Evidence from humans suggests that the expression of emotions can regulate social interactions and promote coordination within a group. Despite its evolutionary importance, social communication of emotions in non-human animals is still not well understood. Here, we combine behavioural and physiological measures, to determine if animals can distinguish between vocalisations linked to different emotional valences (positive and negative). Using a playback paradigm, goats were habituated to listen to a conspecific call associated with positive or negative valence (habituation phase) and were subsequently exposed to a variant of the same call type (contact call) associated with the opposite valence (dishabituation phase), followed by a final call randomly selected from the habituation phase as control (rehabituation phase). The effects of the calls on the occurrence of looking and cardiac responses in these phases were recorded and compared. We found that when the valence of the call variant changed, goats were more likely to look at the source of the sound, indicating that they could distinguish calls based on their valence. Heart rate was not affected by the valence of the calls played, whereas heart-rate variability tended to be higher in the habituation and rehabituation phases, when positive calls were played compared to negative ones. Together, the behavioural and physiological measures provide evidence suggesting, first, that goats are able to distinguish call variants based on their valence, and second, that goat behaviour and cardiac responses are affected by call valence. This study indicates that auditory modalities are a potent means to communicate emotions in non-human animals. These findings can contribute to our understanding of the evolution of emotion perception in non-human animals.

中文翻译：

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山羊区分与情绪相关的积极和消极的发声


来自人类的证据表明，情绪的表达可以调节社会互动并促进群体内的协调。尽管它在进化上很重要，但非人类动物的情感社会交流仍然没有得到很好的理解。在这里，我们结合了行为和生理测量，以确定动物是否能够区分与不同情绪效价（积极和消极）相关的发声。使用回放范例，山羊习惯于聆听与正价或负价相关的同种叫声（习惯阶段），随后暴露于与相反价相关的相同叫声类型（接触叫声）的变体（去习惯阶段），接下来是从习惯阶段随机选择的最终呼叫作为对照（恢复阶段）。记录并比较了这些阶段中呼叫对观看和心脏反应发生的影响。我们发现，当叫声变体的价发生变化时，山羊更有可能看声音的来源，这表明它们可以根据叫声的价来区分叫声。心率不受所播放呼叫效价的影响，而在习惯化和恢复阶段，当播放积极呼叫时，与消极呼叫相比，心率变异性往往更高。总之，行为和生理测量提供的证据表明，首先，山羊能够根据其效价区分叫声变体，其次，山羊的行为和心脏反应受到叫声效价的影响。这项研究表明，听觉方式是非人类动物交流情感的有效手段。 这些发现有助于我们理解非人类动物情绪感知的进化。