Fig. 1.

Task. (A) The sequence of events in free- and forced-choice trials. In the forced-choice trials, monkeys were required to choose color-matched targets. Positions of the risky and certain options were fixed during a payoff condition in a block. (B) Choice matrix: In each payoff condition the monkey would choose between a certain fixed amount of juice and a lottery that would deliver a reward with 50% probability (five different risky reward magnitudes per condition). For example, in payoff condition 1, the certain 60-μL reward was represented by a 1/10th-filled pie chart and the risky option by a pie chart ranging from empty to 4/10th full. Risky options with expected value equal to the certain option are shown in blue. (C) Example payoff condition sequence (randomly selected without replacement until all four payoffs were presented).