Weatherly Jeffrey N, Nurnberger Jeri T, Kristiansen-Moen Lisa A
Department of Psychology, University of North Dakota, Grand Forks, ND 58202-8380, USA.
Behav Processes. 2006 Sep;73(2):156-63. doi: 10.1016/j.beproc.2006.05.002. Epub 2006 May 12.
Rats increase their rate of operant responding for 1% sucrose reinforcement in the first half of an experimental session if a high-valued reinforcer will be available in the second half. Previous research suggests that this induction effect occurs because the reinforcing value of the low-valued substance has increased. The present study investigated whether this increase may occur because of where the substances are delivered. Rats pressed a lever to earn 1% liquid-sucrose reinforcers in the first half of the session. In control conditions, they also pressed for 1% sucrose in the second half. In treatment conditions, they pressed for food-pellet (Experiment 1) or 32% sucrose (Experiment 2) reinforcers in the second half, with these reinforcers either being delivered to the same location as the 1% sucrose or to a different location. Upcoming food-pellet or 32% sucrose reinforcement increased rates of lever pressing for 1% sucrose in the first half of the session, with the largest increase observed when the high-valued reinforcer was delivered to the same location as the 1% sucrose. Qualitatively similar results were found with rates of consumption of 1% sucrose reinforcers in the first half of the session, which were measured in Experiment 2. The location to which reinforcers are delivered appears to be one of the factors that contributes to this induction effect. The present results may therefore identify one of the factors that determine whether differential conditions of reinforcement will lead to contrast or induction.
如果在实验时段的后半段会有高价值强化物，大鼠会在该时段的前半段提高对1%蔗糖强化物的操作性反应速率。先前的研究表明，这种诱导效应的发生是因为低价值物质的强化价值增加了。本研究调查了这种增加是否可能是由于物质的投放位置所致。大鼠在实验时段的前半段按压杠杆以获取1%的液体蔗糖强化物。在对照条件下，它们在实验时段的后半段也按压杠杆以获取1%的蔗糖。在处理条件下，它们在实验时段的后半段按压杠杆以获取食物颗粒（实验1）或32%蔗糖（实验2）强化物，这些强化物要么被投放到与1%蔗糖相同的位置，要么投放到不同的位置。即将到来的食物颗粒或32%蔗糖强化物增加了实验时段前半段大鼠对1%蔗糖的杠杆按压速率，当高价值强化物被投放到与1%蔗糖相同的位置时，观察到的增加幅度最大。在实验2中测量的实验时段前半段1%蔗糖强化物的消耗速率也发现了定性相似的结果。强化物的投放位置似乎是促成这种诱导效应的因素之一。因此，本研究结果可能确定了决定不同强化条件是否会导致对比或诱导的因素之一。
