Mayo contended that the effect was due to the workers reacting to the sympathy and interest of the observers. He did discuss the study as demonstrating an experimenter effect but as a management effect: how management can make workers perform differently because they feel differently. He suggested that much of the Hawthorne effect concerned the workers feeling free and in control as a group rather than as being supervised. The experimental manipulations were important in convincing the workers to feel this way, that conditions in the special five-person work group was really different from the conditions on the shop floor. The study was repeated with similar effects on mica-splitting workers.