Kanngiesser Patricia, Santos Laurie R, Hood Bruce M, Call Josep
School of Experimental Psychology, University of Bristol, Bristol BS8 1TU, United Kingdom.
J Comp Psychol. 2011 Nov;125(4):436-45. doi: 10.1037/a0024516. Epub 2011 Jul 18.
The endowment effect describes the bias that people often value things that they possess more than things they do not possess. Thus, they are often reluctant to trade items in their possession for items of equivalent value. Some nonhuman primates appear to share this bias with humans, but it remains an open question whether they show endowment effects to the same extent as humans do. We investigated endowment effects in all four great ape species (Pan paniscus, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus) by varying whether apes were endowed with food items (Experiment 1, N = 22) or tools that were instrumental in retrieving food (Experiment 2, N = 23). We first assessed apes' preferences for items of a pair and their willingness to trade items in their possession. We then endowed apes with one item of a pair and offered them to trade for the other item. Apes showed endowment effects for food, but not for tools. In Experiment 3, we endowed bonobos (N = 4) and orangutans (N = 5) with either one or 12 food items. Endowment effects did not differ between species and were not influenced by the number of endowed food items. Our findings suggest that endowment effects in great apes are restricted to immediate food gratification and remain unaffected by the quantity of food rewards. However, endowment effects do not seem to extend to other, nonconsumable possessions even when they are instrumental in retrieving food. In general, apes do not show endowment effects across a range of different commodities as humans typically do.
禀赋效应描述了一种偏差，即人们通常更看重自己拥有的东西，而不是自己没有拥有的东西。因此，他们往往不愿意用自己拥有的物品去交换同等价值的物品。一些非人类灵长类动物似乎与人类有这种偏差，但它们是否与人类表现出相同程度的禀赋效应仍是一个悬而未决的问题。我们通过改变猿类是否被赋予食物（实验1，N = 22）或有助于获取食物的工具（实验2，N = 23），对所有四种大猩猩（倭黑猩猩、黑猩猩、大猩猩、红毛猩猩）的禀赋效应进行了研究。我们首先评估了猿类对一对物品的偏好以及它们交换自己拥有物品的意愿。然后，我们赋予猿类一对物品中的一件，并提出让它们用这件物品去交换另一件。猿类对食物表现出禀赋效应，但对工具没有。在实验3中，我们分别给倭黑猩猩（N = 4）和红毛猩猩（N = 5）赋予1件或12件食物。禀赋效应在不同物种之间没有差异，也不受赋予食物数量的影响。我们的研究结果表明，大猩猩的禀赋效应仅限于即时的食物满足，并且不受食物奖励数量的影响。然而，禀赋效应似乎并不延伸到其他非消耗性物品，即使这些物品有助于获取食物。一般来说，猿类不会像人类通常那样在一系列不同商品上表现出禀赋效应。
