We design and implement lab experiments, as close as possible to the Ellsberg two-color urn experiment, to evaluate the positive and normative appeal of behavior arising from models of ambiguity-averse preferences. We report three main empirical findings: First, these preference models do not...

We study the potential evolutionary appeal of rationality in a model in which different populations differ with respect to their experimentation over rules of behavior. We show that more risky experimentation in the sense of mean preserving spread dominates less risky experimentation....

Within a standard stochastic evolutionary framework, we study the evolution of morality, both at the level of behavior and at the level of codes of behavior. These moral codes involve sanctioning deviant agents. We provide conditions under which the presence of any small degree of inter-group...