Determinants of reinforcer accumulation during an operant task.
Putting the reinforcer even a few extra steps away makes animals (and probably people) stockpile rewards instead of consuming them right away.
01Research in Context
What this study did
The team placed rats in a box with two levers. One lever earned food pellets. The other lever let the rat pick them up.
The levers sat either side-by-side or far apart. Rats worked on fixed-ratio (FR) schedules or on time-yoked schedules that paid the same total food.
The scientists counted how many pellets piled up before the rat bothered to collect them.
What they found
When the earn and collect levers were far apart, rats let pellets stack up. Nearby levers kept the pile small.
FR schedules made the stash grow even bigger. Adding a progressive-ratio requirement raised the stash again, even though future work got harder.
Distance plus ratio schedules turned rats into pellet savers.
How this fits with other research
Kazdin (1977) and Rilling et al. (1969) showed that time and responses match payoff rates. The new study adds space as a third variable: distance itself becomes a cost that changes how behavior is allocated.
LeBlanc et al. (2003) found that richer FR schedules make behavior stronger and harder to disrupt. Richman et al. (2001) now show the same rich schedules also make rats hoard food, linking schedule size to self-control.
Thrailkill et al. (2018) warned that high reinforcement rates can spark later relapse. The rat data hint at one reason: rich schedules build bigger piles, so more reward waits when conditions change.
Why it matters
Space changes choice. If the payoff for a task sits across the room, clients may let tokens, snacks, or praise accumulate before they walk over. Put the bank or treat jar within arm’s reach and collection rises. When you thin schedules later, start by shortening the walk first; you may see fewer bursts of problem behavior tied to big unpaid caches.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Move the student’s token-exchange jar to the same table as the earn desk and watch how much faster they cash in.
02At a glance
03Original abstract
Responses by rats on an earn lever made available food pellets that were delivered to a food cup by responses on a second, collect, lever. The rats could either collect and immediately consume or accumulate (defined as the percentage of multiple earn responses and as the number of pellets earned before a collect response) earned pellets. In Experiment 1, accumulation varied as a function of variations in the earn or collect response requirements and whether the earn and collect levers were proximal (31 cm) or distal (248 cm) to one another. Some accumulation occurred under all but one of the conditions, but generally was higher when the earn and collect levers were distal to one another, particularly when the earn response requirement was fixed-ratio (FR) 1. In Experiment 2, the contributions of responses and time to accumulation were assessed by comparing an FR 20 earn response requirement to a condition in which only a single earn response was required at the end of a time interval nominally yoked to the FR interval. When 248 cm separated the earn and collect levers, accumulation was always greater in the FR condition, and it was not systematically related to reinforcement rate. In Experiment 3, increasing the earn response requirement with a progressive-ratio schedule that reset only with a collect response increased the likelihood of accumulation when the collect and earn levers were 248 cm apart, even though such accumulation increased the next earn response requirement. Reinforcer accumulation is an understudied dimension of operant behavior that relates to the analysis of such phenomena as hoarding and self-control, in that they too involve accumulating versus immediately collecting or consuming reinforcers.
Journal of the experimental analysis of behavior, 2001 · doi:10.1901/jeab.2001.76-321