The central character of economy is the homo oeconomicus, which is a model that rep-resents the ideal of economic behavioral theory. The homo oeconomicus acts according to its maximum of utility and it also acts rationally in terms of its own target function. In a normative view the model is indisputable. However, in a descriptive view the model does not always succeed in explaining human decision behavior. The main goal of this master thesis is to show the systematic deviations of the model of the homo oeconomicus in terms of its decision behavior. The focus is thereby set on the anomalies which are caused by the limited cognitive competences of individuals. In the first part of the thesis paper the basic principles of decision-making theory like the Bernoulli-principle and the prospect theory are illustrated. This is followed by an excursus on the model of the homo oeconomicus. The second part of the thesis paper focuses on the term rationality, with the objective to illustrate the deviations of rational decision behav-ior, followed by an introduction into the different concepts of limited rationality. In the third part of the paper the anomalies of the decision behavior, as well as the cognitive processes that go with it, are illustrated. Finally, in the fourth part of the paper the eco-nomic relevance of these anomalies of decision-making are discussed, including the analysis of the significance of institutions in preventing these anomalies. Furthermore, the role of the controlling as an institution that secures rationality is discussed, and pos-sible measures for a prevention of these anomalies are introduced. As for internal deci-sion-making processes, the controllers and managers represent a team, in which the con-troller has taken over the function of the critical counterpart. In order to live up to the requirements of this function, it is advisable for controllers to have adequate psycholog-ical skills besides their in-depth expertise.