Question-based assessments of delay discounting: do respondents spontaneously incorporate uncertainty into their valuations for delayed rewards?

This research was designed to determine if, and to what extent, participants incorporate uncertainty into their valuations for delayed rewards when completing measures of delay discounting, even though uncertainty is not specified in the delay-discounting questions. Twenty-four adolescent participants completed a question-based measure of delay discounting and immediately following answered questions about perceived certainties of receiving the delayed rewards. Results showed that respondents rated the delayed rewards as increasingly uncertain with longer delays. Also, ratings of uncertainty were correlated with rate of delay discounting (r=0.55). These findings suggest participants automatically evaluate delayed rewards as uncertain when using this assessment procedure. The current finding may hold important implications for future addiction research in interpreting why addicted persons often discount more by delay than non-addicted controls, i.e., delay to reward or uncertainty about delayed rewards?