Ecole Des Hautes Etudes Commerciales De Paris

From Ellsberg to Machina : Confronting decision models under ambiguitywith experimental evidenceHow do decision makers act and how should they act when confronted with uncertainty ?Economic behavior under uncertainty is often influenced by the informational structureof the decision context. Remarkably, the joint presence (juxtaposition or combination) oftwo sources of uncertainty namely risk (known probability) and ambiguity (unknownprobability of events) gives rise to behaviors that depart from standard models of de-cision making, subjective expected utility and its extension to non-additive probability,Choquet expected utility ; the essential behavioral component beyond paradoxes of un-certainty is (non neutral) attitude toward ambiguity. The studies reported in this thesisempirically investigate the heterogeneity of ambiguity attitudes in the light of the variabi-lity of the features of uncertainty. They deal with two main sorts of cases : the case wherea decision maker faces two separate sources of uncertainty (two-color Ellsberg paradox) ;the case where a decision maker faces mixed sources of uncertainty (Machina paradox).