大型類人猿の向社会的行動におよぼす性・神経ホルモンの影響に関する比較認知科学研究

我们在第一年测试了猩猩的亲社会性和互惠性。第二年的计划是比较猩猩和黑猩猩的亲社会倾向，并检查荷尔蒙对其影响。我们确实分析了黑猩猩和猩猩的基础雌激素、孕激素和催产素水平，以进一步检验激素对亲社会倾向的影响。然而，由于实验环境的实际原因，我们不能对黑猩猩进行鼻内注射催产素，因此我们只对圈养黑猩猩进行了亲社会和互惠的行为实验。本研究旨在检验黑猩猩的亲社会选择是否受到不同的报酬分配(平等/有利/不利)和人类伴侣的不公平行为(亲社会/自私)的影响。与其他不公平的任务不同，我们使用了亲社会选择实验，让黑猩猩在对待伴侣时扮演亲社会或自私的积极角色。我们的结果表明，当黑猩猩自己拒绝完成任务时，他们自己得到的回报比他们的伴侣更不喜欢时，他们会表现出厌恶的反应。然而，这种行为倾向并没有导致黑猩猩做出自私的选择。综合第一年的结果，我们的结果表明，在选择范式实验中，黑猩猩和猩猩在自愿与他人分享利益的方式上没有差异，对不平等的厌恶可能在两个物种中表现出不同的形式，这是调节互惠所必需的。

We tested orangutan prosociality and reciprocity in the first year. The plan for the second year was to compare orangutans to chimpanzees on their prosocial tendency and to examine the hormonal influence on it. We did analyse baseline estrogen, progesterone, and oxytocin levels from chimpanzees and orangutans to further examine the effect of hormones on prosocial propensity. However, due to some practical reasons of the experimental setting, we could not conduct the intranasal oxytocin administration to the chimpanzees, and therefore we only conducted behavioral experiments on prosociality and reciprocity in captive chimpanzees.The current study was designed to test whether chimpanzees’ prosocial choices are influenced by differential reward distributions (equal/advantageous/disadvantageous) and also by unfair behaviors (prosocial/selfish) of human partners. Unlike other inequity tasks, we used a prosocial choice experiment to give the chimpanzees an active role to be prosocial or selfish toward their partner. Our results show that the chimpanzees show aversive reactions when they themselves had a less preferred reward than their partners by rejecting to do the task. However, this behavioral tendency did not lead chimpanzee’s to make selfish choices.Taken together with the results of 1st year, our results suggest that there is no difference between chimpanzees and orangutans in a way of voluntarily sharing benefits with others in a choice paradigm experiment and that aversion to inequity, necessary for regulating reciprocity, may take different forms in both species.