The New Palgrave Dictionary of Economics

2018 Edition
| Editors: Macmillan Publishers Ltd

Ambiguity and Ambiguity Aversion

  • Marciano Siniscalchi
Reference work entry


Experimental evidence strongly suggests that subjects facing a decision under uncertainty often find it difficult to assess the relative likelihood of certain events; decision theorists deem such events ‘ambiguous’. Furthermore, subjects generally dislike options (acts) whose final outcome depends upon the realization of such ambiguous events; that is, they are ‘ambiguity-averse’. This article surveys the main decision-theoretic models developed since the mid-1980s to accommodate ambiguity and ambiguity aversion, including Choquet-expected utility (Schmeidler. Econometrica 57: 571–87, 1989) and maxmin expected utility (Gilboa and Schmeidler. J Math Econ 18: 141–53, 1989). More recent developments in the theory of ambiguity are also briefly summarized.


Ambiguity Ambiguity aversion Bernoulli utility function Choice under uncertainty Choquet-expected utility Decision theory Decision weights Ellsberg paradox Incomplete preferences Maximum likelihood Maxmin expected utility Multiple priors Preference reversals Probability Savage, L Second-order probabilities Subjective expected utility Sure-thing principle von Neumann–Morgenstern utility function 

JEL Classifications

D1 D8 
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Copyright information

© Macmillan Publishers Ltd. 2018

Authors and Affiliations

  • Marciano Siniscalchi
    • 1
  1. 1.