Figure 1.

Experimental design. Participants were shown two bowls containing 24 blue- and red-colored chips. In each trial, participants were presented with a reference bowl containing 12 blue and 12 red chips on the left side (same throughout the trial). In the risky trials (A), the composition of the variable bowl was visible. In the ambiguous trials (B), part of the variable bowl was hidden by a black occluder. The occluder was always placed over the center of the image. Participants could claim the winning payoff shown beside the color of the drawn chip.