Max Planck Institute for Evolutionary Anthropology, D-04103 Leipzig, Germany;
Max Planck Institute for Mathematics in the Sciences, D-04103 Leipzig, Germany.
Proc Natl Acad Sci U S A. 2017 Jul 11;114(28):7462-7467. doi: 10.1073/pnas.1700351114. Epub 2017 Jun 19.
Humans regularly provide others with resources at a personal cost to themselves. Chimpanzees engage in some cooperative behaviors in the wild as well, but their motivational underpinnings are unclear. In three experiments, chimpanzees () always chose between an option delivering food both to themselves and a partner and one delivering food only to themselves. In one condition, a conspecific partner had just previously taken a personal risk to make this choice available. In another condition, no assistance from the partner preceded the subject's decision. Chimpanzees made significantly more prosocial choices after receiving their partner's assistance than when no assistance was given (experiment 1) and, crucially, this was the case even when choosing the prosocial option was materially costly for the subject (experiment 2). Moreover, subjects appeared sensitive to the risk of their partner's assistance and chose prosocially more often when their partner risked losing food by helping (experiment 3). These findings demonstrate experimentally that chimpanzees are willing to incur a material cost to deliver rewards to a conspecific, but only if that conspecific previously assisted them, and particularly when this assistance was risky. Some key motivations involved in human cooperation thus may have deeper phylogenetic roots than previously suspected.
人类经常会以牺牲自己为代价为他人提供资源。黑猩猩在野外也会进行一些合作行为，但它们的动机基础尚不清楚。在三项实验中，黑猩猩总是在一个既能为自己也能为同伴提供食物的选项和一个只能为自己提供食物的选项之间做出选择。在一种情况下，一个同种的同伴之前刚刚冒了个人风险来提供这个选择。在另一种情况下，在主体做出决定之前，没有来自同伴的帮助。与没有提供帮助的情况相比，黑猩猩在得到同伴的帮助后做出更多的亲社会选择（实验 1），而且，至关重要的是，即使选择亲社会的选项对主体来说在物质上是有代价的，情况也是如此（实验 2）。此外，当它们的同伴通过帮助而有失去食物的风险时，主体似乎对同伴的帮助风险很敏感，并且更经常地做出亲社会的选择（实验 3）。这些发现从实验上证明，黑猩猩愿意为同类付出物质代价来提供奖励，但前提是同类之前帮助过它们，尤其是当这种帮助有风险时。一些在人类合作中涉及的关键动机可能比之前怀疑的具有更深的系统发育根源。
