“What is the question that you asked as a child, and are still asking today?”

Dr. Humberto Maturana, the legendary Chilean biologist, asked me this when we met a few days ago in the leafy suburb of Providencia, in Santiago de Chile. Maturana is now 90 years old but is still sprightly and sharp as nails. After some thinking, I replied: “Who am I?”

I think this is a question we all ask ourselves at some point – probably beginning when we are still young. Some people find answers in religion, others in their roles in society or in their family, others in their passion for sport or some other activity, and still others put the question aside, at some point, as life presents them with other things to worry about. But questions like this never really go away.

What does it mean to be “me”? I want to give you a sense of how I’ve come to think about this from the perspective of a neuroscientist (someone who studies the brain), and what lessons we can all take from this “story of the self.” But we start not with the self itself. We start with the world around us.

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Open your eyes and a world appears. This is the most natural thing ever, no conscious effort required. Whenever we are awake, we have vivid experiences of being in a world full of things, things with colors and shapes, with textures, and perhaps with smells, too. When I opened my own eyes just now, I saw a table in front of me, with a computer and a few empty mugs of different colors. It seems as though my eyes, all my senses, are windows onto an external “real world” which contains all these objects – and that these objects really have the properties they seem to have. It seems-as-though the mug nearest to me is actually red, and is actually round.

But how things seem is quite often a poor guide to how they actually are. The cats and coffee cups and dogs and donuts that make up our conscious perceptions are better thought of as things the brain “makes up” in order to best account for the stream of sensory signals in which it is continually immersed. The world we perceive comes as much from the inside-out, as from the outside-in.

To see this, imagine being a brain. There you are, locked inside the bony vault of the skull, trying to figure out what’s out there in the world. There’s no light in the skull; there’s no sound either. It’s completely dark and it’s utterly silent. Your eyes and your ears just deliver streams of electrical signals to the brain. These signals don’t come with labels attached – “I’m from a cat! I’m from a coffee cup!” – they are just electrical signals, signals which do not themselves have any shape, color, or sound. Therefore, in order to figure out what’s out there in the world, the brain has to combine these ambiguous sensory signals with some prior “expectations” or “predictions” about the way the world is. And that’s what we perceive – the brain’s “best guess” of the causes of its sensory signals.

Here's a very simple example, a visual illusion called “Adelson’s checkerboard.” In the left-hand image, the patches A and B look like they are different shades of grey. But they are in fact exactly the same shade of grey. The image on the right proves this by joining up A and B with a rectangle that has a uniformly grey colour.

What’s happening here is that the brain is using its knowledge that things in shadow appear darker than they actually are, so we end up seeing B as lighter than it really is. This “knowledge” is not something you are aware that your brain has, but it certainly has it. This is what I mean by the brain having “predictions” or “expectations” that are needed to transform raw sensory signals into vivid conscious perceptions.

If we take this example and run with it, our common sense way of thinking about perception gets turned on its head. It’s natural to think that what we perceive depends on “reading out” sensory signals that come from the outside world. In fact, the world we perceive depends on the brain’s predictions – its “best guesses” – which are continually created and recreated by the complex circuitry inside your head. Sensory signals just keep these best guesses in check, so that what we perceive doesn’t deviate too far from what’s actually there. The reality that we experience – the way things seem – is not a direct reflection of what’s actually out there, it’s a clever construction by the brain, for the brain.

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Now, the next trick is to realize that this process also applies to the experience of “being you” – to the self. The brain, remember, just sends and receives electrical signals. It is almost as isolated from the body as it is from the outside world. So, perceptions of “what it is to be me” must also depend on combinations of sensory signals and brain-based predictions. Only this time, these sensory signals and predictions have to do with the “self” and not so much with the world outside. This turns our common sense view upside down once again. The “self” is not the thing that does the perceiving. The self itself is perception, another kind of brain-based “best guess,” though one of a very special kind.

When we think of the self this way, it becomes clear that there is no single thing that is “me.” Instead, the experience of being me is composed of a whole different range of self-related perceptions – from what is and what is not my body, to experiences of making choices and seeing the world from a particular point of view, to recalling memories and making plans for the future. Nowhere behind any of this is a fixed “self.” You are the sum of your self-related perceptions, nothing more and nothing less.

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This is how I’ve come to think about the question “who am I” – and it’s a picture that I find oddly reassuring. When we realize that “what-it-is-to-be-me” is just a special kind of perception, I think it makes it easier to deal with the anxieties and worries that may challenge us at various times in our lives. These emotions, too, are just perceptions, and while we shouldn’t ignore their causes, there’s also no need to identify ourselves with them, convinced that things will never change. Just as the world changes, we, too, are always changing. This is the nature of perception, and it is to be welcomed, not feared.

Having said all this, I’ve also learned to be very modest about the conclusions we scientists reach, whether from theories or from experiments. As much as I like the story I’ve told you, it’s surely only a step along the way to a full understanding of the self, and it may turn out to be completely wrong. Science too is a story, a story that corrects itself against the evidence of nature. Nobody will ever be completely “right,” and each one of us can only strive to be less wrong than those who came before us. The beauty of science is only rarely in the answers it provides; it’s usually in the journey of discovery along the way.

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Let me end by asking you about your life question – what is the question that you can always remember asking and which has not gone away? If you can hang on to this, and keep seeking answers to it in whatever way you can (science is not the only way!), then you’ll have kept alive one of the most wonderful things about being human: the ability to be curious.