Why can't some people remember their dreams?
为什么有些人记不住自己的梦？

I am standing outside my childhood primary school, near the front gates and the teachers’ car park. It is a bright sunny day and I am surrounded by my classmates. There must be more than a hundred of us.

我站在小时候就读的小学外面，旁边是学校大门和教师停车场。阳光明媚，我周围都是同学，现场肯定有100多人。

I have a dim feeling that some of my teachers are nearby, but my attention is on two adults, neither of which I recognise. The man I see in lurid detail – from the slick shine of his hair to the golden lenses on his sunglasses. He holds up some kind of device that emits a piercing shriek. I drop to my knees with my hands against my ears. My schoolmates are all doing the same. The man is laughing maniacally.

我隐约感觉一些教过我的老师就在附近，但我的注意力集中在两个我不认识的成年人身上。那个男的我看得清清楚楚——从他头发的光泽到太阳镜上的金色镜片。他举起的某种设备发出刺耳的声音，我跪倒在地，双手捂着耳朵。同学们都做着相同的动作，那人却在狂笑。

I had that dream nearly 40 years ago, but I can remember the details as if it were yesterday. Ask me to relate anything from a dream I had earlier this week, however, and I draw a blank. If I have been dreaming – and biology would suggest I most probably have – nothing has lingered long enough to remain in my waking mind.

这个梦是我在大概40年前做的，但我记得所有细节，就像发生在昨天一样。然而，如果让我描述几天前的梦，我的脑海却是一片空白。如果我一直在做梦——并且生理特性表明我极有可能的确一直在做梦——梦中的一切存留的时间都不足以让我在醒后仍记得。

For many of us, dreams are an almost intangible presence. If we’re lucky, we can only remember the most fleeting glimpse in the cold light of day; even those of us who can recollect past dreams in astonishing detail can wake some days with almost no memory of what we had dreamed about.

对我们很多人来说，梦几乎是一种无形的存在。如果运气好，我们只能在平静下来后记住最短暂的一幕；即便是有些人能以惊人的详细程度回忆自己做过的梦，但有时醒来后也几乎不记得自己梦到什么了。

There is little ethereal about the reasons this might be happening, however. Why we have dreams – and whether we can remember them – are both rooted in the biology of our sleeping bodies and subconscious mind.

然而，其原因没什么神秘的。我们为什么会做梦——以及我们是否能记住自己的梦——都源于我们睡觉时身体和潜意识的生理特性。

Sleep is more complicated than we once thought. Rather than being a plateau of unconsciousness bookended by slipping in and out of sleep, our resting brains go through a rollercoaster of mental states, with some parts being full of mental activity.

睡眠比我们曾经以为的要复杂得多。在我们睡着时，休眠的大脑并非处于因时睡时醒而被分割成多个阶段的无意识且稳定的状态，而是会经历一系列急剧变化的精神状态。在其中一些阶段，我们的心理活动极其丰富。

Dreaming is most closely associated with the sleep state known as Rapid Eye Movement (REM). REM is sometimes known as desychronised sleep, because it can mimic some of the signs of being awake. In REM sleep, the eyes twitch rapidly, there are changes in breathing and circulation, and the body enters a paralysed state known as atonia. It happens in 90-minute-waves during sleep, and it’s at this stage that our brains tend to dream.

做梦和名为“快速眼动”（Rapid Eye Movement ，REM）的睡眠状态关系最为密切。快速眼动有时又被称做“去同步睡眠”，因为它能模拟一些醒着时的迹象。在快速眼动睡眠中，眼球快速移动，人体的呼吸和循环发生变化，身体进入一种名为弛缓（atonia）的瘫痪状态。在睡眠中，这种状态会以90分钟为周期循环出现。我们的大脑往往会在这个阶段做梦。

There is an extra flow of blood to crucial parts of our brain during the REM state: the cortex, which fills our dreams with their content, and the limbic system, which processes our emotional state. While we’re in this dream-friendly state of sleep, they fire with furious electrical activity. The frontal lobes, however – which direct our critical faculties – are quiet.

在快速眼动睡眠阶段，会有额外的血液流向大脑的关键部位：脑皮层和大脑边缘系统。脑皮层为我们的梦提供内容，大脑边缘系统则负责处理我们的情绪状态。当我们处于这种有利于做梦的睡眠状态时，这两个地方充斥着激烈的脑电活动。然而，掌控辨别能力的额叶却一片沉寂。

This means we often blindly accept what is happening in this often nonsensical narrative until the time comes to wake up.

这意味着我们常常会盲目接受没有意义的叙述，直到醒来。

The problem is, the more jumbled the imagery, the harder it is for us to grasp hold of. Dreams that have a clearer structure are much easier for us to remember, psychology professor and author Deidre Barrett said in a recent story on Gizmodo.

问题是，梦境越混乱，我们越难掌握。前不久，心理学教授兼作家巴雷特（Deidre Barrett）在发表在Gizmodo上的一篇文章中称，梦的结构越清晰，我们越容易记住。

But there’s a chemical component at work which is crucial for making sure those dream images are retained: noradrenaline. Noradrenaline is a hormone that primes the body and mind for action, and our levels of it are naturally lower in deep sleep.

但有一种化学成分起了作用，它能确保我们记住梦中的画面：去甲肾上腺素（noradrenaline）。去甲肾上腺素是一种激素，负责让身体和大脑为行动做好准备。在深度睡眠中，我们体内的去甲肾上腺素水平自然比较低。

Francesca Siclari, a sleep research doctor at the Lausanne University Hospital, says there are clear definitions between our states of wake and sleep – and that is no accident. “It’s probably a good thing that the dream life and the waking life are completely different,” she says.

洛桑大学医院（Lausanne University Hospital）研究睡眠的医生西克拉里（Francesca Siclari）说，我们在清醒和睡眠状态之间有着清晰的界定，这并非偶然。“梦中的生活和现实生活完全不同，这可能是件好事，”她说。

“I think if you remembered every detail like you can do in waking life, you would start to confuse things with what’s actually happening in your real life.”

“我觉得，如果能像在现实生活中一样记住每一个细节，你就会把梦境和现实生活中发生的事情混淆在一起。”

She says that people suffering from sleep disorders, such as narcolepsy, can find it difficult to tell the difference between their waking and sleeping lives, and this can leave them feeling confused and embarrassed. “There are also people who remember their dreams too well, and they actually start exporting those memories into their day.”

她说，患有睡眠障碍，如嗜睡症的人，可能会觉得难以区分清醒和睡着时的生活，而这可能会使他们感到迷茫和尴尬。“也有一些人对自己的梦记得非常清楚，他们实际上会开始把这些记忆输出到自己的日常生活中去。”

It is no accident that the dreams we remember the most come from certain periods in our sleep cycle, affected by the chemicals coursing through our sleeping bodies. “Normally we dream most vividly in REM sleep, which is when the levels of noradrenaline are low in the brain,” she says.

我们记得最清楚的梦来自睡眠周期中的特定阶段，并受一些快速流经人体的化学物质的影响，这并非偶然。“通常情况下，我们在快速眼动睡眠中做的梦最清晰，在这个阶段，大脑去甲肾上腺素水平较低，”她说。

We may find ourselves dreaming right before we wake up – but our morning routines actually get in the way of remembering the imagery. Often we are startled out of our slumber by an alarm clock, which causes a spike in our noradrenaline levels – thus making it harder for us to hang onto our dreams.

我们可能会觉得自己醒来前正在做梦——但早上的常规实际上妨碍了我们对梦的记忆。我们常常是被闹钟从睡梦中惊醒的，这导致去甲肾上腺素水平飙升，进而加大了我们记住梦的难度。

“Someone who asks me the question of why they can’t remember their dreams, I say it’s because they fall asleep too fast, sleep too soundly and wake up with their alarm clock,” says Harvard Medical School sleep researcher Robert Stickgold. “And their response is usually, ‘How did you know that?’”

“有人问我为什么记不住自己的梦，我说那是因为他们入睡太快、睡得太沉而醒来时又是被闹钟叫醒的，”哈佛大学医学院（Harvard Medical School）的睡眠研究人员斯蒂克戈尔德（Robert Stickgold）说。“他们的反应通常是，‘你怎么知道的？’”

Stickgold says that a lot of people remember their dreams from a sleep onset period, when the mind starts wandering and dreamlike imagery occurs as people drift in and out of sleep – a process called “hypnagogic dreaming”. Stickgold says he carried out a study some years ago where students in a lab were awoken shortly after they started entering this state. “Every last one of them remembered dreaming,” he says.

斯蒂克戈尔德说，很多人记得自己在睡眠开始阶段做的梦。在这个阶段，人们处于半睡半醒的状态，思绪开始恍惚，梦境出现——这个过程叫“入睡前做梦”。斯蒂克戈尔德说，多年前他做过一项研究：在一个实验室里，学生们在开始进入这种状态后不久即被叫醒。“他们每个人都记得自己在做梦，”他说。

“This stage is the first five or 10 minutes after falling asleep. If you just fall fast asleep – the way we all wish we could – you’re not going to remember anything from that part of your sleep cycle.”

“这个阶段是入睡后的最初5到10分钟。如果你入睡很快——我们所有人都希望自己是这样——在这个睡眠阶段发生的所有事情你都记不住。”

So what if you actively want to remember your dreams? Obviously, each sleeper is different, but there are some general tips which might help you to hold on to your dreams.

那么，如果你主动想记住自己的梦呢？显然，每个人都不一样，但有一些通用的建议可能有助于你记住自己的梦。

“Dreams are incredibly fragile when we first wake up, and we don’t really have an answer for why that is,” says Stickgold. “If you’re the kind of person who leaps up out of bed and goes about their day, you’re not going to remember your dreams. When you sleep in on a Saturday or Sunday morning, that’s an excellent time to remember dreams.

“在我们刚醒的时候，梦非常脆弱，我们真的不知道为什么会这样，”斯蒂克戈尔德说。“如果你是那种从床上一跃而起，直接开始一天生活的人，那么你是不会记得自己的梦的。如果你在周六或周日早上睡懒觉，这是记住梦的绝佳时间。”

“What I tell my students on my courses is, when you wake up, try to lie still – don’t even open your eyes. Try to ‘float’ and at the same time try to remember what was in your dream. What you’re doing is you’re reviewing dreams as you enter your waking state and you’ll remember them just like any other memory.”

“我在课上告诉学生，醒了以后，躺着别动，甚至不要睁眼，试着‘漂浮’，同时试着回忆梦里发生了什么。这么做其实是在进入清醒状态时回顾你做过的梦，你会像其他记忆一样记住它们。”

There are even more surefire ways to remember dreams, Stickgold says. “I tell people to drink three big glasses of water before they go to bed. Not three glasses of beer, because alcohol in an REM suppressant, but water. You’ll wake up three or four times in the night and you’ll tend to wake up at the end of an REM cycle of sleep which is natural.”

甚至还有更加万无一失的记住梦的办法，斯蒂克戈尔德说。“我让人们在睡前喝三大杯水，不是三杯啤酒，因为酒精会抑制快速眼动睡眠，是水。这样你就会在夜里醒三、四次，并且往往是在自然的快速眼动睡眠周期结束时醒来。”

And there is another piece of advice offered by some sleep researchers – that simply repeating to yourself as you drift towards sleep that you want to remember your dreams means you wake remembering them. Stickgold laughs. “It actually works. If you do that you really are going to remember more dreams, it’s like saying ‘There’s no place like home’. It really works.”