Responding for sucrose and wheel-running reinforcement: effects of sucrose concentration and wheel-running reinforcer duration.
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.
Belke
Terry W
TW
Department of Psychology, Mount Allison University, Sackville, New Brunswick, Canada. tbelke@mta.ca
Hancock
Stephanie D
SD
D000818:Animals; D007266:Inhibition, Psychological; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012054:Reinforcement, Psychology; D012420:Running; D013395:Sucrose / Q000008:administration & dosage*; D013997:Time Factors
D013395:Sucrose