Effects of increment size and reinforcer volume on progressive ratio performance.
Bigger reinforcers and larger ratio steps can push higher breaking points, yet easy steps plus big food can satiate and stop responding.
01Research in Context
What this study did
CUMMINBOWER et al. (1963) asked rats to press a lever for food. Each time the rat met a ratio, the next ratio got bigger. The team changed two things: how fast the ratio grew and how big each food pellet was. They watched how far the rat would go before it quit—the breaking point.
What they found
Big jumps in the ratio and big pellets let rats climb to higher ratios before stopping. But there was a twist. When the ratio grew slowly and the pellet was large, rats slowed down and sometimes quit early. Too much food plus easy steps created satiation, not motivation.
How this fits with other research
Reed et al. (1988) later saw the same double effect on fixed VR schedules: larger food increased response speed but also lengthened pauses. The food-size rule held across setups.
Foltin (1997) flipped the story. When longer wheel-running time served as the reinforcer, more access reduced lever pressing. Bigger was worse, not better. The difference is reinforcer type: food versus activity.
Lowe et al. (1974) showed the schedule matters too. Large pellets sped up responding only on interval schedules, not all ratio schedules. Magnitude helps only in the right context.
Why it matters
For BCBAs, the lesson is to balance size and step. A child may work harder for a larger edible, but pair it with small ratio jumps to avoid rapid satiation. If the reinforcer is an activity like iPad time, longer access may kill later responding, so keep it short. Always watch for the moment motivation turns into fullness or boredom.
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02At a glance
03Original abstract
The progressive ratio schedule requires the subject to emit an increasing number of responses for each successive reinforcement. Eventually, the response requirement becomes so large that the subject fails to respond for a period of 15 min and thereby terminates the session. This point is arbitrarily defined as the "breaking point" of the subject's performance. The measure is quantified in terms of the number of responses in the final completed (i.e., reinforced) ratio run of the session. Previous work has shown that this measure varies as a function of several motivational variables and may thus be useful as an index of reinforcement strength. The present study is an extension of that work. The subjects were four rats. In the first experiment, the effects of the size of the increment by which each ratio run increased were studied. In two additional experiments, the volume of a liquid reinforcer was varied using both large and small ratio increments. The results indicate that the number of responses in the final completed ratio run increases as a function of the size of the ratio increment. However, the number of reinforcements obtained by the animals per session declines sharply. When large ratio increments are used, the number of responses in the final ratio increases as a function of the volume of the reinforcer, but when small increments are used, progressive satiation results in a decline in performance with the larger volumes of liquid.
Journal of the experimental analysis of behavior, 1963 · doi:10.1901/jeab.1963.6-387