ESM raw data from Goats prefer positive human emotional facial expressions

Domestication has shaped the physiology and the behaviour of animals to better adapt to human environments. Therefore, human facial expressions may be highly informative for animals domesticated for working closely with people, such as dogs and horses. However, it is not known whether other animals, and particularly those domesticated primarily for production, such as goats, are capable of perceiving human emotional cues. In this study, we investigated whether goats can distinguish human facial expressions when simultaneously shown two images of an unfamiliar human with different emotional valences (positive/happy or negative/angry). Both images were vertically attached to a wall on one side of a test arena, 1.3 m apart, and goats were released from the opposite side of the arena (distance of 4.0 m) and were free to explore and interact with the stimuli during the trials. Each of four test trials lasted 30 s. Overall, we found that goats preferred to interact first with happy faces, meaning that they are sensitive to human facial emotional cues. Goats interacted first, more often and for longer duration with positive faces when they were positioned on the right side. However, no preference was found when the positive faces were placed on the left side. We show that animals domesticated for production can discriminate human facial expressions with different emotional valences and prefer to interact with positive ones. Therefore, the impact of domestication on animal cognitive abilities may be more far-reaching than previously assumed.

驯化作用塑造了动物的生理与行为特征，使其更适配人类生存环境。因此，对于那些为与人类密切协作而被驯化的动物（如犬类与马属动物）而言，人类面部表情往往能传递大量信息。但目前尚不明确，其他动物——尤其是那些主要以生产为目的被驯化的动物（如山羊）——是否能够识别人类的情绪线索。本研究旨在探究：当山羊同时被展示两张情绪效价不同的陌生人类面部图像（正性/愉悦或负性/愤怒）时，是否能够区分二者。两张图像均垂直张贴于实验区域一侧的墙面上，二者间距为1.3米；山羊从实验区域的对侧（与墙面相距4.0米）被释放，并可在实验过程中自由探索并与刺激物互动。每组四次测试试次均持续30秒。整体而言，山羊更倾向于先与愉悦的面部图像互动，这表明它们能够感知人类面部的情绪线索。当正性情绪面部图像位于右侧时，山羊会优先、更频繁且更持久地与正性面孔互动。但当正性情绪面部图像位于左侧时，山羊未表现出此类偏好。本研究证实：以生产为目的驯化的动物，能够区分不同情绪效价的人类面部表情，并更偏好与正性情绪面孔互动。因此，驯化对动物认知能力的影响，或许比此前研究所认为的更为深远。