Responding for sucrose and wheel-running reinforcement: effects of sucrose concentration and wheel-running reinforcer duration.
Larger reinforcers, whether sweet or physical, make learners pause longer before the next response.
01Research in Context
What this study did
The team asked: does the size of a reinforcer change how long a rat waits before pressing again? They used two kinds of pay-offs: sweet water and time on a running wheel.
Rats pressed a lever on a fixed-interval schedule. Sometimes the sugar water was weak, sometimes strong. Sometimes the wheel spun for a short time, sometimes long. The scientists watched how long each rat paused after every treat.
What they found
Bigger reinforcers made the rats wait longer. Weak sugar or short wheel spins let the rats start pressing again sooner. Strong sugar or long runs created longer post-reinforcement pauses.
The effect showed up in both pause time and the speed of pressing right after the pause. Reinforcer type and size worked together to brake or boost the next burst of responses.
How this fits with other research
Storm (2000) had already seen that longer wheel time stretched the pause, but only when the change happened inside the same session. The new study widens the lens by comparing two very different rewards across sessions.
Glover et al. (1976) found the same pause-lengthening on variable-ratio schedules using food concentration. Fisher et al. (2003) now show the rule also holds on fixed-interval schedules and with wheel running, tying the pause effect to reinforcer size, not schedule type.
Bromley et al. (1998) showed short gaps between food could shorten future pauses. W et al. add that the reinforcer itself, not just its timing, can lengthen or shorten the pause.
Why it matters
When you thin schedules or swap reinforcers, remember that bigger or longer pay-offs will slow the learner’s return to work. If you need rapid responding, use smaller or briefer rewards. If you want to build patience, offer a richer reinforcer and expect a longer pause.
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02At a glance
03Original abstract
Six male albino rats were placed in running wheels and exposed to a fixed-interval 30-s schedule of lever pressing that produced either a drop of sucrose solution or the opportunity to run for a fixed duration as reinforcers. Each reinforcer type was signaled by a different stimulus. In Experiment 1, the duration of running was held constant at 15 s while the concentration of sucrose solution was varied across values of 0, 2.5. 5, 10, and 15%. As concentration decreased, postreinforcement pause duration increased and local rates decreased in the presence of the stimulus signaling sucrose. Consequently, the difference between responding in the presence of stimuli signaling wheel-running and sucrose reinforcers diminished, and at 2.5%, response functions for the two reinforcers were similar. In Experiment 2, the concentration of sucrose solution was held constant at 15% while the duration of the opportunity to run was first varied across values of 15, 45, and 90 s then subsequently across values of 5, 10, and 15 s. As run duration increased, postreinforcement pause duration in the presence of the wheel-running stimulus increased and local rates increased then decreased. In summary, inhibitory aftereffects of previous reinforcers occurred when both sucrose concentration and run duration varied; changes in responding were attributable to changes in the excitatory value of the stimuli signaling the two reinforcers.
Journal of the experimental analysis of behavior, 2003 · doi:10.1901/jeab.2003.79-243