Exploring the Reliability and Validity of the Experiential Discounting Task

Delay discounting is the devaluation of rewards that are delayed in time. This phenomenon was first studied with animals in controlled laboratory environments and later translated to human procedures. Though the decrease in value of outcomes as the delay to receipt increases is the same across species (money for humans, food for animals), a number of methodological concerns have been raised about the procedures used to study delay discounting in humans. The Experiential Discounting Task (EDT) was recently developed in order to study delay discounting in humans in a way that is more similar to that used with animals. That is, humans make repeated decisions concerning outcomes they experience within session (delays and rewards). The EDT has proven useful for a variety of reasons including its ability to detect changes in how delayed rewards are discounted as a function of acute alcohol where traditional measures have not. However, this measure has yet to undergo rigorous tests of internal validity and reliability that previous measures of delay discounting have. In two experiments we tested the reliability and internal validity of the EDT. First we assessed the test-retest reliability across seven days. Next we tested whether the way in which choices are presented in the EDT affects choice. In addition, all participants completed a traditional delay discounting task, boredom proneness scale and probability discounting task. Experiment 1 resulted in good test-retest reliability for all tasks, including the EDT and the traditional measure of delay discounting. In Experiment 2 we found that individual performance did not change as a function of how choices were presented. Across both experiments we found no evidence for a correlation between discounting in the EDT and the traditional measure. Though reliable across time we contend, based on the relation to a traditional delay discounting task and the reviewed literature that there is little evidence that the EDT is a valid measure of delay discounting and call for more research to determine what process underlies decision-making in the EDT.