Psychology Department, Southern Connecticut State University, New Haven, CT 06515, USA.
J Exp Anal Behav. 2013 Mar;99(2):159-78. doi: 10.1002/jeab.12. Epub 2013 Jan 2.
Twelve pigeons responded on concurrent variable-interval schedules that delivered token stimuli (stimulus lights for some pigeons, and white circles on the response keys for others). During exchange periods, each token could be exchanged for food on a fixed-ratio 1 schedule. Across conditions, the exchange requirements (number of tokens that had to be earned before they could be exchanged for food) varied between one and four for the two response keys. The main findings were that the pigeons' response percentages varied as a function of the number of tokens earned at any given moment, and they were determined by both the delays to food and by the number of food deliveries in the exchange periods. In some conditions, tokens had to be earned but were not visible during the variable-interval schedules for one or both keys. When one key had visible tokens and the other did not, the pigeons showed a preference for the key without visible tokens. A model based on the matching law and a hyperbolic delay-discounting equation could account for the main patterns of choice responding, and for how response percentages changed as successive tokens were earned. The results are consistent with the view that the token stimuli served as discriminative stimuli that signaled the current delays to food.
十二只鸽子在同时进行的可变时距程序中做出反应，该程序会提供代币刺激（对于一些鸽子来说是刺激灯光，对于另一些鸽子来说是响应键上的白色圆圈）。在交换期间，每个代币都可以在固定比率 1 的计划中兑换食物。在不同条件下，两个响应键的交换要求（必须赚取的代币数量才能兑换食物）在 1 到 4 之间变化。主要发现是，鸽子的反应百分比随给定时刻赚取的代币数量而变化，并且受到食物延迟和交换期间的食物交付数量的共同影响。在某些条件下，代币必须赚取，但在一个或两个键的可变时距程序中不可见。当一个键有可见代币而另一个键没有时，鸽子表现出对没有可见代币的键的偏好。基于匹配律和双曲线延迟折扣方程的模型可以解释主要的选择反应模式，以及随着连续代币的赚取，反应百分比如何变化。结果与代币刺激作为信号当前食物延迟的辨别刺激的观点一致。
