2013 Fiscal Year Annual Research Report
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
| Project/Area Number |
13J00666
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| Research Institution | Kyoto University |
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Principal Investigator |
キム イェナ 京都大学, 霊長類研究所, 特別研究員(DC2)
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| Keywords | Choice paradigm / Orangutans / Prosociality / Recirocity / Sociality / Unfairness |
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| Research Abstract |
The purpose of the research was to uncover the origin of prosocial and cooperative behavior by comparing primates having different socialsystems. The plan for the first year was comparing orangutans to chimpanzees on their prosocial tendency. We did run two experiments on orangutan prosociality and reciprocity, but could not conduct a same experiment with chimpanzees due to the incompatibility of experimental apparatus. We did analyze fecal estradiol and progesterone levels of female orangutans to see the effect of female estrous cycle on male's prosocial tendency, but one female was pregnant during the experimental period and another fernale had a problem on her ovulatory cycles. Therefore, we could not test the hormonal influence on prosociality. Here are the summaries of the two experiments.
Study 1 : Humans are thought to be unique in their ability to voluntarily help others even though it may sometimes incur substantial costs. However, there are a growing number of studies showing
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that prosocial behaviors can be observed, not only in humans, but also among nonhuman primates that live in complex social gmups. Prosociality has often been described as a major factor that facilitates group living. Nonetheless, it has seldom been explored whether solitary living primates, such as orangutans, share this propensity or not. In the presont study, we tested four captive orangutans (Pongo abelii X pigmaeus, Pongo pigmaeus) in a simple food-dellvering task where they had a choice, incurring the same cost, between getting a food reward for themselves and providing a food reward to a conspecific recipient passively sitting in an adjacent booth, in addittion to their own reward. Two oranngutans played the actor's role, and all four orangutans participated as recipients. The results showed that the actors did not choose to deliver food to the recipients more often than expected by chance (51.3% on average). The control condition demonstrated that this tendency was independent of the actor's understanding of the task. These findings suggest that orangutans do not spontaneously share benefits with other conspecifics, even when the prosocial choice does not disadvantage them. This study is consistent with previous findings hypothesizing that the enhanced prosocial propensity shown in humans and other group living primates is an evolutionary outcome of living in complex social environments.
Study 2 : One critical point for understanding the evolution of reciprocity is a psychological mechanism to detect a free-rider. Among them, sensitivity to unfaimess has been widely tested in group living primates. EXperimental studios of chimpanzee and capuchin sensitivity to unfaimess show that they display aversive reactions when the partner has a better reward than themselves. Even though there have been few studies testing orangutan sensitivity to unfaimess outcomes, no study has yet tested whether orangutans are sensitive to a partner's unfair intentions. We tested two captive orangutans, living in a social group, with human participants who were randomly assigned either to be prosocial or selfish, using the same protocol of proviouse xperiments on orangutan prosociality. Our results showed that ncither prosocial choices nor selfish choices by human patners affected the prosocial choices orangutans made afterwards. These findings suggest that species' sociality plays a more critical role than the current soeial environment in embedded psychological mechanisms, which is important for regulating reciprocity. Less
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Due to the incompatibility of the experimental apparatus, used for orangutan prosocial experiment, with chimpanzee experiment, we had to modify our experimental design and schedules. Therefore, we decided to conduct a further experiment on reciprocity in orangutans instead of chimpanzee prosociality. Chimpanzee prosociality experiment will be replaced to a simple food sharing task.
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| Strategy for Future Research Activity |
We will conduct an experiment on food sharing, another type of prosocial behaviors frequently observed in the wild, both for captive chimpanzees and orangutans with intranasal oxytocin administration to see the effect of administered oxytocin on food sharing behavior. Furthehrnore, we will conduct a computerized matching to sample experiment with baby face stimuli and analyze urinary oxytocin levels from the subjects after being exposed to the visual stimuli, to see the effect of visual perception of baby faces on peripheral oxytocin release. These bidirectional stUdy design will provide an opportunity to better understand the role of oxytocin on prosociality.
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Research Products
(5 results)
