Weatherly JN, Stout JE, Rue HC, Melville CL
McNeese State University, Lake Charles, LA, USA
Behav Processes. 2000 Mar 31;49(1):43-60. doi: 10.1016/s0376-6357(00)00072-3.
The present study investigated whether the sucrose-reinforced lever pressing of rats in the first half of a 50-min session would be sensitive to upcoming food-pellet reinforcement in the second half. In Experiment 1, the type of reinforcer in the first half of the session was always liquid sucrose and type of reinforcer in the second half (liquid sucrose or food pellets) varied across conditions. Sucrose concentration varied across groups (1, 5, or 25%). Results showed that rates and patterns of responding for 1%, and sometimes for 5%, sucrose reinforcers in the first half of the session were higher and steeper, respectively, when food-pellet, rather than sucrose, reinforcement occurred in the second half. Responding for 25% sucrose was not similarly affected. Experiment 2 replicated the results of Experiment 1 using a within-subjects design. Although the present results represent induction (i.e. the opposite of contrast), they are consistent with some results on consummatory contrast. They also further demonstrate that responding on interval schedules of reinforcement can be altered prospectively. By doing so, however, they pose potential problems for current theories for why operant response rates change within the session.
本研究调查了在50分钟实验时段的前半段，大鼠对蔗糖强化杠杆按压的行为是否会对后半段即将出现的食物颗粒强化产生敏感。在实验1中，实验时段前半段的强化物类型始终为液体蔗糖，而后半段的强化物类型（液体蔗糖或食物颗粒）则因条件而异。蔗糖浓度在不同组间有所不同（1%、5%或25%）。结果显示，当实验时段后半段给予食物颗粒而非蔗糖强化时，实验时段前半段1%蔗糖强化物的反应速率以及有时5%蔗糖强化物的反应模式分别更高且更陡峭。对25%蔗糖的反应则未受到类似影响。实验2采用被试内设计重复了实验1的结果。尽管目前的结果代表了诱导（即与对比相反），但它们与一些关于消费性对比的结果一致。它们还进一步证明，基于间隔强化程序的反应可以被前瞻性地改变。然而，这样做给当前关于操作反应率在实验时段内为何变化的理论带来了潜在问题。
