Centre for Comparative and Evolutionary Psychology, Department of Psychology, University of Portsmouth , UK.
Centre for Comparative and Evolutionary Psychology, Department of Psychology, University of Portsmouth , UK ; Perception, Action and Cognition Research Group, School of Psychology, University of Lincoln , UK.
PeerJ. 2015 Mar 19;3:e827. doi: 10.7717/peerj.827. eCollection 2015.
Primate facial expressions are widely accepted as underpinned by reflexive emotional processes and not under voluntary control. In contrast, other modes of primate communication, especially gestures, are widely accepted as underpinned by intentional, goal-driven cognitive processes. One reason for this distinction is that production of primate gestures is often sensitive to the attentional state of the recipient, a phenomenon used as one of the key behavioural criteria for identifying intentionality in signal production. The reasoning is that modifying/producing a signal when a potential recipient is looking could demonstrate that the sender intends to communicate with them. Here, we show that the production of a primate facial expression can also be sensitive to the attention of the play partner. Using the orangutan (Pongo pygmaeus) Facial Action Coding System (OrangFACS), we demonstrate that facial movements are more intense and more complex when recipient attention is directed towards the sender. Therefore, production of the playface is not an automated response to play (or simply a play behaviour itself) and is instead produced flexibly depending on the context. If sensitivity to attentional stance is a good indicator of intentionality, we must also conclude that the orangutan playface is intentionally produced. However, a number of alternative, lower level interpretations for flexible production of signals in response to the attention of another are discussed. As intentionality is a key feature of human language, claims of intentional communication in related primate species are powerful drivers in language evolution debates, and thus caution in identifying intentionality is important.
灵长类动物的面部表情被广泛认为是由反射性情绪过程支撑的，而不受自愿控制。相比之下，其他灵长类动物的交流方式，尤其是手势，被广泛认为是由有意的、有目的的认知过程支撑的。造成这种区别的一个原因是，灵长类动物手势的产生通常对接收者的注意力状态敏感，这种现象被用作识别信号产生意图的关键行为标准之一。其推理是，当潜在接收者在看时，修改/产生信号可以证明发送者有意与他们交流。在这里，我们表明灵长类动物面部表情的产生也可以对玩伴的注意力敏感。使用猩猩（Pongo pygmaeus）面部动作编码系统（OrangFACS），我们证明了当接收者的注意力指向发送者时，面部运动更加剧烈和复杂。因此，表演脸的产生不是对游戏的自动反应（或者只是游戏行为本身），而是根据上下文灵活产生的。如果对注意力姿态的敏感性是意图的一个很好的指标，那么我们也必须得出结论，猩猩的表演脸是有意产生的。然而，我们讨论了一些替代的、更低层次的解释，用于灵活地产生对另一个信号的注意力的反应。由于意图是人类语言的一个关键特征，因此在相关灵长类物种中有意沟通的主张是语言进化辩论的有力驱动因素，因此谨慎识别意图很重要。
