Zimmermann Felizitas, Zemke Franziska, Call Josep, Gómez Juan Carlos
Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
Anim Cogn. 2009 Mar;12(2):347-58. doi: 10.1007/s10071-008-0194-8. Epub 2008 Oct 24.
Although pointing is not part of great apes' natural gestural repertoire, they can learn to point to food, in order to request it. To assess the flexibility with which they can use this gesture, one can vary the potential referent of the point. In two previous studies, three orangutans (two of them human-reared) have shown the ability to point to the location of a tool which a human experimenter needed in order to give them food. Here, we tested six orangutans and five bonobos using a set-up in which our subjects had to guide a human experimenter to the hiding place of a fork which was needed in order to retrieve a piece of food for the subject out of a vertical tube. We further examined the potential role of a competitive/deceptive context by varying the identity of the person responsible for hiding the tool. In addition, we implemented three different control conditions in which an object was hidden but it was not necessary to indicate its location to get the food. We found that the majority of subjects spontaneously guided the experimenter to the hiding place of the fork by pointing to it when it was necessary and they did so significantly less in control conditions. We did not find an effect of the person hiding the fork. Our results show that mother-reared orangutans and bonobos are able to point to inform a human about the location of an object that the human needs to procure food for the subject and that they can take into account whether it is relevant or not to do so.
尽管指物并非大猩猩自然手势语库的一部分,但它们能够学会指向食物以获取食物。为了评估它们使用这种手势的灵活性,可以改变指物的潜在指代对象。在之前的两项研究中,三只猩猩(其中两只由人类抚养长大)已表现出能够指向人类实验者获取食物所需工具的位置。在此,我们使用一种设置对六只猩猩和五只倭黑猩猩进行了测试,在该设置中,我们的实验对象必须引导人类实验者找到一把叉子的隐藏位置,以便从垂直管中为实验对象取出一块食物。我们通过改变负责隐藏工具的人的身份,进一步研究了竞争/欺骗情境的潜在作用。此外,我们实施了三种不同的对照条件,在这些条件下,一个物体被隐藏起来,但无需指明其位置就能获取食物。我们发现,大多数实验对象在有必要时会自发地通过指向叉子的隐藏位置来引导实验者,而在对照条件下这样做的次数明显减少。我们没有发现隐藏叉子的人的身份产生影响。我们的研究结果表明,由母亲抚养长大的猩猩和倭黑猩猩能够通过指物告知人类获取食物所需物体的位置,并且它们能够考虑这样做是否相关。