Satiation, capacity, and within-session responding.
Individual satiation capacity predicts how fast responding declines within a session—measure it to tailor reinforcement schedules.
01Research in Context
What this study did
Carmichael et al. (1999) watched pigeons peck a key during long sessions. They first measured how much grain each bird could hold in its crop. Then they ran daily VI sessions and plotted how pecking slowed minute by minute.
Some birds got extra food before the session started. The team asked: does a small-capacity bird satiate faster and quit sooner?
What they found
Birds with smaller crop capacity did satiate faster. Their peck rate dropped off more steeply within the same hour. Prefeeding made the drop even steeper for these birds.
Larger-capacity birds kept pecking longer before slowing down.
How this fits with other research
McSweeney et al. (2000) contradicts the story. They say the drop is not about a full stomach. It is about habituation to the light and key. Both papers see the same downward curve, but they name different causes.
Frost et al. (1996) extends the idea. They showed that bigger pellets keep pecking stronger. Taken together, pellet size and stomach size both shape how long motivation lasts.
Eugenia Gras et al. (2003) add a human twist. With noncontingent reinforcement, larger or longer snacks suppress responding. The same satiation logic applies outside the pigeon lab.
Why it matters
Check your learner’s "stomach size" before you pick a schedule. A child who eats a big lunch may satiate faster during token work. Start with smaller or shorter reinforcers and watch the within-session curve. If responding dives early, shorten the session or thin the schedule instead of blaming attention.
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02At a glance
03Original abstract
Responding may change substantially over the course of a session (McSweeney, Hinson, & Cannon, 1996). The role of satiation in this effect was investigated in three experiments. Experiment 1 showed that the capacity of pigeons to consume milo over a 1-hr period was relatively stable across three different methods of measurement. In Experiment 2, pigeons were divided into two groups that differed in their capacity based on one of those measures. Key pecking was then reinforced under a variable-interval 30-s schedule with hopper durations of 2 or 5 s. According to the satiation hypothesis, subjects with small capacities should satiate faster and therefore show greater decreases in food-reinforced responding than would subjects with larger capacities. The results confirmed this prediction and showed that the magnitudes of within-session decreases were better predicted by the amount an animal consumed relative to its capacity than by absolute amount alone. In Experiment 3, each pigeon was prefed 0, 5, 15, or 25 g of milo prior to each session. Consistent with the satiation hypothesis, increases in prefeeding produced lower overall response rates in the smaller capacity subjects than in the larger capacity subjects at each level of prefeeding. These experiments demonstrate the importance of a new variable in the control of behavior, and provide a recommended technique for its measurement.
Journal of the experimental analysis of behavior, 1999 · doi:10.1901/jeab.1999.72-407