On both sides of the watershed representing the transition form closed to open system models, a second trend can be identified: a shift from rational to natural system models of analysis. It appears that this shift has occurred twice! It occurred for the closed system models in the late 1930s and early 1940s, as already described in Chapters 2 and 3-the rational system formulations exemplified by Weber's bureaucratic theory, Taylor's scientific management, and Simon's decision theory were challenged by the cooperative system views of Barnard, the human relations work of mayo, and the conflict models of gouldner and others.