Data from: Functionally relevant responses to human facial expressions of emotion in the domestic horse (Equus caballus)

Whether non-human animals can recognize human signals, including emotions, has both scientific and applied importance, and is particularly relevant for domesticated species. This study presents the first evidence of horses' abilities to spontaneously discriminate between positive (happy) and negative (angry) human facial expressions in photographs. Our results showed that the angry faces induced responses indicative of a functional understanding of the stimuli: horses displayed a left-gaze bias (a lateralization generally associated with stimuli perceived as negative) and a quicker increase in heart rate (HR) towards these photographs. Such lateralized responses towards human emotion have previously only been documented in dogs, and effects of facial expressions on HR have not been shown in any heterospecific studies. Alongside the insights that these findings provide into interspecific communication, they raise interesting questions about the generality and adaptiveness of emotional expression and perception across species.非人类动物能否识别人类的各类信号（包括情绪信号），兼具科学与应用价值，对于家养物种而言尤为相关。本研究首次提供证据表明，马匹能够自发辨别照片中人类的积极（愉悦）与消极（愤怒）面部表情。我们的研究结果显示，愤怒面孔会诱发表明马匹对刺激具备功能性理解的反应：当面对这类照片时，马匹表现出左侧注视偏侧化（该偏侧化现象通常与被感知为消极的刺激相关），且心率（Heart Rate, HR）上升更快。此前，这类针对人类情绪的偏侧化反应仅在犬类中被记录到，而面部表情对心率的影响尚未在任何跨物种研究中得到证实。除了这些发现为跨物种交流提供的洞见之外，它们还引出了有趣的问题：情绪表达与感知在不同物种间的普遍性与适应性究竟如何。