TEMPORAL DISCOUNTING IN AN UNCERTAIN WORLD: THE ABSENCE OF PROBABILITY AND MAGNITUDE EFFECTS IN AN EXPERIENCE-BASED TASK

Author

James J. Cole, Southern Illinois University Carbondale

Date of Award

12-2011

Degree Name

Master of Arts

Department

Psychology

First Advisor

Young, Michael E.

Second Advisor

Jacobs. Eric A.

Third Advisor

Gilbert, David G.

Abstract

Previous research has suggested that the presence of global uncertainty in choice between delayed outcomes can reduce an individual’s sensitivity to delay. However, this “common ratio effect” has only been shown using hypothetical rewards, and the question of whether the same effect would be observed in an experience-based paradigm remains unanswered. Furthermore, human temporal discounting studies have found that larger rewards are discounted less steeply than smaller rewards, but no such effect is observed in nonhumans, and no effort has been made to reconcile these two results. To these ends, a first-person shooter video game was adapted to present participants with choices between outcomes that were both delayed and uncertain. Delayed outcomes took the form of shots from a weapon that “charged” to increase its power in the time between firings. Experiment 1 incorporated uncertainty by allowing for weapon misfires. Experiment 2 replicated Experiment 1 and also examined magnitude effects by manipulating overall reinforcement density. Participants were not given exact figures for delay or probability but instead had to learn them from experience. Participants showed sensitivity to the delay manipulation, discounting less when impatience was more disadvantageous, but neither the common ratio effect nor a magnitude effect was observed. Results are discussed in the context of experience-based decision making.