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 stop-floor lighting affected  workers' productivity.

Instead, the studies ended  giving their name to the "Hawthorne effect", the extremely influential idea that the very act  to being experimented upon changed subjects' behavior.

请问上句中upon做什么成分 是什么意思呢？

百度到的upon用法，但还是不能理解

1. 等同於”on”

2. 等同於 “as soon as”

3. 強調「龐大的數量」

4. 表示「即將發生」