Effects of variations in local reinforcement rate on local response rate in variable interval schedules.
On a VI schedule, learners speed up where food is more likely and pause longer when the next reinforcer is initially improbable.
01Research in Context
What this study did
The team watched pigeons peck a key on a variable-interval (VI) schedule.
They changed how soon the next food could pop up right after each pellet.
Then they counted pecks in tiny slices of time to see if the birds sped up or slowed down.
What they found
Birds pecked fastest in the spots where food odds were highest.
Right after a pellet, if the next food was unlikely, the birds took long breaks.
In short, local response rate tracked local reinforcement probability moment to moment.
How this fits with other research
Thomas (1968) first broke overall rate into pieces; Leslie (1981) shows those pieces shift with VI probability.
Williams (1971) looked at concurrent FI/VI and found choice followed a power curve; Leslie (1981) zooms inside a single VI to show why that curve bends—reinforcement odds move the peeps.
Mahoney et al. (1971) used cyclic intervals and saw pauses grow with upcoming wait time; Leslie (1981) finds the same pause rule inside ordinary VI schedules, no cycle needed.
Rapport et al. (1996) later added concurrent VI data; they confirm that sensitivity to local rate still drives choice when two schedules sit side by side.
Why it matters
When you shape or thin a VI schedule, remember the animal feels the local odds.
If reinforcement is scarce right after a reinforcer, expect long pauses—don’t label the learner as unmotivated.
To keep response flow, seed richer reinforcement moments early in the interval or add brief cues that signal “food odds rising.”
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Join Free →After each reinforcer, drop a quick probe response; if the pause stretches, insert an early tiny reinforcer or brief stimulus to reset local probability.
02At a glance
03Original abstract
Rats trained to lever press for sucrose were exposed to variable-interval schedules in which (i) the probability of reinforcement in each unit of time was a constant, (ii) the probability was high in the first ten seconds after reinforcement and low thereafter, (iii) the probability was low for ten seconds and high thereafter, (iv) the probability increased with time since reinforcement, or (v) the probability was initially zero and then increased with time since reinforcement. All schedules generated similar overall reinforcement rates. A peak in local response rate occurred several seconds after reinforcement under those schedules where reinforcement rate at this time was moderate or high ([i], [ii], and [iv]). Later in the inter-reinforcement interval, local response rate was roughly constant under those schedules with a constant local reinforcement rate ([i], [ii], and [iii]), but increased steadily when local reinforcement rate increased with time since reinforcement ([iv] and [v]). Postreinforcement pauses occurred on all schedules, but were much longer when local reinforcement rate was very low in the ten seconds after reinforcement ([iii]). The interresponse time distribution was highly correlated with the distribution of reinforced interresponse times, and the distribution of postreinforcement pauses was highly correlated with the distribution of reinforced postreinforcement pauses on some schedules. However, there was no direct evidence that these correlations resulted from selective reinforcement of classes of interresponse times and pauses.
Journal of the experimental analysis of behavior, 1981 · doi:10.1901/jeab.1981.35-45