workers tended to be diligent for the first few days of the working week in any case, before  hitting (选D) a plateau and then slackening off.