Beauty sleep is a real thing, according to researchers who have shown that people who miss out on sleep do appear less attractive to others.

“美容觉”确有其事。研究人员表示，比起睡得好的人，睡眠不足的人显得没有那么光彩照人。

A couple of bad nights is enough to make a person look "significantly" more ugly, their sleep experiments suggest.

研究人员开展的睡眠实验结果显示，几个晚上睡得不好便足以让一个人看起来“特别地”不好看。

Dark-circled "panda" eyes and puffy lids can even put others off socialising with you, they say.

研究人员称，黑眼圈和肿肿的眼皮甚至可能会让身边的人远离你。

People were rated by strangers as less healthy and approachable when they had tired faces.

当人们表现出疲惫相时，素不相识的人会认为他们的身体状况不佳且不是很好接近。

The researchers asked 25 university students, some male and some female, to be the guinea pigs in their sleep experiment.

研究人员请25名大学生参与了睡眠实验，其中有男有女。

The volunteers - who were given payment for their help - were sent home with a kit¹ that would measure their night-time movements to check that they had not cheated and slept when they should not have.

志愿者在参与实验后可以得到一定的报酬。研究人员向他们各自发放了一套工具，让他们带回家。这套工具会通过测量他们夜间的活动，以验证他们没有说谎，在原本不会睡觉的时候进入睡眠状态。

They were asked to get a good night's sleep for two consecutive² nights.

志愿者被要求连续两个晚上保持良好的睡眠状态。

A week later, they were asked to restrict themselves to only four hours sleep per night for two nights in a row.

一个星期后，他们被要求将他们的睡眠时间压缩到连续两天每天仅睡四个小时。

The researchers took make-up free photos of the volunteers after both the good and the bad sleep sessions.

在志愿者进行了好的睡眠和差的睡眠之后，研究人员分别拍摄了志愿者们的素颜照片。

Next, they asked 122 strangers - women and men living in Sweden's capital city, Stockholm - to have a look at the photos and rate them on attractiveness, health, sleepiness and trustworthiness, as well as asking them: "How much would you like to socialise with this person in the picture?"

接着，研究人员召集了122名与志愿者素不相识的陌生人。他们当中有男有女，都住在瑞典首都斯德哥尔摩。这些人被要求看着志愿者的照片，对他们的魅力程度、健康状况、睡眠情况和信任程度进行评价。研究人员还会问他们一个问题：“你有多想跟照片上的这个人交朋友？”

The strangers were good at judging if the person they were looking at was tired, and, if they were sleepy, their attractiveness score suffered.

这群人的眼力很好。如果照片上的人显得疲倦不堪，或者看起来很缺觉，他们魅力程度的分数便很低。

The strangers also said they would be less willing to socialise with the tired students, who they also perceived to be less healthy, Royal Society Open Science journal reports.

据英国期刊《皇家协会开放科学》报道，这些陌生人也表示，他们更不愿意与那些看起来很累的学生交朋友，他们认为这些人的身体状况不太好。

The Karolinska Institute researchers says this makes sense in evolutionary³ terms.

来自卡罗林斯卡学院的研究人员说，从进化的角度来看，这十分符合常理。

"An unhealthy-looking face, whether due to sleep deprivation⁴ or otherwise, might activate⁵ disease-avoiding mechanisms⁶ in others."

“一张看起来不健康的脸，不管它是由于睡眠不足还是其他原因导致的，都可能会激活其他人身体内躲避疾病的机制。”

In other words, people don't want to hang around with people who might be ill, whereas someone who looks energetic and fit will hold lots of appeal.

换句话说，人们不想跟可能患病的人待在一起。而那些看起来活力四射、身体健康的人则魅力十足。

Lead researcher Dr Tina Sundelin added: "I don't want to worry people or make them lose sleep over these findings though.

首席研究员蒂娜•孙德琳博士补充道：“我不希望这些实验结果让人们担忧或者睡得不好。”

"Most people can cope just fine if they miss out on a bit of sleep now and again."

“偶尔睡得不好没有关系，大部分人都可以恢复得很好。”

Dr Gayle Brewer⁷, a psychology⁸ expert at the University of Liverpool and member of the British Psychological Association, said: "Judgement of attractiveness is often unconscious, but we all do it, and we are able to pick up on even small cues like whether someone looks tired or unhealthy.

盖利•布鲁尔博士是利物浦大学的一名心理学专家及英国心理学协会成员。他说：“对外表魅力程度的评价往往是无意识的，但是我们一直都在做这件事。我们能够从一些很小的细节，比如说这个人是否疲惫或者是否健康，来对他人进行评价。”

"We want our partners to be attractive and energetic.

“我们希望我们的伴侣看起来魅力十足，充满活力。”

"This study is a good reminder⁹ of how important sleep is to us."

“这个研究对我们来说是一个很好的提醒，它告诉我们，睡眠是多么重要。”