Preston R A
Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, New York 14642.
J Exp Anal Behav. 1994 May;61(3):349-73. doi: 10.1901/jeab.1994.61-349.
In two experiments, rats chose between a standard fixed-duration food-associated stimulus and a stimulus whose duration was the time remaining to reinforcement in an elapsing comparison interval. In Experiment 1, 4 rats responded in a time-left procedure wherein a single initial-link variable-interval schedule set up two potential terminal links simultaneously. As time elapsed in the initial-link schedule, the choice was between a standard fixed-interval 30-s terminal link and a time-left terminal link whose programmed interval requirement equaled 90 s minus the elapsed time in the initial link. Rats generally responded more on the lever with the shortest programmed terminal-link duration, but the temporal parameters of the procedure were found to vary with response distributions. Contrary to previous reports, therefore, time-left data were well predicted by choice models that make no assumptions about animal timing. In Experiment 2, 8 rats responded on a concurrent-chains schedule with independent variable-interval initial links and a time-left terminal link in one of the choice schedules. On the time-left lever, the programmed terminal-link delay equaled 90 s minus the elapsed time in the time-left initial link. On the standard lever, terminal-link responses were reinforced according to a variable-interval schedule whose average value varied over four conditions. Relative time-left initial-link responses increased in the elapsing time-left initial-link schedule as the time-left terminal link became shorter relative to the standard terminal link. Scalar expectancy theory failed to predict the resultant data, but a modified version of the delay-reduction model made good predictions. An analysis of the elaboration of scalar expectancy theory for variable delays demonstrated that the model is poorly formulated for arithmetically distributed delays.
在两项实验中，大鼠在一个标准的固定时长食物关联刺激和一个时长为在逐渐消逝的比较间隔中距强化剩余时间的刺激之间进行选择。在实验1中，4只大鼠在一种剩余时间程序中做出反应，其中一个单一的初始环节可变间隔程序同时设置了两个潜在的终端环节。随着初始环节程序中的时间流逝，选择在一个标准的固定间隔30秒终端环节和一个剩余时间终端环节之间进行，该终端环节设定的间隔要求等于90秒减去初始环节中已流逝的时间。大鼠通常在程序设定的终端环节持续时间最短的杠杆上反应更多，但发现该程序的时间参数会随反应分布而变化。因此，与之前的报告相反，剩余时间数据能被那些不对动物计时做任何假设的选择模型很好地预测。在实验2中，8只大鼠在一个并发链程序上做出反应，其中初始环节为独立的可变间隔，且在其中一个选择程序中有一个剩余时间终端环节。在剩余时间杠杆上，设定的终端环节延迟等于90秒减去剩余时间初始环节中已流逝的时间。在标准杠杆上，终端环节反应根据一个可变间隔程序得到强化，该程序的平均值在四种条件下变化。随着剩余时间终端环节相对于标准终端环节变得更短，在逐渐消逝的剩余时间初始环节程序中，相对的剩余时间初始环节反应增加。标量期望理论未能预测所得数据，但延迟减少模型的一个修改版本做出了很好的预测。对可变延迟的标量期望理论的细化分析表明，该模型对于算术分布延迟的表述不佳。
