While it has been demonstrated that even subtle variation in human facial expressions can lead to significant changes in the meaning and function of expressions, relatively few studies have examined primate facial expressions using similarly objective and rigorous analysis. Construction of primate facial expression repertoires may, therefore, be oversimplified, with expressions often arbitrarily pooled and/or split into subjective pigeonholes. Our objective is to assess whether subtle variation in primate facial expressions is linked to variation in function, and hence to inform future attempts to quantify complexity of facial communication.

中文翻译：

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沉默的裸露牙齿展示的形态变异在冠猕猴（Macaca nigra）中具有不同的社交互动结果。

尽管已经证明即使人类面部表情的细微变化也可能导致表情含义和功能的重大变化，但相对较少的研究使用相似的客观和严格的分析方法来检查灵长类动物面部表情。因此，灵长类面部表情库的构建可能会被过度简化，而表情通常会被任意合并和/或分割为主观信鸽。我们的目标是评估灵长类动物面部表情的细微变化是否与功能变化有关，从而为将来量化面部表情交流的复杂性提供依据。