Range convexity and ambiguity averse preferences

We show that range convexity of beliefs, a 'technical' condition that appea rs naturally in axiomatizations of preferences in a Savage-like framework, imposes some unexpected restrictions when modelling ambiguity averse prefer ences. That is, when it is added to a mild condition, range convexity makes the preferences collapse to subjective expected utility as soon as they sa tisfy structural conditions that are typically used to characterize ambigui ty aversion.