It had become clear that the itemized changes experimentally imposed, although they could perhaps be used to account for minor differences between on… - Elton Mayo

The history of the twelve-week return to the so-called original conditions of work is soon told. The daily and weekly output rose to a point higher than at any other time and in the whole period "there was no downward trend." At the end of twelve weeks, in period thirteen, the group returned, as had been arranged, to the conditions of period seven with the sole difference that whereas the Company continued to supply coffee or other beverage for the mid-morning lunch, the girls now provided their own food. This arrangement lasted for thirty-one weeks—much longer than any previous change. Whereas in period twelve the group's output had exceeded that of all the other performances, in period thirteen, with rest-pauses and refreshment restored, their output rose once again to even greater heights

The human aspect of industry has changed very considerably in the last fifty years. The nature and range of these changes are still partly unknown to us, but the question of their significance is no longer in dispute. Whereas the human problems of industry were regarded until recently as lying within the strict province of the specialist, it is now beginning to be realized that a clear statement of such problems in particular situations is necessary to the effective thinking of every business administrator and every economic expert.

Acting in collaboration with the National Research Council, the Western Electric Company had for three years been engaged upon an attempt to assess the effect of illumination upon the worker and his work.