title: Effects of reward bundling on male rats' preference for larger-later food rewards.
abstract: In both humans and nonhumans, prior research demonstrates increased preference for larger-later over smaller-sooner rewards when rewards are bundled together in a series (i.e., when an operant choice produces multiple discrete reward deliveries, as opposed to only a single delivery). These findings can be predicted using a traditional hyperbolic delay-discounting model. The present study was designed to examine the parametric effects of the size of the reward bundle on larger-later reward preference in male rats. During a reward-bundling phase, rats were exposed to bundle-sizes of either 1 (i.e., no bundling), 3, or 9 rewards. Rats in the Bundle-size 9 group showed significantly greater larger-later reward preference across a range of delays (0-17.5 s) than rats in any other group, but no other significant differences in choice were observed between groups. In addition, when choice for unbundled rewards was assessed following the reward-bundling phase, rats in the Bundle-size 9 group showed a significant increase in larger-later reward preference (compared to a pre-test). Obtained data from the reward-bundling phase are compared to model-predicted data, and potential mechanisms of the observed increase in self-control for unbundled rewards are discussed.
authors: Department of Psychology, Utah State University, 2810 Old Main Hill, Logan, UT 84322, USA. jeff.stein@aggiemail.usu.edu
authors: Jeffrey S
authors: JS
authors: Stein
authors: Rochelle R
authors: RR
authors: Smits
authors: Patrick S
authors: PS
authors: Johnson
authors: Kennan J
authors: KJ
authors: Liston
authors: Gregory J
authors: GJ
authors: Madden
mesh_terms: D000818:Animals; D002755:Choice Behavior; D003216:Conditioning, Operant; D007175:Impulsive Behavior; D007600:Judgment; D008297:Male; D051381:Rats / Q000523:psychology; D020318:Rats, Long-Evans; D012201:Reward; D013997:Time Factors