New research finds that smiles can be used to both soothe¹ or attack - at least, as far as the brain's stress pathways are concerned.

新研究发现，微笑既可用于安抚，也能产生伤害，至少对于大脑的应激通路确是如此。

The study, published by researchers from the University of Wisconsin-Madison and Bar-Ilan University, looked at the interaction between nonverbal feedback and the activity of the hypothalamic-pituitary-adrenal axis², our body's central stress response system.

威斯康星大学麦迪逊大学和巴伊兰大学的研究人员发表的这项研究，对非语言反馈与下丘脑-垂体-肾上腺轴，即我们身体的主要压力应对系统之间的互动进行了调查。

The authors report that individuals with higher heart-rate variability showed the widest range of responses to different smiles.

作者报告称，心率可变性大的人对不同笑容的反应差异性也更大。

Higher heart rate variability has previously³ been correlated with a higher ability to recognize facial expressions.

此前，心率可变性大就被认为与辨认面部表情的能力更强有关。

"The findings provide further evidence for the view that smiles do not necessarily constitute positive nonverbal feedback, and that they may impact social interactions by affecting the physiological⁴ reaction of people who perceive them," the authors write.

作者们写道：“研究结果进一步为以下观点提供证据，即微笑并不一定就是正面的非语言反馈。通过影响了解其含义的人的身体反应，微笑有可能对社交互动模式产生影响。”

"In addition, cortisol appears to support the detection of social threat and coordinate⁵ biological activity needed to adequately respond to the threat."

“此外，皮质醇似乎能够支持对社交威胁的检测，并协调需要被用于应付威胁的生物学活动。”

The findings help patch in our understanding of the depth of nonverbal communication in human language -- as a tool to unnerve, a hand to soothe, and as an outside effect on our psychological state.

这项研究增加了我们对人类之间的非语言沟通的理解深度，非语言沟通能够作为使人焦虑和给人安慰的手段，也是对我们心理状态产生作用的外部因素。

However, the team cautions that because of the small sample of exclusively male participants, the findings shouldn't be generalized until replicated⁶.

但是，该团队提醒道，因为该研究的样本较小，而且只有男性受测者，所以这项发现在被复现之前不能推广到所有人群。

Thus, further research will need to explore whether or not men and women react differently to the same kind of smile, and to test more overt⁷ (both negative and positive) facial expressions.

因此，还需要进一步的研究来探究男性和女性对相同种类微笑的反应是否相关，并测试更多种类（消极与积极的）的面部表情。