Author's School

Graduate School of Arts & Sciences

Author's Department/Program



English (en)

Date of Award

January 2009

Degree Type


Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Leonard Green


Several experimental procedures: e.g., adjusting amount, adjusting delay) have been used to study the effect that changes in amount of and delay to a reward have on the reward's subjective value. The present series of three experiments sought to test the implicit assumption that the underlying decision-making process: discounting) is identical regardless of the procedure used, and that all would converge on similar indifference points. For each of the experiments, participants were initially tested on one of the adjusting tasks: Adjusting Immediate Amount, Adjusting Delayed Amount, or Adjusting Delay) and returned a week later to complete each of the remaining adjusting tasks. The indifference points obtained from the initial adjusting task were used as the test parameters in the other two tasks. That is, when participants completed the other two adjusting tasks, the amounts and delays experienced were identical to those from the initial adjusting task. Since, in the other adjusting tasks, the participants experience the identical amounts and delays as the initial adjusting task, specific predictions, at the level of the individual, were possible. Participants in all three experiments also completed a fully randomized version of the initial choice task. The results confirmed that, regardless of the choice task used, subjective value decreased as the delay to that outcome increased. In addition, it was found that under the adjusting-delay and the adjusting-delayed-amount tasks, but not under the adjusting-immediate-amount task, subjective value was determined not just by the amount of the outcome or the delay to its receipt, but to some degree by the manner in which the choices are presented: i.e., the context). Therefore, when investigating intertemporal choice, the adjusting-immediate-amount procedure appears to provide the most reliable and valid estimates of indifference between immediate and delayed outcomes.


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