Department of Life Sciences, School of Life and Environmental Sciences, College of Health and Science, University of Lincoln, Lincoln, UK.
School of Psychology, College of Health and Science, University of Lincoln, Lincoln, UK.
Am J Primatol. 2024 Sep;86(9):e23664. doi: 10.1002/ajp.23664. Epub 2024 Jul 21.
Changes in the rate of self-directed behavior-a proxy for social tension-offer valuable insights into individuals' experiences of social interactions. Many studies have tested the tension-reduction hypothesis, whereby grooming is expected to reduce social tension in the grooming partners. However, it is still unclear whether responses to grooming are affected by social factors such as an individual's role or social relationship with their partner, and whether responses are similar for females and males. Focussing on same-sex grooming in Yakushima Japanese macaques (Macaca fuscata yakui), we analyzed the effects of two social factors on the change in the rate of self-scratching after receiving grooming: sitting in contact with their partner outside of grooming contexts (as a measure of relationship strength) and rank distance. We collected 10-min postgrooming and matched-control focal samples on recipients of grooming. After controlling for postinhibitory rebound effects, grooming reduced scratching in females (suggesting that grooming was relaxing for the receiver), but not in males. In females, this reduction was associated with increased sitting in contact and increased rank distance: being groomed was more tension-reducing if the grooming partners spent time together outside of grooming contexts, or if their difference in rank was greater and therefore more conspicuous. The reduction effect was mediated by sitting in contact only when females had a higher-ranking-that is, more dominant and potentially aggressive-groomer. Our findings suggest that not all grooming interactions are perceived as equal, which has implications for its use as an index of relationship quality. To our knowledge, this represents the first study of postgrooming social tension in male Japanese macaques and our results highlight the need for caution when generalizing findings from only one sex to the species level.
自我导向行为率的变化——一种社交紧张的代理指标——为我们提供了有价值的线索，以了解个体在社交互动中的体验。许多研究都检验了紧张缓解假说，该假说认为梳理行为可以降低梳理伙伴的社交紧张感。然而，目前尚不清楚个体在梳理后的反应是否受到社交因素的影响，例如个体的角色或与伴侣的社交关系，以及雌性和雄性的反应是否相似。我们专注于屋久岛日本猕猴（Macaca fuscata yakui）的同性梳理行为，分析了两个社会因素对接受梳理后自我抓挠率变化的影响：梳理时与伴侣坐在接触状态下（作为关系强度的衡量标准）和等级距离。我们对接受梳理的猕猴收集了梳理后 10 分钟的焦点样本和匹配的对照样本。在控制了后抑制反弹效应后，梳理减少了雌性猕猴的抓挠行为（表明梳理对接收者有放松作用），但对雄性猕猴没有影响。在雌性猕猴中，这种减少与增加的接触坐立时间和增加的等级距离有关：如果梳理伙伴在梳理环境之外有更多的共处时间，或者它们之间的等级差异更大且更明显，那么梳理对减少紧张的效果就越大。这种减少效应仅在雌性猕猴有一个高等级的梳理者时才通过接触坐立来介导，也就是说，梳理者具有更高的等级，更具支配力和潜在的攻击性。我们的研究结果表明，并非所有的梳理互动都被视为平等的，这对将其作为关系质量的指标的使用有影响。据我们所知，这是第一项对雄性日本猕猴梳理后社交紧张的研究，我们的研究结果强调了在将仅从一个性别获得的发现推广到物种水平时需要谨慎。
