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| Discounting |
| Monday, May 31, 2004 |
| 10:30 AM–11:20 AM |
| Commonwealth |
| Area: EAB |
| Chair: Mark E. Berg (University of Canterbury) |
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| Risk Sensitivity and Dynamic Intertemporal Choice in an Electronic Foraging Task |
| Domain: Applied Research |
| CARTER L. SMITH (Temple University), Donald A. Hantula (Temple University) |
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| Abstract: Scenarios used in human delay-discounting research typically have little in common with the decisions people make in real financial environments where molecular intertemporal choices are nearly always part of a sequence of decisions tied to some larger, extended set of contingencies. The current study attempted to model such scenarios, and assessed the possibility that molar environmental constraints might influence sequential intertemporal choice. Eighty-two participants played an electronic video game involving a spaceship that searches for items on planets. During the game participants made a series of decisions regarding fuel for the spaceship. Smaller amounts of fuel were available immediately, while larger amounts accompanied varying delay periods. Successful completion of the game resulted in a cash reward. Based on relationships between risk sensitivity and daily energy budgets in foraging theory, it was hypothesized that successive intertemporal choices would reflect modulating sensitivity to delay under manipulations of several environmental constraints: remaining game time and rate of fuel depletion. As hypothesized, emitted decisions reflected progressively steeper discounting. The results suggest that, in the present context, sensitivity to delay is dynamic. The need for ongoing consideration of broader contextual controls on delay discounting is discussed. |
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| Effects of Initial-Link Duration on Acquisition of Preference in Concurrent Chains |
| Domain: Applied Research |
| MARK E. BERG (University of Canterbury), Randolph C. Grace (University of Canterbury) |
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| Abstract: Asymptotic response allocation during the initial links of concurrent chains becomes less extreme as the absolute duration of the initial links increases with the terminal links held constant (“initial-link effect”; Fantino, 1969). The present study asked whether initial-link duration also affected acquisition of preference, i.e., how quickly response allocation reached asymptote. Six pigeons were trained on a concurrent-chains procedure in which the terminal links were FI 8 s FI 16 s or FI 16 s FI 8 s and were changed every 20 sessions. Across conditions, all possible combination of transitions between relatively short (VI 8 s) and long (VI 24 s) initial-link schedules were studied. Overall, rate of acquisition (measured as the proportion of eventual change in response allocation) was fastest when the initial-link duration preceding the reversal was short and when the initial-link duration following the reversal was long; slowest when the preceding initial-link duration was long and the following duration was short; and intermediate with short-short and long-long transitions. These results show that a successful model for acquisition of preference in concurrent chains must incorporate initial- as well as terminal-link variables (cf. Grace, 2002). |
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