Across various species, infant faces share various features referred to as "baby schema"(Lorenz, 1942). Assuming that these features are indeed shared among species, it is possible that nonhuman animals may perceive age information in conspecific and heterospecific faces. We tested whether tufted capuchin monkeys (Sapajus apella) would visually categorize age from faces. In Experiment 1, we trained 4 monkeys to discriminate adult and infant faces of conspecifics using a symbolic matching-to-sample procedure. We then tested whether their categorization transferred to faces of other species (i.e., dogs and humans). In Experiment 2, we trained another 2 monkeys on age categorization of heterospecific (human) faces and tested them with conspecific and dog faces, to assess whether conspecific age categorization in Experiment 1 was specific. In Experiment 3, the 4 monkeys from Experiment 1 were trained with human faces, whereas the 2 monkeys from Experiment 2 were trained with conspecific faces; we then tested all 6 monkeys with faces of dogs and other species including New World monkeys, Old World monkeys, apes, and carnivores. During training, the monkeys quickly learned to categorize adult and infant faces of both conspecifics and humans. However, age categorization failed to transfer to different species in the test phase in all 3 experiments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

中文翻译：

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卷尾猴（Sapajus apella）中同种和异种面孔的年龄分类。

在各种各样的物种中，婴儿的面孔具有被称为“婴儿图式”的各种特征（Lorenz，1942年）。假设这些特征确实在物种之间共享，那么非人类动物可能会在同种和异种面孔中感知年龄信息。我们测试了簇绒的卷尾猴（Sapajus apella）是否会从面孔上对年龄进行视觉分类。在实验1中，我们训练了4只猴子，使用符号匹配到样本的程序来区分特定物种的成年和婴儿面孔。然后，我们测试了它们的分类是否转移到其他物种（例如狗和人）的脸上。在实验2中，我们对另外2只猴子进行了异种（人）脸的年龄分类训练，并用同种和狗脸进行了测试，以评估实验1中的同种年龄分类是否具有特异性。在实验3中，对实验1的4只​​猴子进行了人脸训练，而实验2的2只猴子进行了特定的脸部训练。然后，我们用狗和其他物种（包括新世界猴子，旧世界猴子，猿猴和食肉动物）的脸对所有6只猴子进行了测试。在训练过程中，猴子很快学会了对同种动物和人类的成年和婴儿面孔进行分类。但是，在所有3个实验的测试阶段，年龄分类都未能转移到不同的物种。（PsycINFO数据库记录（c）2019 APA，保留所有权利）。和食肉动物。在训练过程中，猴子很快学会了对同种动物和人类的成年和婴儿面孔进行分类。但是，在所有3个实验的测试阶段，年龄分类都未能转移到不同的物种。（PsycINFO数据库记录（c）2019 APA，保留所有权利）。和食肉动物。在训练过程中，猴子很快学会了对同种动物和人类的成年和婴儿面孔进行分类。但是，在所有3个实验的测试阶段，年龄分类都未能转移到不同的物种。（PsycINFO数据库记录（c）2019 APA，保留所有权利）。