A goal of the comparative approach is to test a variety of species on the same task. Here, we examined whether the factors that helped capuchin monkeys improve their performance in a dichotomous choice task would generalize to three other primate species: orangutans, gorillas, and drill monkeys. In this task, subjects have access to two options, each resulting in an identical food, but one (the ephemeral option) is only available if it is chosen first, whereas the other one (the permanent option) is always available. Therefore, the food‐maximizing solution is to choose the ephemeral option first, followed by the permanent option for an additional reward. On the original version (plate task), the options were discriminated by the color and pattern of the plates holding the food, while on two subsequent versions we used altered cues that we predicted would improve performance: (1) the color of the foods themselves (color task), which we hypothesized was relevant to primates, who choose foods rather than substrates on which foods are found when foraging, and (2) patterned cups covering the foods (cup task), which we hypothesized would help primates avoid the prepotent response associated with visible food. Like capuchins, all three species initially failed to solve the plate task. However, while orangutans improved their performance from the plate to the color task, they did not for the cup task, and only a few gorillas and no drills succeeded in either task. Unfortunately, our ability to interpret these data was obscured by differences in the subjects' level of experience with cognitive testing and practical constraints that precluded the use of completely identical procedures across species. Nonetheless, we consider what these results can tell us, and discuss the value of conducting studies across multiple sites despite unavoidable differences.

中文翻译：

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猩猩（Pongo spp。），大猩猩（Gorilla gorilla gorilla）和钻（Mandrillus leucophaeus）在临时觅食任务中的比较性能

比较方法的目标是在同一任务上测试各种物种。在这里，我们研究了帮助卷尾猴在二分法选择任务中提高其性能的因素是否会推广到其他三种灵长类动物：猩猩，大猩猩和钻猴。在此任务中，受试者可以使用两个选项，每个选项都产生相同的食物，但是只有首先选择一个选项，一个选项（临时选项）才可用，而另一个选项（永久选项）始终可用。因此，食物最大化的解决方案是首先选择临时选项，然后再选择永久选项以获得额外奖励。在原始版本（印版任务）上，选项是根据盛有食物的印版的颜色和图案来区分的，而在随后的两个版本中，我们使用了改变的线索，我们预测它们会改善性能：（1）我们假设的食物本身的颜色（颜色任务）与灵长类动物有关，灵长类动物选择食物而不是发现食物时发现食物的基质觅食，以及（2）图案覆盖食物的杯子（杯子任务），我们认为这将有助于灵长类动物避免与可见食物相关的有力反应。像卷尾猴一样，这三个物种最初都未能解决板任务。但是，虽然猩猩将其性能从印版提高到了上色任务，但他们并没有完成杯赛任务，在这两项任务中只有少数大猩猩并且没有演习。不幸的是，我们对这些数据的解释能力被受试者的差异所掩盖。认知测试和实践限制的经验水平，从而无法跨物种使用完全相同的程序。尽管如此，我们考虑了这些结果可以告诉我们的内容，并讨论了尽管存在不可避免的差异，但在多个地点进行研究的价值。