Weatherly Jeffrey N., Tischart Lindsey M., Palbicki Janel
Department of Psychology, University of North Dakota, 58202-8380, Grand Forks, ND, USA
Behav Processes. 2003 Aug 29;64(1):113-120. doi: 10.1016/s0376-6357(03)00128-1.
Research has demonstrated that rats increase their rate of lever pressing for sucrose reinforcement when food-pellet reinforcement will soon be available within the session. Recent results suggest that this increase occurs because stimuli in the session come to signal different levels of overall reinforcement. The present experiment tested this idea by having rats respond in two types of session. In one, they pressed lever A for 1% sucrose reinforcers in the first half of the session and lever B for food-pellet reinforcers in the second half (the opposing lever was retracted in the respective half). In the other, they pressed lever B for 1% sucrose reinforcers in the first half and lever A for 1% sucrose reinforcers in the second. Thus, the presence of lever A in the first half of the session was predictive of upcoming food-pellet reinforcement, but only lever B was ever used to obtain food pellets. Subjects responded at a higher rate on lever B in the first half of the session than on lever A, despite food-pellet reinforcement being unavailable in such sessions. Furthermore, they responded at a higher rate on lever B during probe sessions in which both levers were available. These results demonstrate that stimulus control over induction occurs when a stimulus becomes differentially associated with a heightened level of reinforcement. However, questions remain as to whether this association is Pavlovian or whether stimuli with "predictive value" may ever lead to induction.
研究表明，当在实验过程中很快就能获得食物颗粒强化时，大鼠按压杠杆以获取蔗糖强化的速率会增加。最近的结果表明，这种增加的发生是因为实验过程中的刺激开始预示着不同水平的总体强化。本实验通过让大鼠在两种类型的实验过程中做出反应来检验这一观点。在一种实验过程中，它们在前半段实验中按压杠杆A以获取1%的蔗糖强化物，在后半段实验中按压杠杆B以获取食物颗粒强化物（相应的另一半实验中，相对的杠杆会缩回）。在另一种实验过程中，它们在前半段实验中按压杠杆B以获取1%的蔗糖强化物，在后半段实验中按压杠杆A以获取1%的蔗糖强化物。因此，实验前半段杠杆A的存在预示着即将到来的食物颗粒强化，但只有杠杆B曾被用于获取食物颗粒。尽管在这样的实验过程中无法获得食物颗粒强化，但实验对象在前半段实验中对杠杆B的反应速率高于对杠杆A的反应速率。此外，在两个杠杆都可用的探测实验过程中，它们对杠杆B的反应速率更高。这些结果表明，当一种刺激与更高水平的强化产生差异关联时，刺激对诱导的控制就会发生。然而，关于这种关联是否是巴甫洛夫式的，或者具有“预测价值”的刺激是否可能导致诱导，仍然存在疑问。
