Zimper, Alexander2016-11-302016-11-302011-09Zimper , A 2011, 'Do Bayesians learn their way out of ambiguity?', Decision Analysis, vol. 8, no. 4, pp. 269-285.1545-8490 (print)1545-8504 (online)10.1287/deca.1110.0217http://hdl.handle.net/2263/58314In standard models of Bayesian learning agents reduce their uncertainty about an event s true probability because their consistent estimator concentrates almost surely around this probability s true value as the number of observations becomes large. This paper takes the empirically observed violations of Savage s (1954) sure thing principle seriously and asks whether Bayesian learners with ambiguity attitudes will reduce their ambiguity when sample information becomes large. To address this question, I develop closed-form models of Bayesian learning in which beliefs are described as Choquet estimators with respect to neo-additive capacities (Chateauneuf, Eichberger, and Grant 2007). Under the optimistic, the pessimistic, and the full Bayesian update rule, a Bayesian learner s ambiguity will increase rather than decrease to the e¤ect that these agents will express ambiguity attitudes regardless of whether they have access to large sample information or not. While consistent Bayesian learning occurs under the Sarin-Wakker update rule, this result comes with the descriptive drawback that it does not apply to agents who still express ambiguity attitudes after one round of updating.enINFORMS © 2011Non-additive probability measuresBayesian learningChoquet expected utility theoryPostprint Article