Figure 1.

Monetary decision-making tasks to assess risk and loss aversion in valuation. (A) Risk aversion task. In the gain condition, participants chose between a certain monetary gain ($20) and a probabilistic gain of larger magnitude. In the loss condition, they chose between a certain monetary loss (-$20) and a probabilistic loss of larger magnitude (or no loss). The amount of the probabilistic gain (or loss) was adjusted dynamically depending on each participant’s choices in two consecutive trials with the same condition and probability, until the participant’s subjective value of the probabilistic gain (or loss) was equal to the certain gain (or loss) of $20. For example, when the participant chose a probabilistic gain (gamble choice) over a certain gain of $20 for the given probability twice in a row, the magnitude of the probabilistic gain was reduced in a stepwise manner. The discount rate of probabilistic gain (or loss) with respect to the odds against winning (or losing) was then calculated, and its logarithm value was obtained as a normalized measure of risk aversion for each individual (see Methods). (B) Loss aversion task. In every trial, participants chose between a 50-50 gamble or status quo ($0). The amount of gain in the 50-50 gamble was systematically adjusted in a similar manner as the risk aversion task in (A), so that the participant’s subjective value of the 50-50 gamble approached $0, the status quo. At this indifference point, the participant’s subjective value of potential gain in the 50-50 gamble was exactly negated by the potential loss in the same gamble; thus, loss aversion λ was calculated as the ratio of the amount of gain to the amount of loss. In lay terms, this task determines for each participant the amount of likely gain that is required to overcome the potential loss, if they are to elect to enter into a gamble.