Probability discounting of gains and losses: implications for risk attitudes and impulsivity.

Sixty college students performed three discounting tasks: probability discounting of gains, probability discounting of losses, and delay discounting of gains. Each task used an adjusting-amount procedure, and participants' choices affected the amount and timing of their remuneration for participating. Both group and individual discounting functions from all three procedures were well fitted by hyperboloid discounting functions. A negative correlation between the probability discounting of gains and losses was observed, consistent with the idea that individuals' choices on probability discounting tasks reflect their general attitude towards risk, regardless of whether the outcomes are gains or losses. This finding further suggests that risk attitudes reflect the weighting an individual gives to the lowest-valued outcome (e.g., getting nothing when the probabilistic outcome is a gain or actually losing when the probabilistic outcome is a loss). According to this view, risk-aversion indicates a tendency to overweight the lowest-valued outcome, whereas risk-seeking indicates a tendency to underweight it. Neither probability discounting of gains nor probability discounting of losses were reliably correlated with discounting of delayed gains, a result that is inconsistent with the idea that probability discounting and delay discounting both reflect a general tendency towards impulsivity.