Belke Terry W, Hancock Stephanie D
Department of Psychology, Mount Allison University, Sackville, New Brunswick, Canada.
J Exp Anal Behav. 2003 Mar;79(2):243-65. doi: 10.1901/jeab.2003.79-243.
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.
将六只雄性白化大鼠置于跑步轮中，并使其接受固定间隔30秒的杠杆按压程序，该程序产生一滴蔗糖溶液或一段固定时长的跑步机会作为强化物。每种强化物类型由不同的刺激信号表示。在实验1中，跑步时长保持在15秒不变，而蔗糖溶液的浓度则在0%、2.5%、5%、10%和15%之间变化。随着浓度降低，在表示蔗糖的刺激信号出现时，强化后停顿时长增加，局部反应速率降低。因此，在表示跑步和蔗糖强化物的刺激信号出现时的反应差异减小，在2.5%时，两种强化物的反应函数相似。在实验2中，蔗糖溶液的浓度保持在15%不变，而跑步机会的时长首先在15秒、45秒和90秒之间变化，随后在5秒、10秒和15秒之间变化。随着跑步时长增加，在表示跑步的刺激信号出现时，强化后停顿时长增加，局部反应速率先增加后降低。总之，当蔗糖浓度和跑步时长都变化时，先前强化物会产生抑制性后效；反应的变化归因于表示两种强化物的刺激信号的兴奋性价值的变化。
