Testing delay of gratification in rats using a within‐session increasing‐delay task
Rats switch from waiting to grabbing as delays grow, but practice helps them wait longer.
01Research in Context
What this study did
Haynes et al. (2022) gave rats a simple choice. Press one lever and get two food pellets right away. Press the other and get six pellets, but the delay grows longer each time.
The delays started at one second and rose to 60 seconds within the same session. The team watched how often the rats switched from waiting to grabbing the small, fast reward.
What they found
Every rat flipped its choice. Early in the session they waited for the big pile of pellets. Once the delay hit about 20 seconds they quit waiting and took the small, quick reward.
The more days the rats played the game, the longer they stayed with the big reward. Experience trimmed their impulsive exits.
How this fits with other research
Gowen et al. (2013) saw the same flip in pigeons. Birds also switched from patient to impulsive as delays rose within a session. The new study shows the pattern holds across species.
Older rat work set the stage. Skrtic et al. (1982) and Ghaziuddin et al. (1996) mapped how rats balance amount and delay. Haynes et al. extend those maps by showing the flip happens in real time, not just across separate days.
Ahlborn et al. (2008) warn that within-session ascending delays can hide strain differences. Their data say between-condition tests give cleaner results. Haynes confirms the within-session method works for showing preference reversals, but J et al. remind us it may not catch every nuance.
Why it matters
You now have a lab model for teaching delay tolerance. Start with short waits, then stretch the delay within the same lesson. The rat data say learners will try to quit early; repeated practice makes them stick longer. Try this shape when building self-control with clients who grab the first reinforcer they see.
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02At a glance
03Original abstract
In delay discounting, preference reversals refer to shifts in preference from a larger-later reward to a smaller-sooner reward. Steep hyperbolic discounting predicts a preference reversal when a smaller-sooner and larger-later reward both become temporally proximal; prior research is consistent with this prediction. Hyperbolic discounting does not predict a preference reversal, however, after an individual chooses a larger-later reward over a smaller-immediate reward; prior research is inconsistent with this prediction. We sought to replicate and extend these findings using a delay of gratification task in rats. The task included a defection response which allowed rats to reverse their preference after choosing a larger-later sucrose reinforcer to instead obtain a smaller-immediate sucrose reinforcer. In Experiment 1, we found that rats would defect on their choice of the larger-later reinforcer, systematically replicating prior research. We also found that experience on the delay of gratification task led to decreases in defection responses. In Experiment 2, we found that prior experience on an intertemporal choice task, with no opportunity to defect, also led to few defection responses on the delay of gratification task. We discuss our findings in the context of whether inhibitory control or temporal learning could be involved in delay of gratification.
Journal of the Experimental Analysis of Behavior, 2022 · doi:10.1002/jeab.767