Data from: Marmoset monkeys evaluate third-party reciprocity

Many nonhuman primates have been observed to reciprocate and to understand reciprocity in one-to-one social exchanges. A recent study demonstrated that capuchin monkeys are sensitive to both third-party reciprocity and violation of reciprocity; however, whether this sensitivity is a function of general intelligence, evidenced by their larger brain size relative to other primates, remains unclear. We hypothesized that primates with highly pro-social traits are sensitive to others’ reciprocity, even with a relatively smaller brain size. Here, we show that common marmosets discriminated between human actors who reciprocated in social exchanges with others and those who did not. Monkeys accepted rewards less frequently from non-reciprocators than they did from reciprocators when the non-reciprocators had retained all food items, but they accepted rewards from both actors equally when they had observed reciprocal exchange between the actors. These results suggest that mechanism to detect unfair reciprocity in third-party social exchanges do not occur due to a domain-free higher cognitive ability based on proportionally larger brains, but rather, that this is derived from the co-operative and pro-social tendencies of the species, suggesting multiple evolutions in primate lineage.

已有研究观察到，诸多非人灵长类动物会进行互惠行为，并能理解一对一社会互动中的互惠逻辑。近期一项研究表明，卷尾猴对第三方互惠及互惠违背行为均具备感知能力；但该感知能力是否源于其相较于其他灵长类更大脑容量所体现出的一般智力，目前仍不明确。本研究提出假设：即便脑容量相对较小，具备高度亲社会特质的灵长类动物，也能感知他者的互惠行为。本研究结果显示，普通狨猴能够区分在社会互动中表现出互惠行为与未表现出互惠行为的人类互动者。当非互惠者留存了全部食物时，狨猴从非互惠者处接受奖励的频次显著低于互惠者；但当狨猴观察到互动双方存在互惠行为时，它们对两类互动者的奖励接受度并无差异。上述结果表明，灵长类检测第三方社会互动中不公平互惠行为的机制，并非源于基于相对更大脑容量的无领域限制高级认知能力；相反，该机制源自该物种的合作与亲社会倾向，这提示灵长类演化谱系中存在多种独立演化路径。