<P> Mayo contended that the effect was due to the workers reacting to the sympathy and interest of the observers . He does say that this experiment is about testing overall effect, not testing factors separately . He also discusses it not really as an experimenter effect but as a management effect: how management can make workers perform differently because they feel differently . A lot to do with feeling free, not feeling supervised but more in control as a group . The experimental manipulations were important in convincing the workers to feel this way: that conditions were really different . The experiment was repeated with similar effects on mica - splitting workers . </P> <P> Clark and Sugrue in a review of educational research say that uncontrolled novelty effects cause on average 30% of a standard deviation (SD) rise (i.e. 50%--63% score rise), which decays to small level after 8 weeks . In more detail: 50% of a SD for up to 4 weeks; 30% of SD for 5--8 weeks; and 20% of SD for> 8 weeks, (which is <1% of the variance). </P> <P> Harry Braverman points out that the Hawthorne tests were based on industrial psychology and were investigating whether workers' performance could be predicted by pre-hire testing . The Hawthorne study showed "that the performance of workers had little relation to ability and in fact often bore an inverse relation to test scores ...". Braverman argues that the studies really showed that the workplace was not "a system of bureaucratic formal organisation on the Weberian model, nor a system of informal group relations, as in the interpretation of Mayo and his followers but rather a system of power, of class antagonisms". This discovery was a blow to those hoping to apply the behavioral sciences to manipulate workers in the interest of management . </P> <P> The economists Steven Levitt and John A. List long pursued without success a search for the base data of the original illumination experiments, before finding it in a microfilm at the University of Wisconsin in Milwaukee in 2011 . Re-analysing it, they found that the variance in productivity could be fully accounted for by the fact that the lighting changes were made on Sundays and therefore followed by Mondays when workers' productivity was refreshed by a day off . This finding supported the analysis of an article by SRG Jones in 1992 examining the relay experiments . Despite the absence of evidence for the Hawthorne Effect in the original study, List has said that he remains confident that the effect is genuine . </P>

Who studied effect of fatigue on performance management