Temporal Discounting of Various Items to Examine Characteristics that Affect Rate of Discounting Kathryn R. Haugle, Rochelle R. Smits, & Daniel D. Holt Psychology Department, University of Wisconsin-Eau Claire Past research demonstrates that consumable rewards are discounted similarly to each other, yet differently than money, a generalized conditioned reinforcer (Estle, Green, Myerson, & Holt, 2007). Charlton and Fantino (2008) suggest the difference may be due to a metabolic function, where items that can be metabolized are discounted at a higher rate than items that cannot be metabolized. Charlton and Fantino (2008) also discovered that items that are exchangeable are discounted at a lower rate than items that are not exchangeable. The current study sought to examine more closely the affect of the level of exchangeability on the rate of discounting. The current study examined temporal discounting of several outcomes, all varying in the level of exchangeability. Results portray that all generalized outcome types (Visa Gift Card, Pizza Certificate, Clothing Gift Card, and Grocery Gift Card) were discounted at a lower rate than the less generalized outcome types (Cash, Pizza Slices, Jeans, and Candy). Also, the outcomes with the highest level of fungibility (Visa Gift Card and Cash) were discounted at a slightly lower rate than the outcomes with a medium level of fungibility (Clothing Gift Card and Grocery Gift Card), which were discounted at a slightly lower rate than the outcome with a low level of fungibility (Pizza Certificates), which were discounted at a slightly lower rate than the outcomes with no fungibility (Pizza Slices, Jeans, and Candy Bars). These results demonstrate that the rate of discounting may also be affected by level of fungibility in addition to a metabolic function. Future research should examine the relationship between metabolic function and level of fungibility in regards to the effect of rate of discounting. Future research should also examine temporal discounting of various outcome types that vary in the level of fungibility to assess the strength of the findings of the current study. Past research demonstrates that consumable rewards are discounted similarly to each other, yet differently than money, a generalized conditioned reinforcer (Estle, Green, Myerson, & Holt, 2007). Charlton and Fantino (2008) suggest the difference may be due to a metabolic function, where items that can be metabolized are discounted at a higher rate than items that cannot be metabolized. Charlton and Fantino (2008) also discovered that items that are exchangeable are discounted at a lower rate than items that are not exchangeable. The current study sought to examine more closely the affect of the level of exchangeability on the rate of discounting. The current study examined temporal discounting of several outcomes, all varying in the level of exchangeability. Results portray that all generalized outcome types (Visa Gift Card, Pizza Certificate, Clothing Gift Card, and Grocery Gift Card) were discounted at a lower rate than the less generalized outcome types (Cash, Pizza Slices, Jeans, and Candy). Also, the outcomes with the highest level of fungibility (Visa Gift Card and Cash) were discounted at a slightly lower rate than the outcomes with a medium level of fungibility (Clothing Gift Card and Grocery Gift Card), which were discounted at a slightly lower rate than the outcome with a low level of fungibility (Pizza Certificates), which were discounted at a slightly lower rate than the outcomes with no fungibility (Pizza Slices, Jeans, and Candy Bars). These results demonstrate that the rate of discounting may also be affected by level of fungibility in addition to a metabolic function. Future research should examine the relationship between metabolic function and level of fungibility in regards to the effect of rate of discounting. Future research should also examine temporal discounting of various outcome types that vary in the level of fungibility to assess the strength of the findings of the current study. We would like to thank UWEC’s Office of Research and Sponsored Programs for supporting this research. Introduction Method Individuals must make a vast amount of decisions every single day (e.g., what to wear, what to eat, what to do). Decisions are predictable when the alternatives differ in a single dimension (i.e., work for a job that has a large salary vs. a small salary, all else being equal). However, choices often involve outcomes that differ in multiple dimensions such as amount and delay (e.g., work a low-paying job right out of high school or receive a higher education for a higher-paying job in a few years). Previous research has found that instituting a delay to receiving a reward systematically decreases the subjective value (SV) of the reward. This effect has been termed temporal discounting (for a review see Green & Myerson, 2004). Researchers have examined the rate of temporal discounting of various outcomes, including consumable and non-consumable outcomes (Estle, Green, Myerson, & Holt, 2007; Odum & Rainaud, 2003). Results demonstrated a difference between the consumable outcomes (e.g. candy, soda, and alcohol) and money, a non-consumable, generalized conditioned reinforcer. Specifically, as the delay to receiving the outcomes increased, the SV of the consumable outcomes decreased significantly faster than the SV of the monetary outcome. Charlton and Fantino (2008) discovered that the SV of items that can be metabolized (food) decreased at a higher rate than the SV of items that cannot be metabolized (e.g., entertainment items). They also found that the SV of items that are exchangeable (i.e., money) are devalued at a lower rate than the SV of items that are not exchangeable (i.e., entertainment items). Due to these findings Charlton and Fantino (2008) suggest the outcome difference may be due to a metabolic function. Currently, no research has examined temporal discounting of items with varying levels of exchange. While money can be exchanged for a wide variety of goods, gift cards/certificates can be exchanged for a limited range of goods. The current study examined the discounting of various items in order to further examine how the range of goods affect the rate of discounting. Results Figure 1 shows the participants’ median area under the curve for all outcome types at both amounts. The dashed lines separate the conditions the participants completed in a between subject’s design. A 2x8 ANOVA was conducted to determine significance between outcome types as well as between amounts. There is a significant difference between the outcome types in each condition with F(1, 174) = 3.080, p =.004, where the more generalized outcome type in was discounted at a lower rate than the less generalized outcome type. There is also a significant difference between amounts with F(1,174) = 37.78, p =.001, where the larger amount of outcome type was discounted at a lower rate than the smaller amount of outcome type. There was no significant interaction between outcome types or amounts with F(7,174) = 1.696, p = participants completed an online decision-making task that was accessible from any computer with internet access. Each participant was randomly assigned to one condition (money, food, pizza, or clothing). The participants in the money condition made decisions regarding cash and money on a Visa gift card at six delays (1 week, 1 month, 6 months, 1 year, and 5 years) for two amounts ($20 and $300). The other three conditions were the exact same regarding delays and amount and only differed with regard to the outcome that participants made decisions regarding. The participants in the food condition made decisions regarding candy bars and money on a grocery store gift card at. The participants in the pizza condition made decisions regarding pizza slices and pizza certificates. The participants in the clothing condition made decisions regarding jeans and money on a clothing store gift card. Participants were informed that all outcomes were hypothetical, but to make their decisions as if they were real. At each amount, delay at outcome combinations participants made four decisions, after which a subjective value was determined that served as the immediate subjective value of the delayed outcome. The first decision was between the larger amount ($20 or $300) after the given delay, and half that amount immediately. Discussion More Value Less Value