Keynes (1921) and Ellsberg (1961) have articulated an aversion toward betting on an urn containing balls of two colors of unknown proportion to one with a 50-50 composition. Keynes views this as reflecting different preferences for bets arising from different sources of uncertainty. Ellsberg...

Andreoni and Sprenger (in press) report evidence that distinct utility functions govern choices under certainty and risk. I investigate the robustness of their result to the experimental design. I find that the effect disappears completely when a multiple price list is used instead of a convex...