Human decision-making behavior is the subject of investigation in numerous scientific disciplines. This book contains current research findings from the decision theory and practice working group of the Society for Operations Research. It provides new insights in the areas of multi-criteria decision theory and the formulation of decision models, as well as evaluations of laboratory experiments on decision-making behavior in both individual and collective contexts. In particular, questions regarding the concrete formulation of a decision situation and the handling of multiple objectives are discussed in depth. Furthermore, the concept of laboratory experiments is utilized to highlight deviations of actual decision-making behavior from theoretical solutions. Typical decision patterns are uncovered and linked to new explanatory approaches.