The Self Illusion

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The Most Wondrous Organ

One of the strangest experiences we can have is to hold a human brain in our hands for the first time. It surprises us for so many reasons, but for me, it was the realization that I could hold something that was once a person not so long ago. Our brain, and the mind it supports, is what makes us who we really are.

As a scientist, the brain has always fascinated me and yet it is not much to look at. When I first arrived at Bristol University, I used to organize a brain dissection class for my colleagues because, although we had all been taught that the brain plays the critical role in creating our mind, very few of us had ever had the opportunity to examine this wondrously mysterious organ. Some of us had measured the electrical activity of the brain as it goes about its business of thinking. Others had even worked with patients who had lost mental abilities through damaging their brains. But few had actually held another human’s brain.

So in December, just before we broke up for the Christmas holidays and after the medical students had finished their dissection classes, a group of about twenty fellow faculty members from the psychology department headed down to the medical school for a crash course in human brain anatomy. At the entrance to the dissection suite we giggled nervously like a bunch of first-year students as we tried on ill-fitting lab coats. White lab coats – now this was real science! However, that jovial mood suddenly changed when we entered the large, chilled dissection suite and were faced with the stark sight of human bodies in various stages of advanced deconstruction on the tables. This was not some fake alien autopsy, but involved real people who had lived real lives. The nervous mirth so boisterous outside the suite was stifled. The faces of our group turned ashen and pale with that tight expression that you often see at funerals as people try to appear dignified and composed when faced with death.

We split into groups and tentatively approached the lab benches, each of which had been furnished with a white plastic bucket. We put on rubber gloves and removed the lids. After the initial plume of formaldehyde fumes that stung our eyes and assaulted our nostrils had passed, we stared at the human brains inside each bucket.

At first sight, the human brain is rather unappealing. After it has been chemically prepared for dissection, it resembles a large split walnut with the rubbery consistency of a firm mushroom. Like a walnut, it is obviously shaped in two halves but beyond that, much of the structures are relatively indistinct. And yet we know that this small lump of tissue is somehow responsible for the most amazing experiences we can ever have in the universe – human thoughts and behaviours. How does this wondrous organ produce them?

The Matrix That Is Your Mind

In the science fiction classic, The Matrix, our hero, computer hacker ‘Neo’, played by Keanu Reeves, discovers that his reality is not real. He thinks he is living in the United States in the year 1999 but, in fact, he is living in a post-apocalyptic future world hundreds of years later where humans have been battling intelligent machines. His mundane daily reality is actually a computer program called the Matrix that is fed directly into his brain and the brains of other enslaved humans who are imprisoned in pods and harvested for their bioelectrical energy by the intelligent machines. But because all experience is so faithfully simulated, the humans are blissfully unaware of their true fate.

This plot may sound too fantastic to believe, but the movie is not that far off the mark when it comes to understanding the nature of the human mind. Of course, we are not enslaved humans controlled by machines, but there again, how would one ever know? These are entertaining suppositions, and all students of the mind should watch the movie, but one thing is clear: each of us really does have a matrix in our brain. This is because our brains are constructing simulations or stories to make sense of our experiences because as we have no direct contact with reality. This does not mean that the world does not really exist. It does exist but our brains have evolved to process only those aspects of the external world that are useful. We only sense what we are capable of detecting through our nervous system.

We process the outside world through our nervous system in order to create a model of reality in our brains. And just like The Matrix, not everything is what it seems. We all know the power of visual illusions to trick the mind into perceiving things incorrectly, but the most powerful illusion is the sense that we exist inside our heads as an integrated, coherent individual or self. As a self, we feel that we occupy our bodies. On an intellectual level, most of us understand that we need our brains, but few of us think that everything that makes us who we are can be reduced down to a lump of tissue. Most of us think that we are not simply our brain. In fact, we are our brains, but the brain itself is surprisingly dependent on the world it processes and, when it comes to generating the self, the role of others is paramount in shaping us.

Brain Reductionism

Some people get awfully upset with statements such as ‘we are our brains’ – as if this reduces or demeans the experience of life by making it material. Others point out that brains need bodies and so the two are inextricably linked. Still, others point out that brains exist in bodies that exist in environments and so it is illogical to reduce experience down to the brain. All of these objections are valid but ultimately we need to start taking a stand on how we think these all work together. The brain seems the most obvious place to start. We can change environments and replace most body parts, but our brain is pretty fundamental to who we are. And who we are includes a sense of self. That said, understanding where the sense of self comes from ultimately needs to involve the consideration of bodies and environments that shape the self.

Back in the dissection suite, it was the brain that had our full attention. This was no ordinary piece of the body. This was more than tissue. Somehow, each brain yielded the agony, the ecstasy, the confusion, the sadness, the curiosity, the disappointment and every other mental state that makes us human. Each brain harboured memories, creativity and, maybe, some madness. It is the brain that catches the ball, scores the goal, flirts with strangers or decides to invade Poland. Each brain that we held in our hands that afternoon in the dissection suite had experienced a lifetime of such thoughts, feelings and actions. Each brain had once been someone who had loved, someone who had told a joke, someone who had charmed, someone who had sex and ultimately someone who had contemplated their own death and decided they would donate their body to medical science when they were gone. Holding another’s brain in your hands for the first time is the closest to a spiritual experience I have ever had. It makes you feel humble and mortal at the same time.

Once you have overcome the emotional shock, you are then struck by the absolute wonder of this organ – especially if you have an appreciation of what an amazing thing the human brain is. Although you cannot see them with the naked eye, packed inside this lump of tissue are an estimated 170 billion cells.¹ There are many different types of cells but for our purposes, the nerve cell or ‘neuron’ is the basic building block of the circuits of the brain that do all the really clever stuff. There are an estimated eighty-six to one hundred billion of these neurons – the elements of the microcircuitry that create all of our mental life. There are three major types of neurons. Sensory neurons respond to information picked from the environment through our senses. Motor neurons relay information that controls our movement outputs. But it is the third class of neuron that makes up the majority – the interneurons, which connect the input and the output of the brain into an internal network where all the really clever stuff happens. It is this internal network that stores information and performs all the operations that we recognize as higher thought processes. By themselves, neurons are not particularly clever. When not active, they idle along occasionally discharging an electrical impulse like a Geiger counter that picks up background radiation. When they receive a combined jolt of incoming activity from other neurons, they burst into activity like a machine-gun, sending cascading impulses out to others. How can these two states of relative inactivity and a frenzy of firing create the processing power and intricacy of the human mind?

The answer is that if you have enough of them connected together, this collection of interconnected neurons can produce surprising complexity. Like the legions of soldier ants in a colony, or thousands of termites in one of those amazing earth mounds, complexity can emerge if you have enough simple elements communicating with each other. This was discovered in 1948 by Claude Shannon,² a mathematician working at Bell Laboratories in the United States on the problem of sending large amounts of data over the telephone. He proved that any pattern, no matter how complicated, could be broken down into a series of on and off states distributed across a network. Shannon’s ‘information theory’, as it became known, was not a dusty theoretical notion, but rather it was a practical application that revolutionized the communications industry and gave birth to the computer age. He showed that if you connect up a large number of simple switches that could be either ‘on’ or ‘off’, then you can create a binary code,³ which is the communication platform for all digital systems that control everything from an iPod to the orbiting International Space Station. This binary code is the foundation for every modern computer language. It is also the same principle operating in every living organism that has a nervous system.

The neurons communicate with each other by sending electrochemical signals through connecting fibres. A typical neuron has lots of fibres connecting with local neurons next to it but also has a long-distance fibre called an axon that connects with groups of neurons much further away. It’s like having a bunch of friends you talk to regularly in your neighbourhood but also a really good connection with a group of friends who live abroad. The neurons are jam-packed into a 3-4 mm thick layer on the outer surface of the brain, known as the cortex (from the Latin for ‘bark’). The cortex is of particular interest because most of the higher functions that make us so human appear to rely on what’s going in this tiny sliver of tissue. The cortex is also what gives the human brain its peculiar appearance of a giant walnut with many crevices.⁴ The human brain is 3,000 times larger than that of the mouse but our cortex is only three times thicker ⁵ because of the folding. Think about trying to cram a large kitchen sponge into a smaller bottle. You have to scrunch it up to make it fit. It’s the same with the human brain. Its folded structure is nature’s engineering solution to cram as much brain into a typical skull as possible without humans evolving heads the size of beach balls to accommodate the same cortical surface area. Ask any mother during delivery: she will probably tell you politely that it’s bad enough giving birth to a normal-sized head without it being any larger!

Like some strange alien creature extending tentacles, each neuron is simultaneously connected to up to thousands of other neurons. It is the combined activity of information coming in that determines whether a neuron is active or not. When the sum of this activity reaches a tipping point, the neuron fires, discharging a small chemical electrical signal setting off a chain reaction in its connections. In effect, each neuron is a bit like a microprocessor because it computes the combined activity of all the other neurons it is connected to. It’s a bit like spreading a rumour in a neighbourhood. Some of your neighbouring neurons are excitatory and like good friends, want to help spread the word. Other neurons are inhibitory and basically tell you to shut up. And every time the neuron has such a conversation with its different neighbours or long-distance pals, it remembers the message either to spread the word or be silent so that when the rumour comes round again, the neuron responds with more certainty. This is because the connections between the neurons have become strengthened with repeatedly firing together. In the words of the neurophysiologist Donald Hebb, who discovered this mechanism, synchronized neurons that ‘fire together, wire together’.

These spreading patterns of electrical activity are the language of mental life. They are our thoughts. Whether they are triggered from the outside environment or surface from the depths of our mental world, all thoughts are patterns of activation in the matrix that is our mind. When some event in the external world, such as hearing the sound of music, stimulates our senses, this stimulation is transmitted into a pattern of neuronal impulses that travels to relevant processing areas of the brain, which in turn generate a cascading pattern of activation throughout the brain. In the other direction, whenever we have an internal thought, such as remembering the sound of music, patterns of neural activity similarly cascade across the relevant centres of the brain, reconstructing the memories and thought processes related to this particular experience.

This is because the brain deals with distributed patterns. Imagine that the neural patterns in your brain are like domino patterns in one those amazing demonstrations where you topple one domino and trigger a chain reaction. Only, these dominoes can bounce back up again, waiting for the next time they are pushed over. Some dominoes are easily toppled, whereas others need lots of repeated pushes from multiple sources before they activate and set the pattern propagating.

Now imagine that, rather than there being just one pattern of dominoes, instead there are trillions of different patterns of dominoes overlapping and sharing some of the same excitatory and inhibitory neurons. Not all the dominoes topple because the inter-connectedness of certain clusters of neurons influences the path a neural activation takes. The fact that each neuron can participate in more than one pattern of activity means that the architecture of the brain is parallel. This is a really important point because it reveals a very crucial clue as to why the brain is so powerful. It can do several tasks simultaneously using the same neurons. It’s like the three-dimensional game of tic-tac-toe. Imagine the nought or the cross is like the active or inactive state of a neuron. It can start or stop a line that we will use as a metaphor for a chain of neural activation.

Those chains can spread in many directions. If you place a cross in the bottom corner of the lower layer, it also activates the patterns on the middle and top layers simultaneously. If you only consider the layout on one level, you are likely to lose the game. Rather, to play the game well, you have to think of parallel activation on all levels at the same time. Likewise, activation of neurons produces parallel activation in other connected networks of patterns. That is just as well, because the speed at which neural impulses travel from one neuron to the next in real time has been calculated to be just too slow for the speed at which we know the brain can perform multiple operations. The best explanation for our efficient brain speed at completing tasks is this parallel organization of the neural patterns.⁶ Our brains really do multitask using the same hardware.

Figure 2: Parallel processing works like three-dimensional tic-tac-toe

With such an arrangement, consider how a lifetime of experiences could operate as a multitude of fingers that topple different dominoes, creating different patterns of activation. In this way, the full diversity of what happens to us during our lives could be stored in the complexity of the neural circuitry as distributed parallel patterns. With billions of neurons, each with up to 10,000 possible connections with neighbouring neurons, that arrangement has the potential to create an almost infinite number of different patterns of connectivity. The mathematics of brain connectivity is mind-boggling. For example, if you just took 500 neurons all connected together so that each neuron could either be in a state of on or off, the total number of different patterns is 2⁵⁰⁰, a number that exceeds the estimated total number of atoms in the observable universe.⁷ Given that there are billions of neurons, you can understand why the human brain is considered the most complicated structure known to man – or, to be more accurate, rather unknown to man.

So this is how the brain basically works. Just like Keanu Reeves’s Neo, you have no direct connection with reality. Everything you experience is processed into patterns of neural activity that form your mental life. You are living in your own Matrix. Wilder Penfield, the famous Canadian neurosurgeon who reported how he could induce dreamlike flashbacks in his conscious patients when he directly stimulated their cortex during operations, most dramatically demonstrated this. He wrote, ‘They were electrical activations of the sequential record of consciousness, a record that had been laid down during the patient’s earlier experience.’⁸ He even operated on his own sister and showed that direct stimulation of the cortex triggered motor actions, sensations and thoughts. It’s these patterns of connectivity that encode all the information we process, memories we store and plans that we intend execute. Love, hate, the capital of France, the winners of the last World Cup soccer tournament, how to pitch a tent, how to divide by ten, the plot of your next novel, the taste of chocolate and the smell of oranges – every feeling, bit of knowledge and experience you have or plan to have is possible because of the cascading activation of neurons. Everything we are, can do and will do is nothing more than this. Otherwise we would need ghosts in the brain and, so far, none have been found.

How the Developing Brain Gets Organized

Of course, the human brain is considerably more organized than a chaotic jumble of overlapping circuits. Many areas have been mapped that correspond to different tasks or functions that the brain undertakes. There are brain regions that process information as it arrives from the senses. There are brain regions that plan, initiate and control movements. There are brain regions where personal memories are stored. There are regions that perform calculations. There are centres for emotion, aggression, pleasure and arousal – the fire in the belly of the machine that gets us out of bed in the morning and motivates us to act on the world.

One way to consider how the brain is organized structurally and functionally is to consider it like an onion. At the core of the onion is the brain stem that regulates the basic body functions that keep us alive, such as breathing and blood circulation. Above the brain stem is the midbrain region that controls activity levels such as wakefulness and appetite. The midbrain also governs basic motor control and sensory processing. Arising out of the midbrain is the limbic system, a network that controls emotions and drives such as aggression and sex. This has been called the ‘reptilian brain’ because it controls the sorts of functions we share with lizards and snakes.⁹ These functions are simply triggered by the sight of a competitor or a potential mate – like a knee-jerk reaction. Deep in the history of our species, we behaved in this automatic way but eventually we evolved higher levels of brain machinery that enabled us to control these reptilian urges. Sitting on top of everything is the cortex, a thin layer on the surface of the brain packed with neurons that support higher-order processing for interpreting the world, generating knowledge and planning actions.

Figure 3: Illustration of structural and functional hierarchy of brain systems

One of the most surprising discoveries in recent years is that the cortex is not where the majority of neurons are found. Most neurons are densely packed into a specialized region in the base at the back of the brain known as cerebellum, which controls movement.¹⁰ Only about a fifth of neurons are found in the remaining areas of the cortex that we usually associate with higher level thinking. This is surprising as one would assume that the complex mental processes involving thought would benefit from having more processors. However, the power is not in the number of neurons but the amount of connections. Like many performance issues in life, it’s not how much you have, but what you do with it and who you know. Even though the cortex has fewer neurons that one might expect, it has much greater connectivity with more extensive and longer fibres that join together different, widely distributed populations. This is the secret to the power of the human cortex – communication. By integrating information from diverse areas, the brain can generate rich, multidimensional experiences. Somehow, out of this richness comes our conscious self. Without cortical activity, you lose consciousness – you lose your self.

Not only does this multilayered model represent one of the major organizational layouts of the brain, but it also illustrates the relative developmental progression that has taken place in the brain through evolution, with the lower systems being more mature and operational than the upper systems which continue to develop into adulthood. Babies start out with functioning lower centres. With time and experience these lower regions become increasingly interconnected with the higher centres that exert influence and control so that the brain operates in a coordinated way.

You can see this coordination emerging throughout childhood. In fact, many scientists like myself believe that much of the change in early development can be attributed to not only the emergence of higher brain centres, but also the integration between these systems and their control over lower mechanisms. For example, something as simple as eye movement is controlled initially by lower brain systems below the cortex that are working from birth.¹¹ The problem is that these lower systems are fairly dumb. Those that control eye movement have evolved simply to direct your gaze to the darkest and brightest objects in the world. So for very young infants, the brightest things usually get their attention, but the trouble is that they lack the control to look away easily. For example, below two months of age, they have ‘sticky fixation’ – when they get stuck on a particular visually compelling target.¹² The trouble is that if the most visible thing always captures your gaze, then you are going to miss everything else in view. In fact, when I worked at a specialized unit for children with visual problems, we used to get young mothers coming in worried that their healthy babies were blind because they did not seem to move their eyes a lot. They seemed to be in some sort of trance, staring fixedly at the window. They wanted to know why their young baby didn’t look them straight in the eye.

The behaviour of these babies, like many of the limitations found in young infants, reflect the immaturity of their brains. During the early weeks babies have very little cortical control. Over time, cortical mechanisms start to exert increasing control over the lower mechanisms through a process called inhibition that works like a vetoing system to shut down activity. Inhibition helps to reign in the lower centres to allow more flexibility. In the case of sticky fixation, the cortical mechanisms enable the baby to look away from highly visible targets, such as the bright light streaming in through the window, and direct their gaze to less obvious things in the world.

It turns out that most human functions require some degree of inhibitory control. Here’s a cruel trick to play on an eight-month-old baby who has developed the ability to reach out for toys. Show them a desirable, colourful toy that they really want but put it in a large clear plastic container. At first they will bash their tiny little hands against the clear surface as they reach for it. Even though they will keep bashing their hands against the transparent plastic, they find it hard to stop reaching straight for the toy.¹³ The sight of the toy is so compelling that they cannot inhibit their reaches. In fact, inhibiting our impulsive thoughts and behaviours is one of the main changes over the course of a lifetime that contributes to the development of the self. When these regulatory systems fail, then the integrity of the self is compromised.

It is as if our brain is a complex machine made up of many subdivisions that compete for control of the body – like a complex factory under the control of a senior manager who oversees production. It is this senior manager in our head office that we all experience as the self. You may be able to find your own senior manager by a bit of introspection – the process of focusing in on your mental state. Try this out. Find a quiet spot and close your eyes. Turn your attention to your self. Try to locate where that self is. With both hands, point with your index fingers to the sides of your head where you think your inner self is currently located. When both fingers are pointing to where you think you are having experience at this very moment in time inside your head, keep one finger pointing and with the other hand point to this same place from the front of your head so you can accurately triangulate the site of your consciousness. Now draw the imaginary lines to find the intersection where ‘X’ marks the spot.

You have just located your own ‘point zero’ – where the ‘you’ inside your head sits. Figure 4 is taken from a study to map out where people think their point zero is located.¹⁴ It reveals that when we become mindful of our inner state, for most of us, it seems like we exist inside our heads, somewhere behind our eyes. We believe that this is the place where we are listening to a running commentary of thought, experiencing the sensations that the world throws at us and somehow controlling the levers that work the action and motions of our bodies.

Take a further moment to experience your body in this quiet state. If you concentrate you can feel its inner workings. As you read these lines, can you feel the subtle movements of your tongue bobbing up and down inside your mouth? Now that your attention has been drawn towards it, can you feel the pressure of the chair you are sitting on pressing against your backside? We can be in touch with our bodies but we are more than just our bodies. We control our bodies like some skilled operator of a complex meat machine.

Figure 4: Plot of locations where individuals typically feel their ‘self’ is located (based on study by Ferrari et al., 2008. Copyright permission given)

This internal self is sometimes called the ‘homunculus’ and this little chap is a real troublemaker. The homunculus is a problem because you are left none the wiser about the location of the self. In fact, considering the homunculus reveals why the reality of the self is a problem. There can be no single individual inside your head for the simple reason that, if true, then this homunculus would require an inner self as well. You would need a ‘mini-me’ inside the ‘you’ that is inside your head. But if the ‘mini-me’ inside your head is a homunculus, then who is inside the head of mini-me and so on, and so on? This would become an infinite regression leading to no end. Like an endless series of Russian matryoshka dolls, one inside another, the homunculus simply restates the initial problem of where the self is located in the mind. This is what the philosopher Dan Dennett has called the illusion of the Cartesian Theatre after the famous French philosopher, René Descartes, who thought that each of us possess a mind that inhabits our bodies. Dennett described this like sitting in the audience inside our heads watching the world of experience unfold like a play on a stage. But who is inside the head of the person watching the play in the Cartesian Theatre? Proposing an inner self simply does not help in solving the problem of where we are inside our heads.

Are we like a factory made up of lots of autonomous little workers inside our heads carrying out all the various tasks and functions that humans can achieve? To some extent we are, in that many of the subdivisions can operate independently. But there is not a worker army of homunculi any more than there is a chief executive in charge. Rather, our minds are a multitude of different processes and decisions that are often in conflict with each other, which often can occur below our level consciousness. This is why we will need to abandon the notion of internal individuals, which is inadequate to explain the complexity of our brain, and ultimately discard the notion that there is an inner self.

Mapping the Mind Machine

If the brain is a complex machine organized into different processing subdivisions, where does this organization come from? Who sets up all the domino patterns in the first place? This question is one of the major battlegrounds in neuroscience. To what extent are we preconfigured for the world by our genes and to what extent does that configuration emerge through our interaction with the world? It’s the old ‘nature versus nurture’ issue but at the basic biological level. It all depends on what aspect of being human you are considering but even the simplest features appear to combine biology with experience.

It is quite clear that we are born with many basic neural patterns in place. Many sensory and motor areas are well specified at birth even though they have yet to reach their full adult potential.¹⁵ But babies are not just passive sponges soaking up sensation from their environment – they can also act upon the world. For example, each human newborn is equipped with a repertoire of behaviours known as reflexes that play some vital role in development. Consider the rooting reflex, triggered by gently stroking the cheek of a newborn, which makes the baby turn their head and pucker up their lips in anticipation of a tasty nipple. If a nipple (or at least something of a similar shape) is touched to the baby’s lips, this then triggers a sucking reflex. You might think that the baby has decided to feed, but the truth is that these behaviours are completely involuntary and automatic and do not require any thinking. In fact, you do not need a very sophisticated brain to execute them. Anencephalic babies, born without any cortex, can still execute sucking reflexes because these behaviours are supported by primitive neural circuitry that lies beneath the cortex. But anencephalic babies are never destined to experience what it is to be human. They do not learn. They do not get bored.¹⁶ They simply respond. They will never develop a sense of their own self. Most die within days.

In contrast to the unfortunate babies born with brain damage, healthy infants are equipped with a brain that is designed to learn about its environment and this learning starts very early. We now know that the unborn baby can learn the sound of their mother’s voice, develop a preference for the food she eats while pregnant and even remember the theme tune to the TV soap operas she watches while waiting for the big day to arrive.¹⁷ All of this proves that the brain is already functioning and storing patterns of connections that represent the outside world. This is one reason why separating the relative influence of nature from nurture is always going to be hard and contentious. When do you start measuring? From conception or from birth?

Neuroscientists argue about how much of the adult brain structure is already evident in the infant, but it is quite clear that even if much of the blueprint for brain architecture has been passed on in the genetic code we inherit, there is still considerable scope for making amendments and building extensions to the original plan. This is where the environment shapes the brain by sculpting the matrix of neuronal connectivity that generates our minds.

Plastic Brains

I once bought a ‘Grow Your Own Brain’ gimmick toy, which was basically a compressed tiny plastic foam brain that you put in water, and it eventually expands to a much greater size. It’s amusing but not really a useful teaching aid. It is true that as babies grow their brains expand, but they are not simply swelling. The human newborn baby’s brain weighs about a quarter of the weight of an adult brain but within the first year more than half of the difference in weight is made up. What may surprise you is that this weight change is not because the brain is growing more neurons. In fact, newborn babies have almost their full complement of neurons that will remain with them throughout the rest of their lives. Rather most of that weight change is due the rapid expansion of communications between the neurons.¹⁸

As you can see in Figure 5, a diagram of the cortex taken from newborns through to fifteen months old, the human brain undergoes a massive explosion in connectivity between neurons during infancy.¹⁹ For example, during peak activity, the rat pup brain is generating neuronal connections at the rate of 250,000 every second. That’s fifteen million connections every minute. We do not know how fast the process occurs in humans. If anything it may well be even faster.

Figure 5: Illustration of neurons’ increasing connectivity during development

These structural changes reflect the way that biological processes interact with the world to shape the brain to fit into its environment. Two complementary processes create this sculpting.²⁰ First, genetic commands tell the neurons to start growing more and more connections. This creates an initial over-production of connectivity between the neurons. That’s why the diagram looks like the underground root system of weeds growing in your garden. Second, this bout of over-production is then followed by a period of pruning, where connections are lost between neurons.²¹ Around four out of every ten connections are lost with about 100,000 lost every second during the peak rate. This loss of connectivity is particularly interesting and at first surprising. Why would nature put in all the effort to build bridges between neurons only to knock them down almost equally as fast at a later date?

It turns out that the over-production and subsequent cull of connections may be a cunning strategy to shape the brain to its environment. A massive connectivity means that the brain is wired up for every potential pattern of activation that it may encounter from experience. But remember, only neurons that fire together, wire together. When neurons are not reciprocally activated, nature prunes their connections through inactivity. Returning to the metaphor of our extended neighbourhood, ‘If you don’t return my call, I am not going to bother contacting you later.’ Or for those of you familiar with social networking such as Facebook or Twitter, then it’s the case of ‘un-following’ followers who do not follow you back.

Reciprocal communication enables experience to change the brain’s architecture. We know this from animal research in which the effects of early environments have been shown to influence the connectivity of the brain. For example, if you raise rat pups in isolation without much to see or do, their brains are lighter and have few cortical connections compared to the brains of pups raised in an enriched environment where there are lots of other rats with which to play. Nobel Prize winners David Hubel and Torsten Wiesel found that the activity of cortical neurons in the visual area was impaired in cats and monkeys raised in deprived visual environments during early development. Moreover, specific types of visual deprivation produced selective impairments. For example, animals raised in a stroboscopic world had relatively normal vision for objects but could not see smooth movement in the same way that you cannot see continuous motion in a bad 1970s disco when the strobe light is on. One unfortunate woman who acquired damage to this part of her visual brain late in life described how difficult it was for her to cross the road because she could not judge the speed of approaching cars. When she poured a cup of tea, it looked like a series of snapshots of still photographs with the cup empty, half-full and then overflowing.²²

Sometimes the ability to see certain patterns is lost. Animals raised in environments without straight lines end up not being able to see straight. In short, early deprivation studies reveal that the punishment fits the crime.²³ If you remove some experience during early development, it has long-term effects later in life. Children raised with faulty vision grow up with permanent visual loss known as amblyopia. Amblyopia is not a problem of the eyes but of the brain regions that produce vision. That’s why putting glasses on someone with amblyopia late in life makes no difference. It’s also why amblyopes cannot fully appreciate 3D movies because they have lost stereovision, which needs good input from both eyes early on in life. If you want to make a difference, you have to correct the problem when it first arises so that the developing connections in the brain are not permanently ruined.²⁴ This leads on to discussion of another fundamental principle of brain development – sensitive periods.

Windows of Opportunity

Timing is everything, be it golf, sex or comedy. This turns out to be true for many basic aspects of brain development when input from the environment is required. Our brains have evolved to be malleable through experience but some experiences are required and expected at certain times during our lifetime. As noted above, deprivation can lead to permanent problems in later life but it turns out that these effects are most pronounced at certain times. Once the connections have been pruned due to inactivity, it is increasingly difficult to re-establish communication between the relevant parts of the brain. The window of opportunity has slammed shut.

These episodes of time-limited brain development are sometimes called ‘critical periods’ because no amount of remedial exposure after the window of opportunity has passed can reinstate the lost function. In truth, ‘sensitive period’ is probably more accurate as the brain has a remarkable capacity to recover, although it is worth noting that sensitive periods apply only to some of our human abilities and not others. Natural selection has evolved brains to expect certain experiences at certain times in development.²⁵ Why would nature hedge her bets that way? Surely blank slates are the best solution for uncertain worlds.

The reason is quite simple: like any successful manufacturer, nature always seems optimized to cut the cost of production. Nature prefers to build machines that are tailored to work without being over-specialized. For example, there is no point building an all-purpose machine when some purposes are unlikely or redundant – that would be too costly. It is much better and more efficient to anticipate the most likely world rather than having the machine specified in advance. This is how evolution selects for the best fit. Those with systems that are not optimized for their environment are not as efficient and will eventually lose the race to reproduce. This explains why babies’ brains are pre-wired loosely to expect certain worlds they have not yet encountered and then become streamlined and matched to their own world through experience.

Although the modern world appears complex and confusing, the basic building blocks of how we see it are fairly predictable and unchanging from one generation to the next. Experience simply fine-tunes the system. However, if you remove the experience during the critical time when it is expected, then this creates permanent problems. One of the first demonstrations of critical period loss comes from the Nobel Prize-winning work of Konrad Lorenz who showed that newborn goslings would follow the first moving thing they saw – even if that happened to be an elderly Austrian bird expert.²⁶ The early films of Lorenz show this bearded gent walking around smoking his pipe, being loyally followed by a line of goslings. Their bird-brains were equipped with a built-in mechanism to imprint on, and follow, the first big moving thing, whatever or whoever that was. For many animals, nature has produced a similar strategy to get them up and running as fast possible and to follow the important others in their gang. In the case of geese (and many other birds), nature gambled that the first moving thing was usually Old Mother Goose so there was no need to be too discerning. Austrian ornithologists would do fine. However, if the goslings were raised so that they did not see any large moving thing at all for the first ten days, then they did not later imprint because the window of opportunity had passed. In their natural state with no one to follow, these goslings would have perished, as their mother moved on.

Humans are more complicated than birds and our period of growth and nurturing is the longest in the animal kingdom, so there is less pressure to adapt as quickly. Nevertheless, there does appear to be evidence that we too have windows of opportunity and are preconfigured to attend to certain information from the environment. For example, human language development is usually trumpeted as one of the best examples of a brain-based ability that is both uniquely human and biologically anchored. In The Language Instinct,²⁷ Steven Pinker points out that just about every child, irrespective of where they are raised, learns to speak a language almost effortlessly at roughly the same time, whereas their pet hamster raised in the same household does not. It doesn’t matter how much you talk to your pet, you won’t get them answering you back. The only sensible explanation for this is that the human brain is pre-programmed to learn a language, whereas pet hamsters’ brains are not. Any infant raised in any environment can learn the language to which they are exposed. This proves that there is a built-in, uniquely human capacity to learn language, which must be genetically encoded, but that the actual language acquired is determined by the environment.

The human baby’s remarkable ability effortlessly to acquire language is only one line of evidence for the biological basis of language. Have you ever noticed how difficult it is to learn a second language the older you get? For example, I do not seem to be readily able to learn a foreign language and it is not through lack of trying. Despite hours of effort with Linguaphone learning tapes, I am unable to break the British stereotype of only being able to speak English. This is because the plasticity in the neural circuits in my brain that support language learning has been progressively lost. Some of us do not have such a problem but it may be related to whether we were exposed to other languages at a young enough age. This is one of the reasons that foreign-language learning is much easier before the age of seven. For example, when Korean immigrants to the United States were tested on their ability to learn English, individuals had no problem if they arrived before they were seven. For older immigrants, it became increasingly hard for them to learn English, even though they attended night classes and were highly motivated to learn.²⁸ This indicates there are biological limits to learning languages.

For many, just hearing the difference between languages becomes hard. In a classic study, Canadian infant researcher Janet Werker demonstrated that all babies could hear the different sound structures that exist in spoken Inuit and English languages before the age of ten months. However, the longer they were immersed in their own language environment, the more difficult it was for them to hear differences in the structure of other languages.²⁹ As we age, we lose the ability to detect the subtle differences between spoken languages. The best explanation is that our brains are tuning into the experience from our environments and losing the ability to process experiences that we do not encounter. Our brains are becoming less plastic for language learning. This is why, for Japanese speakers, English words that have ‘l’ and ‘r’ sounds are often confused, which can lead to comical miscommunication. Pinker wrote about his visit to Japan where he described how the Japanese linguist Masaaki Yamanashi greeted him with a twinkle in his eye when he said, ‘In Japan, we have been very interested in Clinton’s erection.’ This was several years before the US President would face impeachment in 1998 due to the Monica Lewinsky scandal.

Windows of opportunity exist in language and, as we shall see, even extend into other human qualities. But before we look into this, we should exercise against caution in over-interpreting the research on brain plasticity and critical periods described so far. This is because the discovery of critical periods in many animals led to some extreme beliefs and practices about human plasticity, especially when it came to how we should raise our children and what was the best parental practice. During the 1990s, there was a general panic that we were raising children in impoverished environments. The fear was that if we did not expose our children to a stimulating early environment, especially during the first three years, they would end up brain damaged. Suddenly, there was a public appetite for infant brain training and every parent and grandparent felt compelled to buy brain-enhancing devices from jazzy mobiles to hang over the crib, videos and DVDs to stimulate the brain, tapes of Mozart to play to pregnant mothers³⁰ and every other kooky notion that was ‘proven by research’ to improve your child’s chances of getting into one of the Ivy League or Oxbridge universities. The marketers even had the audacity to name their various products Baby Einstein and Baby Bach. John Bruer, then director of the James S. McDonnell Foundation that supported much of the neuroscience research behind the original animal work, even wrote a book, The Myth of the First Three Years, to try to counter this hysteria based on the over-extrapolation of animal deprivation studies to human development.³¹

The truth is that deprivation has to be quite severe before permanent loss occurs because most daily environments are sufficiently complex to provide enough input for hungry young brains to process. Parents should not be conned into thinking that they can enhance a process that has taken millions of years to evolve. In fact, some products such as baby training DVDs to enhance language have been found actually to impair language development because parents were relying on the television rather than the richness of normal social interaction.³²

Concerned educators and shrewd companies have either naively or deliberately misinterpreted the extent to which brain plasticity operates during sensitive periods. More importantly, there is little evidence that we can improve upon Mother Nature to supersize the early learning environment for a better intellectual outcome. But such messages fall on deaf ears. When it comes to doing what’s best for their kids, most parents err on the side of caution and so I suspect that the baby-brain boosting industry will always flourish. If only they would understand that the human brain has not evolved to absorb information from technology, but rather to absorb information from other people – much more complicated and yet so familiar.

The Gossiping Brain

At around 1.5 kg, the human brain is thought to be around five to seven times larger than expected for a mammal of our body size, and it has an especially enlarged cerebral cortex.³³ If our brain had the same architecture as a rodent, it would weigh just 145 g and hold a meagre twelve billion neurons.³⁴ Why do humans have such big, complicated brains in the first place? After all, they are very expensive to run, and although they only account for 2 per cent of typical body weight, they use up 20 per cent of metabolic energy.³⁵ It has been estimated that a chess grandmaster can burn up to 6,000 to 7,000 calories simply by thinking and moving small pieces of wood around a board.³⁶ What could justify such a biologically expensive organ? An obvious answer is that we need big brains to reason. This is why we can play chess. After all, a big brain equals more intelligence. This may be true to some extent but evolutionary psychologist, Robin Dunbar, has been pushing a less obvious answer – one that has to do with being sociable. He makes the point that big brains are not simply useful for any problem such as chess, but rather seem to be specialized for dealing with problems that must arise out of large groups in which an individual needs to interact with others.³⁷

This is true for many species. For example, birds of species that flock together have comparatively larger brains than those that are more isolated. A change in brain size can even occur within the lifespan of an individual animal such as the locust. Locusts are normally solitary and avoid each other but become ‘gregarious’ when they enter the swarm phase of their life cycle. This swarm phase of the locust is triggered by the build up of locusts as their numbers multiply, threatening food supply, which is why they swarm to move en masse to a new location. As they rub against each other, this tactile stimulation sets off a trigger in their brain to start paying attention to each other. Amazingly, areas associated with learning and memory quickly enlarge by one third as they begin to swarm and become more tuned in to other locusts around them to become a devastating collective mass.³⁸

Larger brains facilitate social behaviour. The link between brain size and sociability is especially true for primates where the extent of the cortex predicts the social group size for the species even when you take body mass into consideration. For example, gorillas may be big primates but they are fairly solitary animals with small close-knit family units and so their cortex is comparatively smaller than that of chimpanzees, which are much more sociable and like to party.³⁹

If you are a member of a species that has evolved to coexist in groups, then you are faced with some challenging decisions about how to spread your genes. To make sure that you have enough resources for your self and any offspring, you need to get sneaky. This is particularly true of primates who engage in deception and coalition formation, otherwise known as Machiavellian intelligence,⁴⁰ after the medieval Italian scholar who wrote the rulebook about how to govern through cunning and strategy. Primates in highly social groups try to outsmart and outflank fellow competitors for both the attention of potential mates and the distribution of resources. They need the mental machinery to keep track of others and second-guess their intentions. To do that, they need big brains with large areas of cortex to keep track of all the potential complex behaviours and information that large groups generate. For example, consider the number of interactions that exist between a dozen friends. Not only do you have to keep track of every relationship between each pairing, but you also have to work out all the potential combinations between subgroups within the group.

Using analysis based on all the major primate groups, Dunbar has shown that the cortex to group-size ratio can be used to predict the optimum group size for humans. According to Dunbar’s calculations, humans should coexist best in groups of up to 150. Any larger and the demands on social skills exceed our best capacity. It is a radical claim, and still very contentious, but there does appear to be evidence to support the hypothesis, especially when one considers pre-industrial societies. Over the course of human civilization, technology and industrialization have changed the way that we form groups. But keep in mind that the post-agricultural age began around 10,000 years ago and, with it, human behaviour changed as our species shifted from roving hunter-gathers to sedentary subsistence farmers. When you consider only those remaining hunter-gather societies that did not adapt to agriculture, the analysis reveals that Dunbar’s ratio exists among traditional societies. Even early religious settlements in the United States, such as the Hutterites, seem to have been most successful when their communities contained no more than 150 individuals. When a Hutterite community grows larger than 150, a new breakaway community is formed. Finally, analysis of modern companies reveals that large workforces operate and are managed best when employees form subdivisions of around the magic 150 workers. When Malcolm Gladwell was researching Dunbar’s ratio for his bestseller, The Tipping Point, he reported that Gore-Tex, the company that manufactures the high-tech material found in many sporting clothes, expanded its operations by forming subdivisions of 150 workers each time there was a need to open a new division.⁴¹ Dunbar’s number is an intriguing idea, especially as technology develops to change the way humans interact and keep track of each other. However, what worked for earlier societies may still be operating today in the modern, socially networked world.

In line with the growing field of social cognitive neuroscience, Dunbar is correct in arguing that the human brain has evolved specialized capacity and processing capability dedicated towards social functions. We know this because why else would humans have evolved into the species that spends the longest proportion of their lives as children dependent on adults? The simple answer must be that as a species we have evolved a strategy to pass on as much information as possible from one generation to the next through our storytelling and instruction. Our ability to communicate means that our offspring can know more about the world they are to embark on by listening to and learning from others without having to rediscover everything for themselves. In short, our extended human childhood means that we do not have to reinvent the wheel with each generation.

Baby Bat Brains

Now that you know the basic architecture of the developing brain is one designed to learn from others, I expect you are wondering what it must be like to think like a baby. To answer that, let’s consider this problem from the perspective of what it must be like to be an animal.

The philosopher Thomas Nagel⁴² famously asked, ‘What is it like to be a bat?’ Most of us with vivid imaginations can contemplate being much smaller, having fur and even wings (who has not dreamed of being able to fly?), but we cannot really know what it is like to be a bat. A bat would not have the mind of a human, because its brain is different and so you cannot use your human mind to experience being a bat. As a bat, you would not be able to see in the way that humans do because your vision is so poor. You would have to rely on echolocation, which is why bats squeak when they fly as a way of mapping out the air space in front of them and identifying tasty insects to eat. A bat probably has more in common with a dolphin than a bird. The list of differences goes on, but the point is that you can never know what it would be like to be a bat for the simple reason that you have a human brain and a mind. The same applies to human babies.

The developmental psychologist John Flavell once said that he would trade all his degrees and honours to spend five minutes in the mind an infant – just to experience what it must be like to be a baby again.⁴³ That would probably be a waste of his academic accolades. Just think about it for a moment. How could you see inside the mind of another person let alone a baby? Human babies have human minds but those minds are very different to one that we could appreciate as adults. If you had an adult mind inside the body of a baby, it would not be the same as thinking and experiencing the world as an infant. You would have to abandon all the knowledge and reasoning that you have built up as an adult. You would have to think like a baby. So you would not have an adult’s mind thinking like a baby. You would be a baby. As much as we might try, we can never get a true sense of what it is to have the mind of an infant. Every parent falls for this trick. When we stare at our infants in their cribs, we try to second-guess what they are thinking. We try to imagine what it must be like to be them, but for all our wishful thinking, they might as well be a bat.

An infant’s mind may be very alien to us but it is one that will eventually become an adult mind. Nature has built into humans the capacity to learn and to learn very quickly from others. It is not only doting adults who focus their attention on their offspring; each baby is wired to pay attention to others. It’s how our species has evolved a remarkable ability to transfer knowledge from one generation to the next and no other animal on the planet can do this as well as humans. But do babies know who they are? Babies have conscious awareness but does a baby have a sense of self yet? We cannot know for certain but I suspect not. Beginning the process of creating the self illusion requires early social interactions.