School of Psychology, St Andrews University, , St Andrews, UK.
Proc Biol Sci. 2013 Jan 23;280(1755):20122765. doi: 10.1098/rspb.2012.2765. Print 2013 Mar 22.
Animals that maintain cooperative relationships show gains in longevity and offspring survival. However, little is known about the cognitive or hormonal mechanisms involved in cooperation. Indeed, there is little support for a main hypothesis that non-human animals have the cognitive capacities required for bookkeeping of cooperative exchanges. We tested an alternative hypothesis that cooperative relationships are facilitated by an endocrinological mechanism involving oxytocin, a hormone required for bonding in parental and sexual relationships across mammals. We measured urinary oxytocin after single bouts of grooming in wild chimpanzees. Oxytocin levels were higher after grooming with bond partners compared with non-bond partners or after no grooming, regardless of genetic relatedness or sexual interest. We ruled out other possible confounds, such as grooming duration, grooming direction or sampling regime issues, indicating that changes in oxytocin levels were mediated by social bond strength. Oxytocin, which is thought to act directly on neural reward and social memory systems, is likely to play a key role in keeping track of social interactions with multiple individuals over time. The evolutionary linkage of an ancestral hormonal system with complex social cognition may be the primary mechanism through which long-term cooperative relationships develop between both kin and non-kin in mammals.
维持合作关系的动物在寿命和后代存活率方面都有获益。然而，人们对合作涉及的认知或激素机制知之甚少。实际上，几乎没有证据支持这样一个主要假设，即非人类动物具有进行合作交换记账所需的认知能力。我们测试了一个替代假设，即合作关系是由涉及催产素的内分泌机制促进的，催产素是哺乳动物中亲子关系和性关系所必需的激素。我们测量了野生黑猩猩单次梳理后的尿液中的催产素水平。与非伴侣或不梳理相比，与伴侣梳理后，催产素水平更高，而不管遗传关系或性兴趣如何。我们排除了其他可能的混杂因素，例如梳理持续时间、梳理方向或采样方案问题，这表明催产素水平的变化是由社交纽带强度介导的。催产素被认为直接作用于神经奖励和社会记忆系统，它可能在随着时间的推移跟踪与多个个体的社交互动方面发挥关键作用。具有复杂社会认知能力的祖先进化激素系统的进化联系可能是哺乳动物中亲族和非亲族之间长期合作关系发展的主要机制。
