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ERIC Number: EJ997542
Record Type: Journal
Publication Date: 2004-Jan
Pages: 12
Abstractor: As Provided
ISSN: ISSN-0022-5002
Discounting of Delayed Food Rewards in Pigeons and Rats: Is There a Magnitude Effect
Green, Leonard; Myerson, Joel; Holt, Daniel D.; Slavin, John R.; Estle, Sara J.
Journal of the Experimental Analysis of Behavior, v81 n1 p39-50 Jan 2004
Temporal discounting refers to the decrease in the present, subjective value of a reward as the time to its receipt increases. Results from humans have shown that a hyperbola-like function describes the form of the discounting function when choices involve hypothetical monetary rewards. In addition, magnitude effects have been reported in which smaller reward amounts are discounted more steeply than larger amounts. The present research examines the cross-species generality of these findings using real rewards, namely food pellets, with both pigeons and rats. As with humans, an adjusting amount procedure was used to estimate the amount of immediate reward judged equal in value to a delayed reward. Different amounts of delayed food rewards (ranging from 5 to 32 pellets in pigeons and from 5 to 20 pellets in rats) were studied at delays varying from 1 s to 32 s. A simple hyperbola, similar to the hyperbola-like mathematical function that describes the discounting of hypothetical monetary rewards in humans, described the discounting of food rewards in both pigeons and rats. These results extend the generality of the mathematical model of discounting. Rates of discounting delayed food rewards were higher for pigeons than for rats. Unlike humans, however, neither pigeons nor rats showed a reliable magnitude effect: Rate of discounting did not vary systematically as a function of the amount of the delayed reward. (Contains 1 table and 6 figures.)
Society for the Experimental Analysis of Behavior. Available from: Indiana University Department of Psychology. Bloomington, IN 47405. Tel: 812-334-0395; Fax: 812-855-4691; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A