To study how multiple stimuli may control discriminative behavior, we exposed fifteen pigeons to a symbolic matching-to-sample task with three samples that differed only in duration (2, 6, and 18s) and two keylight colors as comparisons. The pigeons learned to choose one comparison after the shortest sample, and the other comparison after the intermediate and longest samples. A 30-s intertrial interval (ITI), illuminated with the houselight, separated the trials. Previous data has suggested that, in this arrangement, both sample keylight and the ITI houselight influence choice. To assess this joint stimulus control, we introduced two tests. In the no-sample test, the keylight was not illuminated and the comparisons followed the ITI immediately; in the dark-ITI test, the houselight was not illuminated. Results confirmed that both stimuli influenced choice, with an apparent trade-off between them: The more a pigeon relied on one stimulus, the less it seemed to rely on the other. We discuss potential models of joint stimulus in temporal discrimination tasks.

为了研究多重刺激如何控制歧视行为，我们让 15 只鸽子接受符号匹配样本任务，其中三个样本仅在持续时间（2、6 和 18 秒）上有所不同，并有两种键光颜色作为比较。鸽子学会了在最短的样本之后选择一个比较，在中间和最长的样本之后选择另一个比较。30 秒的试验间隔 (ITI)，在室内灯光照射下，将试验分开。先前的数据表明，在这种安排中，示例键光和 ITI 室内灯都会影响选择。为了评估这种联合刺激控制，我们引入了两项测试。无样品测试时，键灯不亮，立即按照ITI进行对比；在黑暗-ITI 测试中，室内灯没有点亮。结果证实，两种刺激都会影响选择，它们之间存在明显的权衡：鸽子越依赖一种刺激，它似乎就越不依赖另一种刺激。我们讨论时间辨别任务中联合刺激的潜在模型。