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Ever since Charles Darwin published On the Origin of Species in 1859, evolution has been the grand unifying theory of biology. Yet one of our most important biological traits, consciousness, is rarely studied in the context of evolution. Theories of consciousness come from religion, from philosophy, from cognitive science, but not so much from evolutionary biology. Maybe that’s why so few theories have been able to tackle basic questions such as: What is the adaptive value of consciousness? When did it evolve and what animals have it?

The Attention Schema Theory (AST), developed over the past five years, may be able to answer those questions. The theory suggests that consciousness arises as a solution to one of the most fundamental problems facing any nervous system: Too much information constantly flows in to be fully processed. The brain evolved increasingly sophisticated mechanisms for deeply processing a few select signals at the expense of others, and in the AST, consciousness is the ultimate result of that evolutionary sequence. If the theory is right—and that has yet to be determined—then consciousness evolved gradually over the past half billion years and is present in a range of vertebrate species.

自从查尔斯·达尔文(Charles Darwin)在1859年发表《物种起源》以来,进化一直都是生物学的大统一理论。然而,虽然意识是人类的一个最重要的生物学特征,但是人们很少在进化的背景下研究人类意识。关于意识的理论来自于宗教、哲学与认知科学几个领域,但是进化生物学并不包括在内。或许,这就是为什么很少有理论可以解释“意识的适应价值是什么?”、“意识是什么时候进化出来的?”、“哪些动物具备意识?”等这类基本问题。

过去五年期间发展出来的“注意图示理论”(Attention Schema Theory,简称AST)也许能够回答这些问题。根据这一理论,意识是动物为了解决任何神经系统所面临的一个最基本的问题而进化出来的解决方法:大量信息不断涌入大脑,多得大脑无法对之进行完整处理。大脑为了对某些特定信号进行深度处理,同时忽略其他信号,而进化出了越来越复杂的机制。在注意图示理论中,意识便是这种进化顺序的最终结果。如果这一理论正确(至于是否正确则有待确定),意识在过去5亿年期间渐渐演化出来,而且存在于一系列脊椎动物物种中。

纠正翻译

Neurons act like candidates in an election, each one shouting and trying to suppress its fellows.

Even before the evolution of a central brain, nervous systems took advantage of a simple computing trick: competition. Neurons act like candidates in an election, each one shouting and trying to suppress its fellows. At any moment only a few neurons win that intense competition, their signals rising up above the noise and impacting the animal’s behavior. This process is called selective signal enhancement, and without it, a nervous system can do almost nothing.

我们可以利用进化生物学的一个常见方法,很好地猜测出选择性信号增强首次进化出来的时间:对不同动物种类进行比较。水螅(Hydra)是水母的一个亲戚,体积非常小,可以说是拥有已知最简单的神经系统:神经网。如果在水螅身上任何部位戳一下,它就会做出全身性的反应。没有任何证据显示,它能在选择性地处理某些“戳”的同时,策略性地忽略其他“戳”。根据基因分析,水螅和其他动物的祖先之间的分歧,有可能早在7亿年前就发生了。因此,选择性信号增强应该是在此之后进化出来的。

纠正翻译

We can take a good guess when selective signal enhancement first evolved by comparing different species of animal, a common method in evolutionary biology. The hydra, a small relative of jellyfish, arguably has the simplest nervous system known—a nerve net. If you poke the hydra anywhere, it gives a generalized response. It shows no evidence of selectively processing some pokes while strategically ignoring others. The split between the ancestors of hydras and other animals, according to genetic analysis, may have been as early as 700 million years ago. Selective signal enhancement probably evolved after that.

接下来的进化步骤,是一个能够在所有感官之间进行协调的中央集中力控制器。许多动物的中央集中力控制器是大脑中一个叫做“顶盖”(tectum)的区域。(在拉丁文中,“tectum”就是“顶盖”的意思,而顶盖通常盖住了大脑的顶部。)它为一个叫做“外显注意力”(overt attention)的功能进行协调,也就是说,它负责把眼睛、耳朵与鼻子的“卫星碟”瞄准任何重要的东西。

所有脊椎动物(鱼、爬行动物、鸟类、哺乳动物)都有顶盖。就连七鳃鳗也有顶盖,而且七鳃鳗在进化史上出现得非常早,早得连下颚都没有。但是就任何人所知,所有无脊椎动物都缺乏顶盖。脊椎动物有顶盖、无脊椎动物没有顶盖这一事实,使我们能够判断它进化出来的时间。根据化石和遗传证据,脊椎动物是在大约5.2亿年前进化出来的。所谓的“寒武纪生命大爆发”(Cambrian Explosion)差不多是在这个时候发生的,当时,脊椎动物体型非常小,身体只会扭动,必须在海中与许多无脊椎动物竞争,而顶盖和中央集中力控制器大概就是在这个时候进化出来的。

纠正翻译


The arthropod eye, on the other hand, has one of the best-studied examples of selective signal enhancement. It sharpens the signals related to visual edges and suppresses other visual signals, generating an outline sketch of the world. Selective enhancement therefore probably evolved sometime between hydras and arthropods—between about 700 and 600 million years ago, close to the beginning of complex, multicellular life. Selective signal enhancement is so primitive that it doesn’t even require a central brain. The eye, the network of touch sensors on the body, and the auditory system can each have their own local versions of attention focusing on a few select signals.

另一方面,节肢动物的眼睛是选择性信号增强的一个最佳研究实例。它会把视觉边缘的相关信号锐化,同时把其它视觉信号抑制下来,从而产生世界的轮廓草图。因此,选择性信号增强应该是在水螅和节肢动物之间(大约6-7亿年前)进化出来的,这段时间接近复杂的多细胞生命开始出现的时候。选择性信号增强非常原始,连中央大脑也不需要。眼睛、身上的触觉感受器网络、听觉系统,本身就能够只把注意力放在几个特定信号上。

纠正翻译


The next evolutionary advance was a centralized controller for attention that could coordinate among all senses. In many animals, that central controller is a brain area called the tectum. (“Tectum” means “roof” in Latin, and it often covers the top of the brain.) It coordinates something called overt attention – aiming the satellite dishes of the eyes, ears, and nose toward anything important.


All vertebrates—fish, reptiles, birds, and mammals—have a tectum. Even lampreys have one, and they appeared so early in evolution that they don’t even have a lower jaw. But as far as anyone knows, the tectum is absent from all invertebrates. The fact that vertebrates have it and invertebrates don’t allows us to bracket its evolution. According to fossil and genetic evidence, vertebrates evolved around 520 million years ago. The tectum and the central control of attention probably evolved around then, during the so-called Cambrian Explosion when vertebrates were tiny wriggling creatures competing with a vast range of invertebrates in the sea.

接下来的进化步骤,是一个能够在所有感官之间进行协调的中央集中力控制器。许多动物的中央集中力控制器是大脑中一个叫做“顶盖”(tectum)的区域。(在拉丁文中,“tectum”就是“顶盖”的意思,而顶盖通常盖住了大脑的顶部。)它为一个叫做“外显注意力”(overt attention)的功能进行协调,也就是说,它负责把眼睛、耳朵与鼻子的“卫星碟”瞄准任何重要的东西。

所有脊椎动物(鱼、爬行动物、鸟类、哺乳动物)都有顶盖。就连七鳃鳗也有顶盖,而且七鳃鳗在进化史上出现得非常早,早得连下颚都没有。但是就任何人所知,所有无脊椎动物都缺乏顶盖。脊椎动物有顶盖、无脊椎动物没有顶盖这一事实,使我们能够判断它进化出来的时间。根据化石和遗传证据,脊椎动物是在大约5.2亿年前进化出来的。所谓的“寒武纪生命大爆发”(Cambrian Explosion)差不多是在这个时候发生的,当时,脊椎动物体型非常小,身体只会扭动,必须在海中与许多无脊椎动物竞争,而顶盖和中央集中力控制器大概就是在这个时候进化出来的。

纠正翻译


Even if you’ve turned your back on an object, your cortex can still focus its processing resources on it.


The tectum is a beautiful piece of engineering. To control the head and the eyes efficiently, it constructs something called an internal model, a feature well known to engineers. An internal model is a simulation that keeps track of whatever is being controlled and allows for predictions and planning. The tectum’s internal model is a set of information encoded in the complex pattern of activity of the neurons. That information simulates the current state of the eyes, head, and other major body parts, making predictions about how these body parts will move next and about the consequences of their movement. For example, if you move your eyes to the right, the visual world should shift across your retinas to the left in a predictable way. The tectum compares the predicted visual signals to the actual visual input, to make sure that your movements are going as planned. These computations are extraordinarily complex and yet well worth the extra energy for the benefit to movement control. In fish and amphibians, the tectum is the pinnacle of sophistication and the largest part of the brain. A frog has a pretty good simulation of itself.

就算你已经转身,背部正朝向某个东西,你的皮层依然能将脑力专注在处理这个东西上。

顶盖是一件设计得非常完美的机器。为了有效率地控制头部和眼睛,它会构造一个叫做“内部模型”(internal model)的东西,凡是工程师都非常熟悉这一功能。所谓内部模型,就是一个会追踪其所控制的器官,并允许进行预测和规划的模拟。顶盖的内部模型,就是记录在神经元的复杂活动模式中的一套信息。这些信息模拟了眼睛、头部以及其它主要身体部位的当前状态,还会预测这些部位接下来的动作,以及这些动作的后果。比如,你如果将眼睛向右移动,视网膜上的视觉世界就会以可预见的方式往左移动。顶盖会对预料中的视觉信号和实际视觉输入进行比较,以确保你的动作正在按计划进行。这些计算虽然极其复杂,但是花些额外精力来改善对动作的控制,绝对是值得的。在鱼类和两栖动物中,顶盖是大脑的最大部位,而且极为复杂。青蛙能够很真实地模拟自己。

纠正翻译


With the evolution of reptiles around 350 to 300 million years ago, a new brain structure began to emerge – the wulst. Birds inherited a wulst from their reptile ancestors. Mammals did too, but our version is usually called the cerebral cortex and has expanded enormously. It’s by far the largest structure in the human brain. Sometimes you hear people refer to the reptilian brain as the brute, automatic part that’s left over when you strip away the cortex, but this is not correct. The cortex has its origin in the reptilian wulst, and reptiles are probably smarter than we give them credit for.

随着爬行动物在大约3-3.5亿年前进化出来,一个新的大脑结构开始出现了,那就是视丘(wulst)。鸟类从它们的爬行动物祖先那里遗传了一个视丘。哺乳动物也是这样,但是我们的视丘通常叫做“大脑皮层”,而且它已经变大了许多。到目前为止,它是人脑中最大的结构。有时候,你会听到有人把爬行动物的大脑称为“大脑剥下皮层后所剩下的野蛮、无意识的部分”,但这是不正确的说法。大脑的皮层起源于爬行动物的视丘,而爬行动物很可能比我们想像中还要聪明。

纠正翻译


The cortex is like an upgraded tectum. We still have a tectum buried under the cortex and it performs the same functions as in fish and amphibians. If you hear a sudden sound or see a movement in the corner of your eye, your tectum directs your gaze toward it quickly and accurately. The cortex also takes in sensory signals and coordinates movement, but it has a more flexible repertoire. Depending on context, you might look toward, look away, make a sound, do a dance, or simply store the sensory event in memory in case the information is useful for the future.

皮层就像是一个经过升级的顶盖。我们的皮层下仍然埋着一个顶盖,而这个顶盖所扮演的功能,跟鱼类和两栖动物是一样的。如果你听到一个突然发出的声音,或者眼角看到有动作,你的顶盖就会迅速、准确地把你的目光对准它。皮层也会接收感觉信号,还会对动作进行协调,但是它的功能比这还要灵活。皮层接收到感觉信号后,你会根据具体情况做出不同反应。你也许会看着它、往别处看、发出声音、跳个舞、或者只是把它储存在记忆中,以防在未来需要用到这一信息。

纠正翻译


The most important difference between the cortex and the tectum may be the kind of attention they control. The tectum is the master of overt attention—pointing the sensory apparatus toward anything important. The cortex ups the ante with something called covert attention. You don’t need to look directly at something to covertly attend to it. Even if you’ve turned your back on an object, your cortex can still focus its processing resources on it. Scientists sometimes compare covert attention to a spotlight. (The analogy was first suggested by Francis Crick, the geneticist.) Your cortex can shift covert attention from the text in front of you to a nearby person, to the sounds in your backyard, to a thought or a memory. Covert attention is the virtual movement of deep processing from one item to another.

皮层和顶盖之间最重要的区别,可能就是两者所控制的注意力种类。顶盖精通的是外显注意力,它会把感官对准重要的东西。皮层则是更上一层楼;它负责的是一个叫做“隐蔽注意力”(covert attention)的功能。你不需要直视某样东西,也能隐蔽地处理它。就算你已经转身,背部正朝向某个东西,你的皮层依然能将脑力专注在处理这个东西上。科学家有时候会把隐蔽注意力形容成一盏聚光灯。(这一比喻最早由遗传学家弗朗西斯·克里克(Francis Crick)提出。)你的皮质可以将隐蔽注意力从你面前的文字,转移到附近的一个人,或者你家后院里的声音,或者一个思想、一个记忆。隐蔽注意力是大脑将深度处理活动从某个东西虚拟转移到另一个东西的能力。

纠正翻译


The cortex needs to control that virtual movement, and therefore like any efficient controller it needs an internal model. Unlike the tectum, which models concrete objects like the eyes and the head, the cortex must model something much more abstract. According to the AST, it does so by constructing an attention schema—a constantly updated set of information that describes what covert attention is doing moment-by-moment and what its consequences are.


“I’ve got something intangible inside me. It’s not an eyeball or a head or an arm. It exists without substance …”

皮层必须控制住这种虚拟的转移活动,因此,它就像任何高效的控制器一样,需要有一个内部模型。与顶盖不同的是,顶盖会为眼睛、头部等具体物件描绘一个模型,而皮层则必须为一个抽象得多的东西描绘模型。根据注意图示理论,皮层采用的做法,就是构造一个“注意图示”,也就是一组不断更新的信息集,它形容了隐蔽注意力每时每刻处理的东西,以及这些活动的后果。

“我脑海中有个无形的东西。它不是眼球,也不是头,也不是手臂。它的存在是没有实质的……”

纠正翻译


Consider an unlikely thought experiment. If you could somehow attach an external speech mechanism to a crocodile, and the speech mechanism had access to the information in that attention schema in the crocodile’s wulst, that technology-assisted crocodile might report, “I’ve got something intangible inside me. It’s not an eyeball or a head or an arm. It exists without substance. It’s my mental possession of things. It moves around from one set of items to another. When that mysterious process in me grasps hold of something, it allows me to understand, to remember, and to respond.”

我们来进行一个思想实验,想一个不太可能发生的事。假设你有办法给一条鳄鱼安装一架外部说话器,而这架说话器能够读取得到鳄鱼视丘的注意图示中的信息。那么,这条得到了技术帮助的鳄鱼可能会说:“我大脑中有个无形的东西。它不是眼球,也不是头,也不是手臂。它的存在是没有实质的。它是我在大脑中所拥有的东西。它会从一组东西来回转移到另一组东西。当我大脑中这个神秘的过程掌握住某样东西的时候,我就能够明白,能够记得,能够反应。”

纠正翻译


The crocodile would be wrong, of course. Covert attention isn’t intangible. It has a physical basis, but that physical basis lies in the microscopic details of neurons, synapses, and signals. The brain has no need to know those details. The attention schema is therefore strategically vague. It depicts covert attention in a physically incoherent way, as a non-physical essence. And this, according to the theory, is the origin of consciousness. We say we have consciousness because deep in the brain, something quite primitive is computing that semi-magical self-description. Alas crocodiles can’t really talk. But in this theory, they’re likely to have at least a simple form of an attention schema.

这条鳄鱼的说法当然是错的。隐蔽注意力并不是无形的。它是有物质依据的,但是这一物质依据在于神经元、突触和信号的微小细节。大脑没有必要知道这些细节,因此,它的注意图示非常含糊,是有策略原因的。它是非物理本质的,所以会以不符合物理的方式把隐蔽注意力描绘出来。根据注意图示理论,这就是意识的起源。之所以说我们有意识,是因为有一个非常原始的力量正在大脑的深处计算出这个半神奇的自我描述。可惜的是,鳄鱼其实不会说话,但是在这一理论中,它们很可能至少具备某种简单的注意图示。

纠正翻译


When I think about evolution, I’m reminded of Teddy Roosevelt’s famous quote, “Do what you can with what you have where you are.” Evolution is the master of that kind of opportunism. Fins become feet. Gill arches become jaws. And self-models become models of others. In the AST, the attention schema first evolved as a model of one’s own covert attention. But once the basic mechanism was in place, according to the theory, it was further adapted to model the attentional states of others, to allow for social prediction. Not only could the brain attribute consciousness to itself, it began to attribute consciousness to others.

我一想到进化,就会想起泰迪·罗斯福(Teddy Roosevelt)的一段著名的话:“不管你身在哪里,你都要用你所拥有的东西,做你能做的事。”进化充分掌握了这样的机会主义:鳍进化成了脚、 鳃弧进化成了颚、自我模型进化成了他人的模型。在注意图示理论中,注意图示最初是一个进化出来的自身隐蔽注意力模型。但是,根据这一理论,这个基本机制形成之后,它还发生了进一步调整,目的是模仿他人的注意力状态,以便进行社会预测。大脑不但能够给自己赋予意识,还能给他人赋予意识。

纠正翻译


If a basic ability to attribute awareness to others is present in mammals and in birds, then it may have an origin in their common ancestor, the reptiles.


When psychologists study social cognition, they often focus on something called theory of mind, the ability to understand the possible contents of someone else’s mind. Some of the more complex examples are limited to humans and apes. But experiments show that a dog can look at another dog and figure out, “Is he aware of me?” Crows also show an impressive theory of mind. If they hide food when another bird is watching, they’ll wait for the other bird’s absence and then hide the same piece of food again, as if able to compute that the other bird is aware of one hiding place but unaware of the other. If a basic ability to attribute awareness to others is present in mammals and in birds, then it may have an origin in their common ancestor, the reptiles. In the AST’s evolutionary story, social cognition begins to ramp up shortly after the reptilian wulst evolved. Crocodiles may not be the most socially complex creatures on earth, but they live in large communities, care for their young, and can make loyal if somewhat dangerous pets.

假如哺乳动物和鸟类拥有给其它生物赋予意识的基本能力,那么这个能力有可能来自两者的共同祖先,即爬行动物。

通常,在研究社会认知的时候,心理学家就会关注一个叫做“心理理论”(theory of mind)的能力。所谓心理理论,就是一个生物理解另一个生物的大脑可能含有的内容的能力。只有人类和猿类拥有较复杂的心理理论能力,但是实验显示,一只狗可以看着另一只狗,然后心想:“它意识到了我的存在吗?”乌鸦的心理理论也令人印象深刻。如果乌鸦在另一只鸟的目光下把食物藏起来,它们就会等到这只鸟离开后,再次把同一块食物藏起来。这样的行为代表着,乌鸦似乎能够猜出另一只鸟只知道其中一个藏食物处的所在,不知道另一个藏食物处的所在。假如哺乳动物和鸟类拥有给其它生物赋予意识的基本能力,那么这个能力有可能来自两者的共同祖先,即爬行动物。注意图示理论以进化作为这一现象的解释:在爬行动物的视丘进化出来的不久之后,社会认知就开始急速增加了。鳄鱼虽然不是地球上社交结构最复杂的生物,但是他们生活在很大的社区中,还会照顾幼小;如果把它们当作宠物,它们就会很忠诚,只不过它们也许危险了些。

纠正翻译


If AST is correct, 300 million years of reptilian, avian, and mammalian evolution have allowed the self-model and the social model to evolve in tandem, each influencing the other. We understand other people by projecting ourselves onto them. But we also understand ourselves by considering the way other people might see us. Data from my own lab suggests that the cortical networks in the human brain that allow us to attribute consciousness to others overlap extensively with the networks that construct our own sense of consciousness.


Language is perhaps the most recent big leap in the evolution of consciousness. Nobody knows when human language first evolved. Certainly we had it by 70 thousand years ago when people began to disperse around the world, since all dispersed groups have a sophisticated language. The relationship between language and consciousness is often debated, but we can be sure of at least this much: once we developed language, we could talk about consciousness and compare notes. We could say out loud, “I’m conscious of things. So is she. So is he. So is that damn river that just tried to wipe out my village.”

如果注意图示理论属实的话,爬行动物、禽类和哺乳动物3亿年来的进化,已经让自我模型和社交模型发生了同步进化,并使两者在进化过程中互相影响。我们会把自己投射在别人身上来理解他们,但是我们也会通过考虑别人看待我们的方式来理解自己。我自己的实验室的数据表明,人脑皮质中使人类给他人赋予意识的神经网络,与构建自身意识的网络,在很大程度上是相互重叠的。

语言,也许就是意识的进化史上最迟出现的大跃进。没有人知道人类语言什么时候首次进化出来。我们可以肯定,人类在7万年前就有了语言。这是因为,人类是在当时开始分散到世界各地去,而且所有被分散的群体都拥有复杂的语言。语言和意识之间的关系,往往众说纷纭,但是我们至少可以肯定,人类一旦发展出了语言,就能讨论意识的课题,并且彼此交换心得。我们可以大声说:“我对周围环境有意识,她也是,他也是。刚刚差一点摧毁我家乡的那条该死的河,当然也是。”

纠正翻译


If the wind rustles the grass and you misinterpret it as a lion, no harm done. But if you fail to detect an actual lion, you’re taken out of the gene pool.


Maybe partly because of language and culture, humans have a hair-trigger tendency to attribute consciousness to everything around us. We attribute consciousness to characters in a story, puppets and dolls, storms, rivers, empty spaces, ghosts and gods. Justin Barrett called it the Hyperactive Agency Detection Device, or HADD. One speculation is that it’s better to be safe than sorry. If the wind rustles the grass and you misinterpret it as a lion, no harm done. But if you fail to detect an actual lion, you’re taken out of the gene pool. To me, however, the HADD goes way beyond detecting predators. It’s a consequence of our hyper-social nature. Evolution turned up the amplitude on our tendency to model others and now we’re supremely attuned to each other’s mind states. It gives us our adaptive edge. The inevitable side effect is the detection of false positives, or ghosts.

如果风把草吹得沙沙响,你却以为狮子来了,那倒不成问题。但是,要是没发现狮子真的出现,恐怕基因池中从此不再有你。

人类很容易就会给周围万物赋予意识;这一部分可能是语言和文化所致。我们会给故事人物、木偶、娃娃、风暴、河流、空间、鬼神等东西赋予意识。贾斯汀·巴雷特(Justin Barrett)将这种习惯称为“超活跃代理检测装置”(Hyperactive Agency Detection Device)。有些人猜测,人类的本性是“安全至上、防患未然”。如果风把草吹得沙沙响,你却以为狮子来了,那倒不成问题。但是,要是没能发现狮子真的出现,恐怕基因池中从此不再有你。但是,对我来说,“超活跃代理检测装置”并不只是为了检测捕食者的存在而已;此装置的存在,是人类“过度社交”本性的一个后果。进化使我们更倾向模仿他人,而如今,我们已经非常理解彼此的思维状态。这种适应能力给我们带来了优势。但是,这种能力的一个无可避免的副作用,就是我们会检测到假阳性结果,也就是:我们会见到鬼。

纠正翻译


And so the evolutionary story brings us up to date, to human consciousness—something we ascribe to ourselves, to others, and to a rich spirit world of ghosts and gods in the empty spaces around us. The AST covers a lot of ground, from simple nervous systems to simulations of self and others. It provides a general framework for understanding consciousness, its many adaptive uses, and its gradual and continuing evolution.

就这样,人类进化史给人类赋予了我们现在拥有的意识。我们不仅给自己和他人赋予了意识,还给我们周围空间中充满鬼神灵仙的世界赋予了意识。注意图形理论讨论了许多议题,例如简单的神经系统、自我模拟、等等。它为理解意识、意识的适应性用途、以及其逐步持续的进化,提供了一个总体框架。

纠正翻译