University of Minho, Portugal.
J Exp Anal Behav. 2012 May;97(3):263-79. doi: 10.1901/jeab.2012.97-263.
In a temporal double bisection task, animals learn two discriminations. In the presence of Red and Green keys, responses to Red are reinforced after 1-s samples and responses to Green are reinforced after 4-s samples; in the presence of Blue and Yellow keys, responses to Blue are reinforced after 4-s samples and responses to Yellow are reinforced after 16-s samples. Subsequently, given a choice between Green and Blue, the probability of choosing Green increases with the sample duration-the context effect. In the present study we asked whether this effect could be predicted from the stimulus generalization gradients induced by the two basic discriminations. Six pigeons learned to peck Green following 4-s samples (S(+)) but not following 1-s samples (S(-)) and to peck Red following 4-s samples (S(+)) but not following 16-s samples (S(-)). Temporal generalization gradients for Green and Red were then obtained. Finally, the pigeons were given a choice between Green and Red following sample durations ranging from 1 to 16 s. Results showed that a) the two generalization gradients had the minimum at the S(-) duration, an intermediate value between the S(-) and the S(+) durations, and the maximum at the S(+) as well as more extreme durations; b) on choice trials, preference for Green over Red increased with sample duration, the context effect; and c) the two generalization gradients predicted the average context effect well. The Learning-to-Time model accounts for the major trends in the data.
在时间二分任务中，动物学习两种辨别。在红键和绿键存在的情况下，对红键的反应在 1 秒样本后得到强化，对绿键的反应在 4 秒样本后得到强化；在蓝键和黄键存在的情况下，对蓝键的反应在 4 秒样本后得到强化，对黄键的反应在 16 秒样本后得到强化。随后，在绿键和蓝键之间进行选择时，选择绿键的概率随着样本持续时间的增加而增加，即上下文效应。在本研究中，我们想知道这个效应是否可以从两个基本辨别引起的刺激泛化梯度来预测。六只鸽子学会了在 4 秒样本后啄绿键（S(+)）而不是在 1 秒样本后啄绿键（S(-)），以及在 4 秒样本后啄红键（S(+)）而不是在 16 秒样本后啄红键（S(-)）。然后获得了绿键和红键的时间泛化梯度。最后，鸽子在 1 到 16 秒的样本持续时间之间进行绿键和红键之间的选择。结果表明：a）两个泛化梯度在 S(-)持续时间处最小，在 S(-)和 S(+)持续时间之间有一个中间值，在 S(+)以及更极端的持续时间处最大；b）在选择试验中，对绿键的偏好随着样本持续时间的增加而增加，即上下文效应；c）两个泛化梯度很好地预测了平均上下文效应。学习到时间模型解释了数据中的主要趋势。
