Hauser Marc D, Chen M Keith, Chen Frances, Chuang Emmeline
Department of Psychology, and Programme in Neurosciences, Harvard University, Cambridge, MA 02138, USA.
Proc Biol Sci. 2003 Nov 22;270(1531):2363-70. doi: 10.1098/rspb.2003.2509.
Altruistic food giving among genetically unrelated individuals is rare in nature. The few examples that exist suggest that when animals give food to unrelated others, they may do so on the basis of mutualistic or reciprocally altruistic relationships. We present the results of four experiments designed to tease apart the factors mediating food giving among genetically unrelated cotton-top tamarins (Saguinus oedipus), a cooperatively breeding New World primate. In experiment 1 we show that individuals give significantly more food to a trained conspecific who unilaterally gives food than to a conspecific who unilaterally never gives food. The apparent contingency of the tamarins' food-giving behaviour motivated the design of experiments 2-4. Results from all three experiments show that altruistic food giving is mediated by prior acts of altruistic food giving by a conspecific. Specifically, tamarins do not give food to unrelated others when the food received in the past represents the by-product of another's selfish actions (experiments 2 and 3) or when a human experimenter gives them food (experiment 4) as did the unilateral altruist in experiment 1. By contrast, if one tamarin gives another food without obtaining any immediate benefit, then the recipient is more likely to give food in return. Overall, results show that tamarins altruistically give food to genetically unrelated conspecifics, discriminate between altruistic and selfish actions, and give more food to those who give food back. Tamarins therefore have the psychological capacity for reciprocally mediated altruism.
在自然界中，基因不相关的个体之间进行利他性食物给予的情况很少见。现有的少数例子表明，当动物给与非亲属其他个体食物时，它们可能是基于互利或互惠利他关系才这样做的。我们展示了四项实验的结果，这些实验旨在梳理出在基因不相关的棉顶狨（Saguinus oedipus）之间介导食物给予行为的因素，棉顶狨是一种进行合作繁殖的新大陆灵长类动物。在实验1中，我们发现，与单方面从不给予食物的同种个体相比，个体显著更愿意给与经过训练、单方面给予食物的同种个体更多食物。狨猴食物给予行为的这种明显的偶然性促使了实验2 - 4的设计。所有这三项实验的结果都表明，利他性食物给予是由同种个体先前的利他性食物给予行为介导的。具体来说，当过去获得的食物代表另一个体自私行为的副产品时（实验2和3），或者当人类实验者像实验1中的单方面利他者那样给它们食物时（实验4），狨猴不会给与非亲属其他个体食物。相比之下，如果一只狨猴给另一只狨猴食物而没有获得任何直接利益，那么接受者更有可能回报以食物。总体而言，结果表明，狨猴会利他性地给与基因不相关的同种个体食物，区分利他行为和自私行为，并且会给那些回报食物的个体更多食物。因此，狨猴具有互惠介导利他行为的心理能力。
