Evers Ellen, de Vries Han, Spruijt Berry M, Sterck Elisabeth H M
Department of Animal Ecology, Utrecht University , Utrecht , The Netherlands.
Department of Animal Ecology, Utrecht University, Utrecht, The Netherlands; Animal Science Department, Biomedical Primate Research Center, Rijswijk, The Netherlands.
PeerJ. 2016 Jan 5;4:e1488. doi: 10.7717/peerj.1488. eCollection 2016.
Whether and how primates are able to maintain long-term affiliative relationships is still under debate. Emotional bookkeeping (EB), the partner-specific accumulation of emotional responses to earlier interactions, is a candidate mechanism that does not require high cognitive abilities. EB is difficult to study in real animals, due to the complexity of primate social life. Therefore, we developed an agent-based model based on macaque behavior, the EMO-model, that implements arousal and two emotional dimensions, anxiety-FEAR and satisfaction-LIKE, which regulate social behavior. To implement EB, model individuals assign dynamic LIKE attitudes towards their group members, integrating partner-specific emotional responses to earlier received grooming episodes. Two key parameters in the model were varied to explore their effects on long-term affiliative relationships: (1) the timeframe over which earlier affiliation is accumulated into the LIKE attitudes; and (2) the degree of partner selectivity. EB over short and long timeframes gave rise to low variation in LIKE attitudes, and grooming partner preferences were only maintained over one to two months. Only EB over intermediate-term timeframes resulted in enough variation in LIKE attitudes, which, in combination with high partner selectivity, enables individuals to differentiate between regular and incidental grooming partners. These specific settings resulted in a strong feedback between differentiated LIKE attitudes and the distribution of grooming, giving rise to strongly reciprocated partner preferences that could be maintained for longer periods, occasionally up to one or two years. Moreover, at these settings the individual's internal, socio-emotional memory of earlier affiliative episodes (LIKE attitudes) corresponded best to observable behavior (grooming partner preferences). In sum, our model suggests that intermediate-term LIKE dynamics and high partner selectivity seem most plausible for primates relying on emotional bookkeeping to maintain their social bonds.
灵长类动物是否以及如何能够维持长期的亲和关系仍存在争议。情感记账（EB），即对早期互动的特定伙伴情感反应积累，是一种不需要高认知能力的潜在机制。由于灵长类动物社会生活的复杂性，在真实动物中研究EB很困难。因此，我们基于猕猴行为开发了一个基于主体的模型，即EMO模型，该模型实现了唤醒以及调节社会行为的两个情感维度，焦虑-恐惧和满足-喜欢。为了实现EB，模型个体对其群体成员分配动态的喜欢态度，整合对早期接受的梳理事件的特定伙伴情感反应。模型中的两个关键参数被改变以探索它们对长期亲和关系的影响：（1）早期亲和积累到喜欢态度中的时间范围；（2）伙伴选择性的程度。短期和长期时间范围内的EB导致喜欢态度的变化较小，梳理伙伴偏好仅在一到两个月内得以维持。只有中期时间范围内的EB导致喜欢态度有足够的变化，再结合高伙伴选择性，使个体能够区分常规和偶然的梳理伙伴。这些特定设置导致在差异化的喜欢态度和梳理分布之间产生强烈的反馈，从而产生能够长期维持的强烈互惠伙伴偏好，偶尔可达一两年。此外，在这些设置下，个体对早期亲和事件（喜欢态度）的内部社会情感记忆与可观察到的行为（梳理伙伴偏好）最为相符。总之，我们的模型表明，对于依靠情感记账来维持社会纽带的灵长类动物来说，中期的喜欢动态和高伙伴选择性似乎最为合理。
