Making up the Mind - A short presentation

Talk at the Cheltenham Science Festival, June 8th 2007

“How the Brain makes up the Mind”
(Sharing the platform with Professor Raymond Tallis & Lord Winston)

How can I know anything about the world around me?
Everything I do know has to come through my brain. But my brain is not a passive receiver. My Picture of the world is a model created by my brain.

Let me explain - I only know about the world around me because of signals from my eyes and ears. My brain uses these signals to discover what is happening in the world. And my brain uses the same procedure whether it is exploring the physical world of concrete objects or the mental world of subjective ideas.

But this is not how it seems to me. My brain creates two powerful illusions: one about my relationship with the physical world of objects and one about my relationship with the mental world of ideas.

Let’s first talk about my illusion about the physical world.

First of all, I am not aware of how crude the signals from my eyes and ears are. My brain hides this from me. When I look around this town hall I do not notice that every face is blurred except the one I am focusing on. I believe that I can see everything, but a gorilla could walk through the hall and, if my attention was distracted, I would not notice it even though I was looking straight at it.

My brain doesn’t just hide the crudeness of my senses from me. My brain also hides all the work it has to do to make a clear and meaningful picture from those crude senses. Scientists have been very much misled by this illusion.

When computers were first invented in the 1940s people thought that the first thing these electronic brains would be able to do would be to recognise objects. That was because recognising objects seems so easy for us. Playing chess, on the other hand, would be far too difficult. Today, 60 years later, computers can play chess better than humans, but are still very bad at recognising objects.

Perhaps using my eyes to recognise objects is especially difficult? After all, there is no direct contact between me and all the things on this table. I rely on the light that is reflected off them. It is different for my own body. Nerves run directly from my brain to all the parts of my body.

Even so my brain doesn’t automatically know where my arm is. It has to work it out from signals in the joints and muscles and skin. If I cover up Prof Tallis’ arm with a cloth and place a rubber arm next to his now invisible arm I can easily make him believe that the rubber arm is his arm. I do this by presenting conflicting sensory signals. He sees the rubber arm being stroked and he feels his real arm being stroked in exact synchrony. In a few moments the rubber arm becomes his arm, which he sees and feels.

If my arm had to amputated I would very likely develop a phantom arm. I would feel it occupying a particular position in space and I might even be able to move it. There is nothing abnormal about having a phantom arm. We all have phantom arms all the time. It’s just that, most of the time, the phantom arm coincides with our real arm. By my trick with the rubber arm I can move that phantom away from your real arm. And there are many laboratory experiments showing that what we are aware of when we make a movement is the phantom arm created by our brain not the real one. So what we experience is the phantom arm created by our brain, not the real arm.

In just the same way my vision of the world is a hallucination constrained by reality. The only thing I know about is the picture of the world created by my brain. I have no direct contact with the real world. So when you or I are looking at some scene, what we see is not the real world, but a model of that world created by our brain. But, of course, there is a real world out there and the amazing thing is that most of the time, probably 99% of the time, the picture of the world created by my brain corresponds very well with that reality.

How does my brain do this?

My brain does it by prediction.

How do we recognise an object, such as a moustache, when we see it? Light is reflected off the moustache, enters my eye creating a signal that my brain interprets as a moustache. It may feel that this is how it works, but my brain actually does it in almost exactly the opposite way.

My brain starts with a guess about what might be there, given that I am expecting to see Lord Winston. My brain expects a moustache and predicts the signals that light reflected off a moustache would send to my eyes. But my brain doesn’t just use vision. My brain uses all my senses. When I look at this moustache my brain automatically predicts what it would feel like if I stroked it.

Whenever my brain makes predictions, they may be wrong. And it is these prediction errors that are crucial for creating a model of the world that works.

My brain uses the errors in my predictions to constantly adjust its model of the world. When my predictions are correct, then my brain’s model of the world does not have to be adjusted. I have the right model. And when I say my brain has the right model, I simply mean it has a model that works. Perhaps the model is not a true account of the world. But all we need is a model that successfully predicts what is gong to happen next. If we can successfully predict what is going to happen next we will survive.

So my brain is not just a passive receiver of signals. My brain is predictive and creative. This is why, if something goes wrong with my brain, I don’t simply become blind and senseless. I start seeing things that aren’t there. But my brain hides its creativity from me and gives me the illusion that I just see the physical world out there without any effort at all.

And is this ability to make models of the physical world that enables my brain to handle the subjective world of ideas also. All my brain knows about is sensory signals. Descartes taught us that there is a crucial distinction between the physical and the mental. But my brain makes no distinction between the physical and the mental. It can use the signals from my senses to construct models of the mental world as well as the physical world.

But my brain creates another powerful illusion about the mental world of ideas

This is the opposite kind of illusion to the one about the physical world. You all have various idea and beliefs in your minds, but I cannot see or touch these ideas. There is no illusion of direct contact. Our brain creates the illusion that we have direct contact with the physical world, but at the same time it creates the illusion that we are utterly detached from the mental worlds of others. And so it seems that we each live in a private and lonely world. So why are we all here are at this wonderful festival trying to put ideas into each other’s minds?

My brain makes models of the ideas in people’s minds using crude signals, predictions and errors just as it does when making models of the physical world. These signals are the sound of speech, the sight of a mobile face and the movements of the body as it performs actions.

But there is a very special feature of these signals, which makes them different from signals about objects: Much of the time these signals are deliberate messages from one mind to another mind. These signals are meant to communicate.

Communication is all about sharing our models of the world. Here again it is our brains that enable us to share these models. And, here again, our brain hides most of this sharing from us. By measuring brain activity we can see this sharing in action. If I know that some one is in pain activity appears in my brain in the same regions as when I am myself in pain. This is empathy. We are sometimes aware of this empathy. We can’t help wincing if we see someone’s hand trapped by a slamming door.

But we are not aware of many other kinds of sharing. If I see someone else being touched on her face, there is activity in the bit of my brain that would be activated if my face was touched, But I am not aware of this. When I see some one moving, my brain’s movement areas are activated. The cells in the brain that have this property have been called mirror neurons because they mirror the activity we observe in others. But I am not aware of this mirror system becoming active.

This effect can spill over into action. I don’t just see the movement. I start to imitate it. When people interact they tend to imitate each other’s movements. If I deliberately imitate your movements, then you will feel more friendly towards me, and, indeed, you will feel more friendly towards the world in general. But you will not be aware of the imitation that is going on. If you do become aware of the imitation then the effect no longer works. You will find me creepy and manipulative.

Our ability to communicate with each other so easily depends upon this unconscious web of shared models and connections and constraints that joins us all together. But our brains hide these links from us. Because I am not aware of how enmeshed I am with the minds of others my brain can create the strong conscious feeling that I am an independent agent. I have the experience of having free will and being responsible for my actions. And I have exactly the same experience about other people. I experience them also as free agents with free will and responsibility. This experience that we are all responsible agents plays a crucial role in building a cooperative society in which people behave with altruism.

It may seem a strange idea that what we see is not the real world, but a model created by our brains. But without this ability to create such models from the crude signals provided by our senses, we would not be able to enter the world of other minds.

But is the experience of having free will another illusion created by my brain?

Of course not. There are all sorts of complex processes that are involved when we choose one course of action rather another. Many different factors must be taken into account when we make complex decisions. We need to make the best decisions.

But free will is not about the quality of the decision. To have free will we must also bne able to make bad decisions. Free will is about the feeling of being an agent, the feeling that we are responsible for our decisions.

This feeling is probably the most important experience created by our brains.

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