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关于睡眠你所不知道的惊人理论

更新时间:2019/10/22 9:58:29 来源:纽约时报中文网 作者:佚名

The surprising truth about why we sleep and how much we need
关于睡眠你所不知道的惊人理论

They say that an elephant never forgets. It is also often stated that one of the functions of sleep is to consolidate memories. If both of those things were true, then you'd expect elephants to sleep a lot – but the truth is, the massive pachyderms, which have the biggest brains of any land mammal, sleep just two hours each night.

有人说大象永远不会忘事。还有人说睡眠的作用之一在于强化巩固记忆。如果上述两种说法都对的话,就能推导得出"大象睡眠时间很长"的结论,但是实际上,这种无论体型还是脑体积都在陆地哺乳动物中排名第一的动物每晚却只睡两个小时。

Even though we sleep almost every night of our lives, it is also one of the most commonly misunderstood aspects of behaviour. It turns out that a lot of common ideas about sleep, much like the example above, are simply incorrect.

在我们的生命中,我们几乎每晚都在睡眠中度过,但是睡眠却是最受误解的一种人类行为。很多关于睡眠的看法,就如上面的例子一样,是完全错误的。

Have you heard, for example, that thanks to electric lighting and the faint glow emanating from the smartphone screens we stare at before going to bed, we get fewer hours of shut-eye than our hunter-gatherer ancestors?

例如,你是否听说过这种说法:由于现代电气照明,以及我们在睡觉前观看智能手机屏幕时发出的微光,现代人的睡眠时间要短于我们打猎采摘的祖先?

"Many people have heard this so many times through the media that they believe it," says Jerry Siegel, director of the University of California Los Angeles Center for Sleep Research. He admits it’s a compelling story, even though it is – probably – completely untrue. "The trouble is we don't really have any data on this," he says. "The devices that we use to measure sleep weren't invented until long after the invention of electric light."

"许多人在各路媒体上都看到过类似信息,他们也对此深信不疑,"加州大学洛杉矶分校睡眠研究中心主任杰里·西格尔(Jerry Siegel)表示。他承认,这些文章很能震撼人心,哪怕它们有可能根本站不住脚。"问题在于,我们在这方面没有积累任何数据,"他说。"睡眠质量测量仪的发明时间比电灯要晚好多年。"

Since it's impossible to figure out how much time our ancestors spent sleeping, Siegel decided to do the next best thing. He travelled to Tanzania, Namibia, and Bolivia, spending time with contemporary hunter-gatherer groups. These people are born into an environment that is as close as can be found today to the one our ancestors would have lived in.

要想知道我们祖先每天的睡眠时间有多长是不可能的,因此西格尔决定另想办法。他跑到坦桑尼亚、纳米比亚和玻利维亚这些国家去考察当地的狩猎/采摘部落。这些部落居民生活在目前能够找到的和我们祖先十分类似的环境中。

For their entire lives, these hunter-gatherer societies have lived – and slept - without any of the modern devices we suspect disturb our own rest. Several thousand miles separate the two groups in Africa, while the third is descended from a group that migrated out of Africa, travelled through Asia, crossed the Alaskan land bridge before then moving through North America and into South America. Despite this remarkable divergence, all three groups sleep about the same amount of time each night: six-and-a-half hours, on average. According to Siegel, there's no reason to believe our ancestors would have slept any more than that.

这些狩猎/采摘部落居民在终其一生中都不会见到会打扰我们休息的现代化装置。其中两个部落位于非洲,相距数千公里之遥,第三个部落则是最早从非洲迁出,然后穿越亚洲大陆,跨越阿拉斯加大陆桥,通过北美最终抵达南美。尽管这三个部落彼此间相距遥远,但是它们的居民每晚睡眠时间却十分接近:平均6.5小时。西格尔表示,没有理由认为我们的祖先当初的睡眠时间会超过这个标准。

For most humans – living in modern societies with all the trappings of technology and electricity – the amount of time they spend kipping is between six and eight hours a night. So not only did our ancestors not sleep longer than we do, but they may have got slightly less sleep than some of us.

大多数生活在现代社会、享受着科技和电力带来的种种便利的现代人类,每晚的睡眠时间介于6到8小时之间。由此可见,我们祖先的睡眠时间不仅不比现代人长,甚至还不如某些现代人。

We also generally sleep in the comfort of our climate-controlled homes, on comfy mattresses with fluffy pillows, where our biggest worry is who is hogging the covers and whether to allow Fido to sleep on the bed too. Our human ancestors slept instead on rocks, dirt or possibly on tree branches, without the creature comforts of down comforters or central heating. They could not use blackout blinds to let them lie in long after the sun came up, nor could they hope to avoid weather or insects. They also had to worry about being picked off by the occasional predator or attacked by a rival group while they slept. It's no wonder they likely got little more than six hours each night.

我们一般在配备空调的卧室里睡眠,身下铺着舒适的床垫,枕着松软的枕头,唯一要担心的是睡梦中被子可能被伴侣抢走,还有是否让宠物狗上床共眠。然而,我们的祖先却只能在岩石、泥土或者树枝上入睡,没有羽绒被和中央供暖系统带来的舒适。没有窗帘在太阳升起后保持室内黑暗,也无法抵御风雨和昆虫侵袭。此外,不期而至的野兽或者敌对部落也会在我们的祖先入睡时发动袭击。难怪他们每晚的睡眠时间很少能超过6个小时。

Yet there is another myth about how our ancestors slept – that they napped in several short chunks through the night, rather than in one long slumber. On that too, according to Siegel, we're wrong. This erroneous assumption, he blames on our pets.

关于人类祖先的睡眠还有另外一个传言——他们晚上时睡时醒,睡眠被分割成几段,不会睡上一个完整的觉。西格尔说,这种说法也是不符合事实的。他说,人们是看到宠物的睡眠状况才有这种想象的。

"I think the origin of that [idea] is people have cats and dogs, and that's what cats and dogs do – they do sleep that way," he says. "But primates don't." We are but the latest in a long line of species that tends to snooze in one long, uninterrupted block of sleep each night. That's not to say that apes and monkeys don’t take the occasional mid-day nap, or that they don't wake up in the middle of the night from time to time. But, just like in our own species, that's not quite the norm.

"饲养猫狗作为宠物的人看到猫狗这样睡觉,就以为人类的祖先也是这样,"他说。"但是原始人不会这样睡。"人类是一系列保持完整睡眠的物种中进化得最晚的一个。猩猩和猿猴也会在白天打盹或者在半夜醒来。但是和人类一样,这些现象都不是常态。"

Indeed, Siegel's cross-cultural study found that modern hunter-gatherer groups almost never napped in the winter, and only napped slightly more often during the summer, presumably as a means of escaping the worst heat of the day. And even then, he says, the average person only took a daytime nap every fifth day or so.

西格尔的跨文化研究发现,现代狩猎/采摘部落在冬天几乎从不打盹,在夏天打盹的次数稍多,这可能是算避开白天最热的时段的途径。但是他说,即便如此,平均每人每5天里才会打盹一次。

But there is one tiny way in which the myth holds up. The people Siegel studied all lived fairly close to the equator. As you move to higher latitudes, the night can last up to 16 hours in the winter, so living in that kind of environment may have led Northern European ancestors to fragment their evening slumber during that part of the year. But because we have cleaved our sleep patterns from the natural cycles of the seasons, even in Northern Europe most modern-day humans sleep through the night, perhaps just waking up for a quick visit to the bathroom.

但是,传言可能有一点点对的地方。西格尔所研究的部落全都位于赤道附近。在高纬度地区,冬季夜晚会长达16小时。在这种环境下生存的北欧原始人很有可能在冬季夜晚时睡时醒。然而,现代人已经不再按照四季的自然节律入睡。哪怕在北欧地区,大多数现代人也不会在冬夜中断睡眠,顶多半夜起来去上次厕所而已。

Having settled two of the most pervasive myths regarding sleep behaviour, Siegel has now turned to other, more fundamental questions about the nature of sleep. Why do we even do it?

否定了关于睡眠行为的两个最流行的传言后,西格尔现在开始把注意力投向关于睡眠的另一个更为根本性的问题。我们为什么必须睡觉?

If it played a role in memory consolidation or some other brain function, then you wouldn’t expect the big brown bat to get a whopping 20 hours a day, while the much larger and cognitively complex African elephant survives comfortably on just two.

如果睡眠是为了强化记忆或其他大脑功能的话,那么如何解释大棕蝙蝠每天要呼呼大睡20小时,然而体型巨大、智力更强的非洲象只需睡上2小时就足够呢?

Instead, Siegel wonders whether sleep may not be a biological requirement itself, but rather evolution's way of maximising productivity. As he wrote in Nature Reviews Neuroscience in 2009, perhaps sleep provides a means of "increas[ing] the efficiency of behavior by regulating its timing and by reducing energy use when activity is not beneficial."

西格尔认为,睡眠本身可能并非一种生物学需求,而是在进化过程中产生的、实现生产力最大化的一种行为。他在2009年发表于《神经科学自然评论》(Nature Reviews Neuroscience)杂志上的一篇论文中写道,睡眠的作用可能是"在生物活动不再有益的时间段,通过优化时间使用及降低能量用量而提高行为效率"。

It's a common trick in both the animal and plant kingdoms. Some trees shed their leaves in the autumn and cease photosynthesising, which could be thought as a kind of botanical slumber. Bears hibernate in the winter, in part to avoid fruitlessly expending energy hunting and foraging at a time when there is not much food to be found.

无论在动物界还是植物界,这都是一种十分常见的生存策略。有些树会在秋天会脱去树叶并停止光合作用,这可以看作是一种植物冬眠。熊在冬季会冬眠,从而避免在食物匮乏的季节徒劳无功地四处捕猎和觅食。

Other mammals, such as echidnas, enter a sleepy-state known as torpor, where their metabolism slows down to barely a whisper to help them get through hard times. Perhaps sleep is simply our version of such "adaptive inactivity", allowing us to be productive during the daylight hours while avoiding overexertion - and, historically, exposure to predators - at night, while still permitting us to awaken easily if necessary.

其他哺乳动物,例如针鼹鼠(echidnas)在食物匮乏的季节会进入一种昏昏欲睡的"麻木"(torpor)状态,这种状态下,针鼹鼠的新陈代谢率会大幅下降。而睡眠可能是人类的一种"适应性活动抑制"(adaptive inactivity)行为,它让我们在白天保持清醒,在晚上则避免过分活动引来捕食动物。必要时,还可以让我们在夜间迅速醒来。

Or, to put it another way, maybe it's selective laziness.

换句话说,睡眠可能是一种"选择性懒惰"(selective laziness)。

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