Effects of reward bundling on male rats' preference for larger-later food rewards.
Delivering several small reinforcers in a rapid burst can teach learners to choose larger, delayed rewards.
01Research in Context
What this study did
Scientists gave male rats a choice. Take two pellets now or wait for six pellets later.
They tried a twist. Instead of one pellet at a time, they dropped nine tiny pellets in a row. The rats heard a short burst of clicks as each pellet arrived.
The team kept the bundle for several sessions, then took it away to see if the rats still waited.
What they found
When the large reward came as a nine-pellet bundle, most rats switched and waited for it.
Even after the bundle stopped, many rats kept picking the larger-later option. The brief burst of pellets had taught them to wait.
How this fits with other research
Yuwiler et al. (1992) showed that bigger single pellets make rats pause longer after eating. S et al. now show that several small pellets delivered fast can have the opposite effect: they increase waiting, not pausing.
Corfield-Sumner et al. (1977) and Ramer et al. (1977) found that spaced food deliveries trigger extra drinking. S et al. bundle the food instead of spacing it, and the rats work harder rather than drink more.
Together the papers say timing matters. Space food and you get side effects like polydipsia. Bundle food and you get self-control.
Why it matters
You can copy the bundle idea with human learners. Give three tiny reinforcers in a row, not all at once. A quick "good job, here's one... here's two... here's three" may help clients wait for bigger pay-offs like five-minute computer time. Try it during delay-tolerance drills next week.
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Join Free →During the next delay task, give three tiny pieces of praise or edibles in quick succession when the client picks the larger-later option.
02At a glance
03Original 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.
Journal of the experimental analysis of behavior, 2013 · doi:10.1002/jeab.11