Decision, Risk, Social Interactions.

Summary This thesis is composed of three chapters constituting distinct contributions but related to the same focus, the theory of decision in risk. The first chapter deals with additively separable preferences with respect to probabilities. A simple axiomatization of variational preferences represented by a functional decomposing into a utility expectation term and an entropy term is deduced. The second chapter consists of an axiomatic foundation of interdependent preferences in the presence of social interactions, based on the model initially developed by Blume, Brock and Durlauf. The third chapter raises the question of the contribution of the probabilistic model of quantum physics to decision theory and its application to take into account the subjective perception of events by individuals.