Your brain hallucinates your conscious reality | Anil Seth | TED

Summary

在这段演讲中，演讲者探讨了意识的本质和它如何产生的问题。他将意识描述为一种现代魔法，能够将人变成无意识的对象，然后再恢复为有意识的存在。演讲者通过自己的经历和科学实验，阐述了大脑如何通过预测机制来感知世界，以及我们如何通过身体内部的信号来感知自我。他提出，我们的意识体验，包括对世界的感知和自我意识，都是由大脑基于生存需求而生成的“控制幻觉”。演讲者还讨论了意识与智能的区别，并指出意识更与生物体的本性有关。最后，他提出了对意识研究的三个启示：意识的误解可能导致精神疾病，意识不能简单地上传到机器，以及人类意识只是众多可能意识形式中的一种。

Takeaways

• 💉 麻醉是一种现代魔法，它暂时使人失去意识，但与自然睡眠不同，人们在麻醉后无法感知时间的流逝。
• 🧠 意识是如何产生的是科学和哲学中最大的谜团之一，它涉及到大脑中数十亿神经元的复杂活动。
• 🤔 意识和智能是不同的，意识可能与生命体的生物特性有关，而不仅仅是智能。
• 🐕 其他动物可能也具有意识和自我意识，这提示我们意识可能在生物界中广泛存在。
• 💻 尽管计算机越来越智能，但意识的产生可能与生物体的特性密切相关，因此人工智能发展出意识的可能性很小。
• 🧩 意识体验可以被视为一种受控的幻觉，这是通过我们的身体和大脑的预测机制产生的。
• 👁️ 我们的感知是大脑基于先前经验和预期对感官信号的猜测，这解释了为何视觉错觉能够影响我们的感知。
• 🤲 橡胶手幻觉实验表明，大脑通过最佳猜测来确定身体边界，这涉及到视觉、触觉和预期的一致性。
• 🌐 我们对世界的体验不仅仅是外部世界的反映，更多地是由内部的预测和感知机制塑造的。
• 🧬 我们的意识体验，包括自我意识，深深植根于那些使我们保持生命的生物学机制中。
• 🌌 人类对意识的理解正在经历根本性的变革，这可能改变我们对自身和自然界关系的看法。

Q & A

麻醉剂如何影响意识？

麻醉剂通过填充大脑使人进入一种完全的无意识状态，这种状态下人会经历一种脱离和瓦解的感觉，随后可能会感到昏昏欲睡和迷失方向，但意识会重新出现。

意识是如何在大脑中产生的？

意识是由大脑中数以亿计的神经元的联合活动产生的，这些神经元是微小的生物机器，共同作用生成了我们的意识体验。

为什么说意识是科学和哲学中最大的谜团之一？

意识的产生机制尚未完全明了，它是如何从大脑的物理过程中涌现出来的，这个问题至今仍然是科学和哲学研究的前沿课题。

演讲者为什么认为意识与智能是不同的？

演讲者认为意识与智能不同，因为意识更与我们作为活生生的有机体的本质有关，而智能则与纯粹的智力有关。

演讲者是如何描述大脑作为预测引擎的？

大脑被描述为一个预测引擎，它结合感官信号和对世界的先验预期或信念，来形成对外界事物的最佳猜测。

视觉错觉如何说明大脑的预测机制？

视觉错觉，如灰度错觉，展示了大脑如何使用其内置的预期来解释感官输入，即使在物理条件不变的情况下，我们的感知也会因为大脑的预测而改变。

橡胶手错觉实验是如何工作的？

在橡胶手错觉实验中，通过同时触摸隐藏的真实手和可见的假手，大脑会将假手误认为是身体的一部分，这说明了大脑如何基于感官一致性来预测身体边界。

为什么说我们的意识体验是一种控制的幻觉？

我们的意识体验是由大脑基于预测性感知机制生成的，这些机制是为了控制和调节我们的生理状态，以保持生存，因此我们的感知体验可以被视为一种控制的幻觉。

演讲者如何看待人工智能获得意识的可能性？

演讲者认为人工智能获得意识的可能性很小，因为意识与生物体的本质有关，而不仅仅是智能。

演讲者提出了哪些关于意识研究的科学策略？

演讲者提倡将意识的研究策略类比于生命科学研究，通过解释大脑和身体内部发生的事情来逐渐揭开意识的神秘面纱。

Outlines

00:00

💉 麻醉与意识的奥秘

演讲者分享了自己在麻醉下失去意识的经历，强调了从麻醉中醒来时对时间流逝的感知与正常睡眠后醒来时的不同。麻醉被描述为一种现代魔法，能够将人变成无意识的物体，然后希望他们能再次恢复意识。演讲者提出了意识如何产生的问题，指出意识是科学和哲学中最大的未解之谜之一。意识对于每个人来说意味着一切，没有意识就没有世界、自我或任何东西。演讲者还探讨了动物是否也有意识和自我意识，以及随着计算机变得更快更智能，未来它们是否可能发展出自我意识。演讲者认为，意识与生命和呼吸的生物本质有关，而不仅仅是纯粹的智能。

05:01

🧠 大脑作为预测引擎

演讲者介绍了大脑作为预测引擎的概念，解释了我们如何通过大脑的预测来感知世界。大脑通过结合感官信号和对世界的先验信念来形成对外部世界的最好猜测。演讲者通过视觉错觉的例子，展示了大脑如何使用先验期望来解释感官信息。他还通过声音错觉的例子，说明了大脑如何快速地使用新的预测来改变我们的意识体验。演讲者强调，我们不是被动地感知世界，而是积极地创造它。我们的体验更多地来自内部，而不是外部。

10:03

🤲 身体意识的幻觉

演讲者探讨了大脑如何产生身体意识，以及我们如何体验拥有身体的感觉。他通过橡胶手错觉实验来说明大脑如何通过视觉、触觉和位置的一致性来猜测身体的一部分。演讲者还讨论了我们如何从内部体验身体，以及这种内部体验与外部世界体验的不同。他指出，我们对内部状态的感知不是关于确定存在什么，而是关于控制和调节，以保持生理变量在生存所需的范围内。演讲者强调，我们作为有机体的基本体验，以及作为自我的体验，都深深植根于使我们保持生命的生物学机制中。

15:04

🌌 意识的多样性与未来

演讲者总结了意识研究的三个启示：我们可能会在预测机制出错时误认自己，这为精神病学和神经学提供了新的机会；我们作为生物的意识体验不能简化为或上传到机器人上的软件程序；我们的个体意识只是可能意识状态中的一个。演讲者强调，这些认识上的改变应该被庆祝，因为它们使我们更加理解自己，并意识到我们是自然的一部分，而不是与之分离。演讲者以对意识终结无所畏惧的观点结束了演讲。

Keywords

💡意识

意识是指个体对自身和周围环境的感知与认识。在视频中，意识被描述为一种由大脑中数以亿计的神经元活动产生的经验，是科学和哲学中尚未完全解开的谜团。意识是视频中的核心主题，因为它关系到我们如何体验世界和自我。例如，演讲者提到，意识的产生是大脑如何将我们变成对象，然后又变回人的过程。

💡麻醉

麻醉是指通过药物使人失去知觉的状态。在视频中，演讲者通过个人经历描述了麻醉状态下意识的丧失，强调了意识的脆弱性和对时间连续性的缺失。麻醉被用作一个例子来探讨意识的存在与消失。

💡预测引擎

预测引擎是指大脑如何根据以往的经验和当前的感官信号来预测外部世界的状态。视频中提到，大脑不是一个被动的接收器，而是一个主动的预测者，它不断地生成关于外部世界的最好猜测。例如，演讲者通过视觉错觉和声音错觉的例子来说明大脑如何根据预测来构建我们的感知体验。

💡幻觉

幻觉是指在没有相应外部刺激的情况下产生的感官体验。在视频中，演讲者提出我们所有的感知体验，包括自我感知，都是一种受控的幻觉。这意味着我们的大脑在没有外部输入的情况下也能生成体验，如在虚拟现实中的实验所示。

💡自我

自我是指个体对自己身份和存在的认知。视频中讨论了自我意识的不同方面，包括身体感知、第一人称视角的体验、意图和记忆。演讲者通过橡胶手错觉实验来说明大脑如何构建身体自我的体验，以及这些体验是如何依赖于大脑的预测机制。

💡内感受

内感受是指对内部身体状态的感知，如心跳、血压等。视频中强调了内感受在维持生命和调节身体状态中的重要性。演讲者提到，内感受与外部世界的感知不同，它更多地与控制和调节生理变量有关，而不是识别物体。

💡感知预测

感知预测是指大脑根据以往的经验和当前的感官输入来预测外部世界的状态。视频中，演讲者通过视觉错觉和声音错觉的例子来说明感知预测如何影响我们的感知体验，以及它是如何帮助我们理解意识的。

💡橡胶手错觉

橡胶手错觉是一种实验，其中一个人的真手被隐藏，而一个假的橡胶手被放置在他们面前。当两者同时被触摸时，人们会感觉到假手是他们身体的一部分。视频中，这个实验被用来说明大脑如何通过感官信号来预测和构建身体自我的体验。

💡虚拟现实

虚拟现实是一种通过计算机技术创建的模拟环境，用户可以与之互动。在视频中，演讲者提到了如何将虚拟现实与图像处理结合起来，以模拟过强的感知预测对体验的影响，从而探讨感知是如何被大脑的预测所塑造的。

💡生物学机制

生物学机制是指生物体内维持生命和功能的各种物理和化学过程。视频中，演讲者强调了意识和自我体验是如何深深植根于这些生物学机制中的，这些机制使我们能够生存并适应环境。例如，演讲者提到，我们的感知体验和自我体验都是由大脑的预测机制所塑造，这些机制是为了帮助我们生存而进化的。

Highlights

意识的神秘性：作者描述了在麻醉下失去意识的经历，强调了意识的神秘性。

意识的重要性：意识对于个体而言是一切，没有意识就没有世界、自我或任何东西。

意识与智能的区别：意识与智能是两个不同的概念，智能不一定需要意识。

意识的生物学基础：意识可能更多地与我们作为生物体的本质有关，而不仅仅是智能。

意识研究的进展：过去25年中，意识研究领域取得了显著的科学进展。

意识的科学探索：通过研究大脑和身体内部发生的事情来解释意识。

意识的属性：意识包括对周围世界的体验和自我意识。

大脑作为预测引擎：大脑通过预测来感知世界，而不是仅仅被动接收感官信号。

视觉错觉示例：通过视觉错觉说明大脑如何基于先验知识解释感官信号。

听觉预测与感知：听觉感知也可以通过预测机制来改变我们的意识体验。

虚拟现实与感知预测：通过虚拟现实技术模拟感知预测对体验的影响。

感知作为控制幻觉：我们的感知是一种受控的幻觉，由大脑的预测机制控制。

自我意识的幻觉：自我意识也是一种由大脑生成的控制幻觉。

橡胶手错觉实验：实验展示了大脑如何通过预测机制将假手误认为是身体的一部分。

内部感知与自我意识：我们对身体内部状态的感知对于维持生命至关重要。

意识与生存机制：我们的意识体验与维持生命的生物学机制紧密相关。

意识的预测性：我们通过预测机制将自己预测到存在中。

意识的多样性：人类意识只是可能意识状态中的一小部分。

意识的生物学意义：我们的意识体验是由生物学机制塑造的，这些机制与许多其他生物共享。

意识研究的未来：理解意识的生物学基础为精神病学和神经学提供了新的治疗机会。

意识与人工智能：仅仅使计算机更智能并不能使它们具有感知能力。

意识的哲学意义：意识研究挑战了我们对自我和自然的理解。

Transcripts

Just over a year ago,

for the third time in my life, I ceased to exist.

I was having a small operation, and my brain was filling with anesthetic.

I remember a sense of detachment and falling apart

and a coldness.

And then I was back, drowsy and disoriented,

but definitely there.

Now, when you wake from a deep sleep,

you might feel confused about the time or anxious about oversleeping,

but there's always a basic sense of time having passed,

of a continuity between then and now.

Coming round from anesthesia is very different.

I could have been under for five minutes, five hours,

five years or even 50 years.

I simply wasn't there.

It was total oblivion.

Anesthesia -- it's a modern kind of magic.

It turns people into objects,

and then, we hope, back again into people.

And in this process

is one of the greatest remaining mysteries in science and philosophy.

How does consciousness happen?

Somehow, within each of our brains,

the combined activity of many billions of neurons,

each one a tiny biological machine,

is generating a conscious experience.

And not just any conscious experience --

your conscious experience right here and right now.

How does this happen?

Answering this question is so important

because consciousness for each of us is all there is.

Without it there's no world,

there's no self,

there's nothing at all.

And when we suffer, we suffer consciously

whether it's through mental illness or pain.

And if we can experience joy and suffering,

what about other animals?

Might they be conscious, too?

Do they also have a sense of self?

And as computers get faster and smarter,

maybe there will come a point, maybe not too far away,

when my iPhone develops a sense of its own existence.

I actually think the prospects for a conscious AI are pretty remote.

And I think this because my research is telling me

that consciousness has less to do with pure intelligence

and more to do with our nature as living and breathing organisms.

Consciousness and intelligence are very different things.

You don't have to be smart to suffer, but you probably do have to be alive.

In the story I'm going to tell you,

our conscious experiences of the world around us,

and of ourselves within it,

are kinds of controlled hallucinations

that happen with, through and because of our living bodies.

Now, you might have heard that we know nothing

about how the brain and body give rise to consciousness.

Some people even say it's beyond the reach of science altogether.

But in fact,

the last 25 years have seen an explosion of scientific work in this area.

If you come to my lab at the University of Sussex,

you'll find scientists from all different disciplines

and sometimes even philosophers.

All of us together trying to understand how consciousness happens

and what happens when it goes wrong.

And the strategy is very simple.

I'd like you to think about consciousness

in the way that we've come to think about life.

At one time, people thought the property of being alive

could not be explained by physics and chemistry --

that life had to be more than just mechanism.

But people no longer think that.

As biologists got on with the job

of explaining the properties of living systems

in terms of physics and chemistry --

things like metabolism, reproduction, homeostasis --

the basic mystery of what life is started to fade away,

and people didn't propose any more magical solutions,

like a force of life or an élan vital.

So as with life, so with consciousness.

Once we start explaining its properties

in terms of things happening inside brains and bodies,

the apparently insoluble mystery of what consciousness is

should start to fade away.

At least that's the plan.

So let's get started.

What are the properties of consciousness?

What should a science of consciousness try to explain?

Well, for today I'd just like to think of consciousness in two different ways.

There are experiences of the world around us,

full of sights, sounds and smells,

there's multisensory, panoramic, 3D, fully immersive inner movie.

And then there's conscious self.

The specific experience of being you or being me.

The lead character in this inner movie,

and probably the aspect of consciousness we all cling to most tightly.

Let's start with experiences of the world around us,

and with the important idea of the brain as a prediction engine.

Imagine being a brain.

You're locked inside a bony skull,

trying to figure what's out there in the world.

There's no lights inside the skull. There's no sound either.

All you've got to go on is streams of electrical impulses

which are only indirectly related to things in the world,

whatever they may be.

So perception -- figuring out what's there --

has to be a process of informed guesswork

in which the brain combines these sensory signals

with its prior expectations or beliefs about the way the world is

to form its best guess of what caused those signals.

The brain doesn't hear sound or see light.

What we perceive is its best guess of what's out there in the world.

Let me give you a couple of examples of all this.

You might have seen this illusion before,

but I'd like you to think about it in a new way.

If you look at those two patches, A and B,

they should look to you to be very different shades of gray, right?

But they are in fact exactly the same shade.

And I can illustrate this.

If I put up a second version of the image here

and join the two patches with a gray-colored bar,

you can see there's no difference.

It's exactly the same shade of gray.

And if you still don't believe me,

I'll bring the bar across and join them up.

It's a single colored block of gray, there's no difference at all.

This isn't any kind of magic trick.

It's the same shade of gray,

but take it away again, and it looks different.

So what's happening here

is that the brain is using its prior expectations

built deeply into the circuits of the visual cortex

that a cast shadow dims the appearance of a surface,

so that we see B as lighter than it really is.

Here's one more example,

which shows just how quickly the brain can use new predictions

to change what we consciously experience.

Have a listen to this.

(Distorted voice)

Sounded strange, right?

Have a listen again and see if you can get anything.

(Distorted voice)

Still strange.

Now listen to this.

(Recording) Anil Seth: I think Brexit is a really terrible idea.

(Laughter)

Which I do.

So you heard some words there, right?

Now listen to the first sound again. I'm just going to replay it.

(Distorted voice)

Yeah? So you can now hear words there.

Once more for luck.

(Distorted voice)

OK, so what's going on here?

The remarkable thing is the sensory information coming into the brain

hasn't changed at all.

All that's changed is your brain's best guess

of the causes of that sensory information.

And that changes what you consciously hear.

All this puts the brain basis of perception

in a bit of a different light.

Instead of perception depending largely on signals coming into the brain

from the outside world,

it depends as much, if not more,

on perceptual predictions flowing in the opposite direction.

We don't just passively perceive the world,

we actively generate it.

The world we experience comes as much, if not more,

from the inside out

as from the outside in.

Let me give you one more example of perception

as this active, constructive process.

Here we've combined immersive virtual reality with image processing

to simulate the effects of overly strong perceptual predictions

on experience.

In this panoramic video, we've transformed the world --

which is in this case Sussex campus --

into a psychedelic playground.

We've processed the footage using an algorithm based on Google's Deep Dream

to simulate the effects of overly strong perceptual predictions.

In this case, to see dogs.

And you can see this is a very strange thing.

When perceptual predictions are too strong,

as they are here,

the result looks very much like the kinds of hallucinations

people might report in altered states,

or perhaps even in psychosis.

Now, think about this for a minute.

If hallucination is a kind of uncontrolled perception,

then perception right here and right now is also a kind of hallucination,

but a controlled hallucination

in which the brain's predictions are being reined in

by sensory information from the world.

In fact, we're all hallucinating all the time,

including right now.

It's just that when we agree about our hallucinations,

we call that reality.

(Laughter)

Now I'm going to tell you that your experience of being a self,

the specific experience of being you,

is also a controlled hallucination generated by the brain.

This seems a very strange idea, right?

Yes, visual illusions might deceive my eyes,

but how could I be deceived about what it means to be me?

For most of us,

the experience of being a person

is so familiar, so unified and so continuous

that it's difficult not to take it for granted.

But we shouldn't take it for granted.

There are in fact many different ways we experience being a self.

There's the experience of having a body

and of being a body.

There are experiences of perceiving the world

from a first person point of view.

There are experiences of intending to do things

and of being the cause of things that happen in the world.

And there are experiences

of being a continuous and distinctive person over time,

built from a rich set of memories and social interactions.

Many experiments show,

and psychiatrists and neurologists know very well,

that these different ways in which we experience being a self

can all come apart.

What this means is the basic background experience

of being a unified self is a rather fragile construction of the brain.

Another experience, which just like all others,

requires explanation.

So let's return to the bodily self.

How does the brain generate the experience of being a body

and of having a body?

Well, just the same principles apply.

The brain makes its best guess

about what is and what is not part of its body.

And there's a beautiful experiment in neuroscience to illustrate this.

And unlike most neuroscience experiments,

this is one you can do at home.

All you need is one of these.

(Laughter)

And a couple of paintbrushes.

In the rubber hand illusion,

a person's real hand is hidden from view,

and that fake rubber hand is placed in front of them.

Then both hands are simultaneously stroked with a paintbrush

while the person stares at the fake hand.

Now, for most people, after a while,

this leads to the very uncanny sensation

that the fake hand is in fact part of their body.

And the idea is that the congruence between seeing touch and feeling touch

on an object that looks like hand and is roughly where a hand should be,

is enough evidence for the brain to make its best guess

that the fake hand is in fact part of the body.

(Laughter)

So you can measure all kinds of clever things.

You can measure skin conductance and startle responses,

but there's no need.

It's clear the guy in blue has assimilated the fake hand.

This means that even experiences of what our body is

is a kind of best guessing --

a kind of controlled hallucination by the brain.

There's one more thing.

We don't just experience our bodies as objects in the world from the outside,

we also experience them from within.

We all experience the sense of being a body from the inside.

And sensory signals coming from the inside of the body

are continually telling the brain about the state of the internal organs,

how the heart is doing, what the blood pressure is like,

lots of things.

This kind of perception, which we call interoception,

is rather overlooked.

But it's critically important

because perception and regulation of the internal state of the body --

well, that's what keeps us alive.

Here's another version of the rubber hand illusion.

This is from our lab at Sussex.

And here, people see a virtual reality version of their hand,

which flashes red and back

either in time or out of time with their heartbeat.

And when it's flashing in time with their heartbeat,

people have a stronger sense that it's in fact part of their body.

So experiences of having a body are deeply grounded

in perceiving our bodies from within.

There's one last thing I want to draw your attention to,

which is that experiences of the body from the inside are very different

from experiences of the world around us.

When I look around me, the world seems full of objects --

tables, chairs, rubber hands,

people, you lot --

even my own body in the world,

I can perceive it as an object from the outside.

But my experiences of the body from within,

they're not like that at all.

I don't perceive my kidneys here,

my liver here,

my spleen ...

I don't know where my spleen is,

but it's somewhere.

I don't perceive my insides as objects.

In fact, I don't experience them much at all unless they go wrong.

And this is important, I think.

Perception of the internal state of the body

isn't about figuring out what's there,

it's about control and regulation --

keeping the physiological variables within the tight bounds

that are compatible with survival.

When the brain uses predictions to figure out what's there,

we perceive objects as the causes of sensations.

When the brain uses predictions to control and regulate things,

we experience how well or how badly that control is going.

So our most basic experiences of being a self,

of being an embodied organism,

are deeply grounded in the biological mechanisms that keep us alive.

And when we follow this idea all the way through,

we can start to see that all of our conscious experiences,

since they all depend on the same mechanisms of predictive perception,

all stem from this basic drive to stay alive.

We experience the world and ourselves

with, through and because of our living bodies.

Let me bring things together step-by-step.

What we consciously see depends

on the brain's best guess of what's out there.

Our experienced world comes from the inside out,

not just the outside in.

The rubber hand illusion shows that this applies to our experiences

of what is and what is not our body.

And these self-related predictions depend critically on sensory signals

coming from deep inside the body.

And finally,

experiences of being an embodied self are more about control and regulation

than figuring out what's there.

So our experiences of the world around us and ourselves within it --

well, they're kinds of controlled hallucinations

that have been shaped over millions of years of evolution

to keep us alive in worlds full of danger and opportunity.

We predict ourselves into existence.

Now, I leave you with three implications of all this.

First, just as we can misperceive the world,

we can misperceive ourselves

when the mechanisms of prediction go wrong.

Understanding this opens many new opportunities in psychiatry and neurology,

because we can finally get at the mechanisms

rather than just treating the symptoms

in conditions like depression and schizophrenia.

Second:

what it means to be me cannot be reduced to or uploaded to

a software program running on a robot,

however smart or sophisticated.

We are biological, flesh-and-blood animals

whose conscious experiences are shaped at all levels

by the biological mechanisms that keep us alive.

Just making computers smarter is not going to make them sentient.

Finally,

our own individual inner universe,

our way of being conscious,

is just one possible way of being conscious.

And even human consciousness generally --

it's just a tiny region in a vast space of possible consciousnesses.

Our individual self and worlds are unique to each of us,

but they're all grounded in biological mechanisms

shared with many other living creatures.

Now, these are fundamental changes

in how we understand ourselves,

but I think they should be celebrated,

because as so often in science, from Copernicus --

we're not at the center of the universe --

to Darwin --

we're related to all other creatures --

to the present day.

With a greater sense of understanding

comes a greater sense of wonder,

and a greater realization

that we are part of and not apart from the rest of nature.

And ...

when the end of consciousness comes,

there's nothing to be afraid of.

Nothing at all.

Thank you.

(Applause)