The "Hawthorne Effect", one of the best-known experiments in sociology was con¬ducted before World War II at the Hawthorne plant of Western Electric. The management was eager to improve productivity and wanted to know what kind of incentives would encourage the workers to increase output. The researcher who investigated the problem, Elton Mayo, separated a group of women from the other workers and systematically var¬ied lighting, coffee breaks, lunch hours, methods of payment, and so on. At first, Mayo and his associates were delighted: each new change increased levels of productivity. But when the researchers found that productivity rose no matter which variables were involved, they became suspicious. When the workers were finally returned to their original conditions, their productivity rose yet again! Something was seriously wrong with the re¬searchers' theoretical assumptions. Whatever had caused the changes in the dependent variable – productivity – it was not the independent variables the experimenters had introduced, and from this point of view the experiment was a failure. But the reasons for the experiment's failure have taught sociologists a great deal. Production rose, it seems, because the women enjoyed all the attention they were getting: they became a tight-knit, cooperative group, they knew what effects the sociologists were trying to produce, and they did their best to please. This phenomenon – the contamination of the experiment by the subjects' assumptions about what the sociologist is trying to prove – is still known as the Hawthorne effect.