One-year temporal stability of delay-discount rates.

The temporal stability of delay-discount rates for monetary rewards was assessed using a monetary choice questionnaire (Kirby & Marakovic, 1996). Of 100 undergraduate participants who completed the questionnaire at the initial session, 81 returned 5 weeks later and 46 returned 57 weeks later for subsequent sessions. The 5-week test-retest stability of discount rates was .77 (95% confidence interval = .67-.85), the 1-year stability was .71 (.50-.84), and the 57-week stability was .63 (.41-.77). Thus, at least when similar testing situations are reinstated, discount rates as individual differences have 1-year stabilities in the range that is typically obtained for personality traits. Discount rates index an attribute of the person that is relatively stable over time but that is moderated by aspects of the situation, such as reward type and deprivational state.