Grace Randolph C, Bragason Orn
University of Canterbury, Department of Psychology, Private Bag 4800, Christchurch, New Zealand.
J Exp Anal Behav. 2005 Mar;83(2):169-84. doi: 10.1901/jeab.2005.28-04.
Our research addressed the question of whether sensitivity to relative reinforcer magnitude in concurrent chains depends on the distribution of reinforcer delays when the terminal-link schedules are equal. In Experiment 1, 12 pigeons responded in a two-component procedure. In both components, the initial links were concurrent variable-interval 40-s variable-interval 40-s, and the terminal links were both 20-s interval schedules in which responses were reinforced by either 4-s of grain in one, or 2-s of grain in the other. The only difference between the components was whether the terminal-link schedules were fixed interval or variable intervals. For all subjects, the relative rate of responding in the initial links for the terminal link that produced the 4-s reinforcer was greater when the terminal links were fixed-interval schedules than when they were variable-interval schedules. This result is contrary to the prediction of Grace's (1994) contextual choice model, but is consistent with both Mazur's (2001) hyperbolic value-added model and Killeen's (1985) incentive theory. In Experiment 2, 4 pigeons responded in a concurrent-chains procedure in which 4-s or 2-s reinforcers were provided independently of responding according to equal fixed-time or mixed-time schedules. Preference for the 4-s reinforcer increased as the variability of the intervals comprising the mixed-time schedules was decreased. Generalized-matching sensitivity of initial-link response allocation to relative reinforcer magnitude was proportional to the geometric mean of the terminal-link delays.
我们的研究探讨了在终端链时间表相等的情况下，并发链中对相对强化物大小的敏感性是否取决于强化物延迟的分布。在实验1中，12只鸽子在一个两成分程序中做出反应。在两个成分中，初始链都是并发可变间隔40秒-可变间隔40秒，终端链都是20秒间隔时间表，其中一个时间表中4秒的谷物强化反应，另一个时间表中2秒的谷物强化反应。两个成分之间的唯一区别是终端链时间表是固定间隔还是可变间隔。对于所有受试者，当终端链是固定间隔时间表时，产生4秒强化物的终端链在初始链中的相对反应率高于可变间隔时间表时。这一结果与格雷斯（1994）的情境选择模型的预测相反，但与马祖尔（2001）的双曲线增值模型和基林（1985）的激励理论一致。在实验2中，4只鸽子在一个并发链程序中做出反应，其中根据相等的固定时间或混合时间时间表独立于反应提供4秒或2秒的强化物。随着构成混合时间时间表的间隔的变异性降低，对4秒强化物的偏好增加。初始链反应分配对相对强化物大小的广义匹配敏感性与终端链延迟的几何平均值成正比。
