The understanding that the perceptual appearance of the environment can differ in several ways from the reality underlies the ability to discriminate appearance from reality. Being able to realize when a misperception can lead us to behave in inappropriate ways confers an evolutionary advantage and may be a prerequisite to develop a Theory of Mind. Understanding that our own perception can differ from reality seems indeed necessary to attribute to others perceptions or beliefs different than ours. This appearance-reality discrimination ability has recently been demonstrated in great apes but no information is currently available regarding this ability in other nonhuman species. In a comparative study, we tested Tonkean macaques (Macaca tonkeana), an Old World primate species, and brown capuchins (Sapajus apella), a New World primate species. We provided monkeys with two experiments using visual illusions of size and quantity to test their ability to discriminate appearance from reality, with an experimental setup similar to the one developed by Krachun et al. (2016) on chimpanzees. A large number of brown capuchins, from different ages and both sexes, as well as two Tonkean macaques succeeded in the two experiments. By ruling out all alternative explanations (i.e. visual tracking or associative learning), our study brings the first evidence that some Old World and New World monkeys are able to discriminate appearance from reality. Our results suggest moving the evolutionary apparition of this cognitive ability earlier in time. Finally, it suggests that humans could share more Theory of Mind components with more nonhuman species than we previously thought.

中文翻译：

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猴子能够分辨外表与现实吗？

对环境的感知外观可能与现实有几种不同的理解，这是区分外观与现实的能力的基础。能够意识到何时会产生误解，会导致我们以不适当的方式行事，从而赋予我们进化上的优势，这可能是发展心智理论的先决条件。理解我们自己的感知可能与现实不同似乎确实有必要将其归因于与我们不同的其他感知或信念。最近在大猿猴中已经证实了这种外观真实性辨别能力，但是目前尚无其他非人类物种有关此能力的信息。在一项比较研究中，我们测试了旧世界灵长类动物的Tonkean猕猴（Macaca tonkeana）和新世界灵长类动物的棕色卷尾猴（Sapajus apella）。我们用大小和数量的视觉幻觉为猴子提供了两个实验，以测试它们区分外观与现实的能力，实验设置类似于Krachun等人开发的实验设置。（2016）在黑猩猩上。在两个实验中，成功地获得了来自不同年龄和性别的大量棕色卷尾猴以及两只Tonkean猕猴。通过排除所有其他解释（例如，视觉跟踪或联想学习），我们的研究提供了第一个证据，表明某些旧大陆和新大陆猴子能够将外表与现实区分开。我们的研究结果表明，应在更早的时候改变这种认知能力的进化论。最后，它表明人类可以比我们以前认为的更多地与更多非人类物种共享更多的理论理论成分。