Impulsive choice, alcohol consumption, and pre-exposure to delayed rewards: II. Potential mechanisms.
Practicing long waits cuts impulsive picks, but it will not shrink alcohol or sugar intake.
01Research in Context
What this study did
Researchers gave rats a taste of waiting. The rats first lived with a 17.5-second delay before every food pellet. Later, the rats chose between a small pellet right away or a big pellet after another long wait.
The team also let the rats drink alcohol and sugar water to see if the delay training would cut drinking.
What they found
The delay-trained rats picked the big-later reward more often. Their impulsive choices dropped. But the rats drank the same amount of alcohol and sugar water as before. The earlier belief that delay exposure cuts drinking did not repeat here.
How this fits with other research
Schmitt (1984) used similar concurrent-chain tests and showed that longer terminal links also shift choice. The new study adds that just living through a long delay can do the same thing.
Gowen et al. (2013) saw pigeons flip from impulsive to self-controlled as delays grew within a session. The rat study shows the flip can also be trained ahead of time with pre-exposure.
Green et al. (2004) found no magnitude effect in discounting. The current work agrees: reward size did not change how the rats viewed the delays.
Why it matters
If you want clients to wait for bigger pay-offs, let them practice waiting first. A short daily routine with built-in delays can build patience. Do not count on this trick to cut problem drinking or over-eating; the rat data say the effect stops at choice, not consumption.
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02At a glance
03Original abstract
In a prior study (Stein et al., 2013), we reported that rats pre-exposed to delayed rewards made fewer impulsive choices, but consumed more alcohol (12% wt/vol), than rats pre-exposed to immediate rewards. To understand the mechanisms that produced these findings, we again pre-exposed rats to either delayed (17.5 s; n=32) or immediate (n=30) rewards. In posttests, delay-exposed rats made significantly fewer impulsive choices at 15- and 30-s delays to a larger, later food reward than the immediacy-exposed comparison group. Behavior in an open-field test provided little evidence of differential stress exposure between groups. Further, consumption of either 12% alcohol or isocaloric sucrose in subsequent tests did not differ between groups. Because Stein et al. introduced alcohol concentration gradually (3-12%), we speculate that their group differences in 12% alcohol consumption were not determined by alcohol's pharmacological effects, but by another variable (e.g., taste) that was preserved as an artifact from lower concentrations. We conclude that pre-exposure to delayed rewards generalizes beyond the pre-exposure delay; however, this same experimental variable does not robustly influence alcohol consumption.
Journal of the experimental analysis of behavior, 2015 · doi:10.1002/jeab.116