Cognitive Psychology Unit, Institute of Psychology, The Faculty of Social and Behavioral Sciences, Leiden University, Wassenaarseweg 52, 2333 AK, Leiden, The Netherlands.
Apenheul Primate Park, J.CWilslaan 21, 7313 HK, Apeldoorn, The Netherlands.
Sci Rep. 2024 May 27;14(1):12095. doi: 10.1038/s41598-024-62187-9.
Primate faces provide information about a range of variant and invariant traits, including some that are relevant for mate choice. For example, faces of males may convey information about their health or genetic quality through symmetry or facial masculinity. Because perceiving and processing such information may have bearing on the reproductive success of an individual, cognitive systems are expected to be sensitive to facial cues of mate quality. However, few studies have investigated this topic in non-human primate species. Orang-utans are an interesting species to test mate-relevant cognitive biases, because they are characterised by male bimaturism: some adult males are fully developed and bear conspicuous flanges on the side of their face, while other males look relatively similar to females. Here, we describe two non-invasive computerised experiments with Bornean orang-utans (Pongo pygmaeus), testing (i) immediate attention towards large flanges and symmetrical faces using a dot-probe task (N = 3 individuals; 2F) and (ii) choice bias for pictures of flanged males over unflanged males using a preference test (N = 6 individuals; 4F). In contrast with our expectations, we found no immediate attentional bias towards either large flanges or symmetrical faces. In addition, individuals did not show a choice bias for stimuli of flanged males. We did find exploratory evidence for a colour bias and energy efficiency trade-offs in the preference task. We discuss our null results and exploratory results in the context of the evolutionary history of Bornean orang-utans, and provide suggestions for a more biocentric approach to the study of orang-utan cognition.
灵长类动物的面部提供了一系列可变性和不变性特征的信息，包括一些与配偶选择相关的特征。例如，雄性的面部可能通过对称性或面部男性特征传达关于其健康或遗传质量的信息。因为感知和处理这些信息可能会影响个体的生殖成功，所以认知系统应该对伴侣质量的面部线索敏感。然而，很少有研究在非人类灵长类物种中调查这个话题。猩猩是测试与配偶相关的认知偏见的有趣物种，因为它们具有雄性双态性的特征：一些成年雄性完全发育，面部两侧有明显的凸缘，而其他雄性则看起来与雌性相似。在这里，我们描述了两项针对婆罗洲猩猩（Pongo pygmaeus）的非侵入性计算机实验，测试了（i）使用点探测任务对大凸缘和对称面部的即时注意力（N=3 个个体；2F），以及（ii）使用偏好测试对有凸缘雄性的图片的选择偏好（N=6 个个体；4F）。与我们的预期相反，我们没有发现对大凸缘或对称面部的即时注意力偏向。此外，个体对无凸缘雄性的刺激没有表现出选择偏好。我们确实在偏好任务中发现了颜色偏好和能量效率权衡的探索性证据。我们在婆罗洲猩猩进化历史的背景下讨论了我们的零结果和探索性结果，并为更以生物为中心的猩猩认知研究提供了建议。
