Between 1924 and 1933, a series of the Hawthorne studies was conducted by researchers, including Elton Mayo, of the Hawthorne Works which belonged to the Western Electric Company. Scientists attempted to determine the relation between work environment and productivity over the series of the Hawthorne studies. The first series of studies, called The Hawthorne Illumination Tests (HIT), was performed between 1924 and 1927. The purpose was just to find the optimal lighting for productivity (Sheldrake 1998, p.105). These experiments had two groups, control group (the group with lighting changed) and experimental group. Surprisingly, both of their performance enhanced at last, whether illumination declined or not. Due to Sheldrake’s viewpoint (1998, p.108), the results showed that there was no clear relationship between the intensity of lighting and the rate of output. Thus, researchers realised that there could be something else besides lighting to affect productivity. They doubt that the supervision of the researchers may have some effects on it. (<http://en.wikipedia.org/wiki/Hawthorne_effect>, March 2006).
After the first experiment, researchers wanted to identify what other elements could influence productivity, so they began to perform the second set of studies