Date of Award
Doctor of Philosophy (PhD)
The value of an outcome is affected both by the delay until its receipt (delay discounting) and by the likelihood of its receipt (probability discounting). The discounting framework has greatly aided in modeling and understanding decision-making, particularly in the areas of impulsivity, but these findings have overwhelmingly been based on research with young adults. In three experiments, the current study extended the discounting framework by examining choice by older adults. Experiments 1 and 2 found that both young and older adults discounted delayed outcomes and probabilistic outcomes and that their choices were well-described by the same hyperboloid model. Both young and older adults also showed magnitude effects with delayed rewards, reverse magnitude effects with probabilistic rewards, and no systematic effect of amount with delayed or probabilistic losses. In Experiment 3, in which choice was more complex and involved rewards that were both delayed and probabilistic, a multiplicative hyperboloid model in which delay and probability interacted to affect the subjective value of an outcome, described choice well for both young and older adults. Across the three experiments, some differences across young and older adults emerged. Older adults in Experiment 1, for example, showed a magnitude effect for delayed gains only up to $3,000, whereas young adults continued to show a magnitude effect for much larger amounts. Experiments 1 and 2 revealed differences in the degree of delay, but not probability discounting, after income was controlled, such that older adults discounted delayed rewards less steeply than young adults. Finally, in Experiment 3, older adults tended to show greater risk-aversion than young adults when outcomes were both delayed and probabilistic. In spite of the age differences observed, there was remarkable consistency in discounting across young and older adults. The results of the current study suggest that although there are quantitative age differences in decision making, choice appears qualitatively similar across age groups.
Chair and Committee
Todd S. Braver, Sandra Hale, Robyn A. LeBoeuf, Joel Myerson,
Vanderveldt, Ariana, "Decision Making in Older Adults: A Comparison of Delay and Probability Discounting Across" (2016). Arts & Sciences Electronic Theses and Dissertations. 805.