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Research Mentor and Department
Most research on delay and probability discounting has examined choices in “one shot” scenarios. Many everyday situations, however, involve repeated choices. The current study compared the effect of repeated gambles with “one-shot” gambles on rates of discounting. One hundred participants were randomly assigned to one of 4 conditions that differed in the amount of a probabilistic hypothetical reward ($50 and $2,000) and the delay between gambles (1 week and 2 months). In each condition, participants were offered a series of choices between receiving a smaller amount for certain and playing a game for the chance to receive the larger amount. The game involved repeated gambles to win the larger amount, with a constant probability of winning on each gamble. Within conditions, the probability of winning the larger amount varied from 80% to 5%. In addition, the number of tries the participants were permitted to win the gamble varied from 1 (a one-shot) to unlimited. No overall effect of amount of the probabilistic reward on discounting rate was observed. However, the larger probabilistic amount was discounted more steeply in the “one shot” gamble condition (consistent with the reverse-amount effect obtained with probability discounting), whereas the larger probabilistic amount was discounted less steeply in the unlimited gambles condition (consistent with the amount effect obtained in delay discounting). Furthermore, rate of discounting increased as the delay between repeated gambles increased from 1 week to 2 months and as the number of tries to win the reward decreased. The current results are the first to show that the hyperboloid function accurately describes patterns of discounting under situations involving repeated gambles. Moreover, the results provide support for the hypothesis that when given multiple opportunities to win a probabilistic reward, subjective value is a function of the expected delay rather than the probability of reward.