How to Build a Human: What Science Knows About Childhood

By Emma Byrne

'Byrne's book is about scientific parenting, and it is very welcome indeed ... breezy and digestible ... this is such a good book' Tom Whipple, The Times

Kids aren't all the same. You can't follow instructions and expect success every time. So what if parents approached their children as questions to be answered and not problems to be solved?

Scientist Emma Byrne takes evidence-based information on everything from physical and emotional development to what is really happening during sleep and separation anxiety, then shows how to apply it to the unique child in front of you. She challenges perceived wisdom by focusing on the variance as well as the mean - because your child is an individual, not an average.

Like all good scientists, you're going to have a few missteps along the way. You'll reach dead ends; you'll need to wrack your brain for new approaches. But by staying curious, creative and paying attention to what's really happening with your family, Emma Byrne will help you figure it out. Just in time for everything to change once again.

• Language: English
• Publisher: Souvenir Press
• Release date: Jul 1, 2021
• ISBN: 9781782836735

Emma Byrne

Emma Byrne is a graphic designer and artist. She is a graduate of Central Saint Martins School of Art and Design. She has won numerous awards for her design including The IDI (Irish Design Institute) Graduate Designer of the Year, the IDI Promotional Literature Award for her work on Brown Morning, and a Children’s Books Ireland Bisto Merit Award for her work on Something Beginning With P: New Poems from Irish Poets. She has illustrated many books, including Best-Loved Oscar Wilde, Best Loved Yeats, The Most Beautiful Letter in the World by Karl O’Neill, a special edition of Ulysses by James Joyce, and A Terrible Beauty by Mairéad Ashe Fitzgerald. She lives in a thatched house in Co. Wexford.

Book preview

1

Little Aliens

After 280 of Earth’s rotations safely travelling in their life support system, Nrobwen the Ybab left the mothership and took their first breath of Earth’s atmosphere. Never before had they experienced something so alien. There were wavelengths in the electromagnetic spectrum that Nrobwen had never experienced, exciting receptors in their sight organs, causing a cascade of fizzing, aimless activity in their cortex. There were vibrations in the atmosphere – the strangely thin atmosphere – that reached Nrobwen’s auditory sensor with more power and range than anything they’d ever felt before. And without the external support of their fluid-filled capsule, the air on this planet was viciously cold and Nrobwen’s movements were weak and ineffective. Earth seemed hostile; Nrobwen’s mothership had filtered the sights, sounds, and sensations of this entirely alien world. But now the mothership had closed behind them. The lone Ybab gulped in a lungful of the strange gas that surrounded them and started to wail.

Sorry. That all got a bit space operatic for a minute, didn’t it? But it’s the only way I can envisage just how fucking strange the world is for a newborn baby. According to UNICEF, around a third of a million Nrobwen Ybabs take their first breath of this planet’s atmosphere every day. And somehow we only spend a relatively small fraction of our lives screaming in abject terror. While our kids are perfectly capable of adapting to this strange new planet, for the first few years they’re incapable of surviving in it alone.

This is the trade-off: compared to frogs, chickens, turtles and sharks, mammals spend a long time growing potential members of our species. Vast amounts of energy go into the process of gestating our offspring: carrying them around internally, feeding them and processing their waste via the placenta. Even more energy goes into the milk-fed newborn stage, where our offspring, be they puppies or ponies, kids or cubs, are incapable of finding and digesting an adult diet. Typically, during this time, mammal infants are unable to sense or navigate the world in any meaningful way. In a period of time that lasts from a few hours to a few months, newborn mammals are utterly dependent on their caregivers. They need to learn to develop the ability to walk, to see, to hear. The longer it takes to learn to do these things, the more ‘altricial’ a species is. Turtles are ‘precocial’ – their offspring are literally born ready. Foals are fairly precocial: they can see, hear and move within minutes of their birth, though they’re reliant on milk for some months. Members of the cat family are on the more altricial end of the spectrum: functionally blind and deaf, and hardly able to crawl for the first few days and weeks. Humans are, in the main, one of the most altricial species – although we’re oddly precocious among the mammals when it comes to hearing. Wherever you are in that altricial–precocial spectrum, those first few months of life are spent trying to adapt to this entirely new environment.

Why do some species expend all this time and energy on altricial reproduction? Why do turtles and sharks get to lay-and-leave, while we humans have a couple of decades ahead of us, getting our kids ready to leave the nest?

There are two reasons for this. The first is adaptability. If your offspring enter the world with most of their behaviours fully developed, they’re ideally placed to cope in an environment that you, their parent, managed to survive in. However, if your offspring are born with senses and behaviours that develop in response to their experiences, well, as long as you can keep them alive for the first few months or years, they’ll develop in such a way that they can thrive in whatever environment you happen to have brought them into. Basically: the more developing your brain needs to do at the time you’re born, the more likely it is that you can spread out and occupy new niches.

There’s also a physical constraint on how much development human brains can undergo in utero. Among the mammalian order, we have freakishly narrow pelvises as a consequence of being able to walk on two legs. Babies’ heads have to fit through those pelvises. Something had to give, and evolution settled on leaving baby brains plenty of scope for growth, rather than killing labouring mothers – although it’s a pretty close-run race, which is why interventions like caesarean sections save thousands of maternal lives a year.

Evolution optimised thus: you want to walk on two legs so that you can see further? Better spend the first three months of your baby’s life watching them try to figure out what the fuck their hands are. I don’t know about you, but I’m happy with the trade-off, not least because tiny, flaily babies are hilarious.

This chapter is all about how children navigate a world through a mind that begins in a state of ‘blooming, buzzing confusion’¹ but that becomes a well-knit set of senses by the end of their first year, and that continues to develop through adolescence and beyond.

Making sense of Planet Earth

Before our children can start to get a sense of who they are, they need to get a sense of the world in which they live. To adults this might seem counterintuitive: surely we judge the world based on our sense of self? This is bigger than me, that is smaller. This is near to me, that is far. This smells good to me, this smells bad.

But, even up to adolescence, our children don’t experience the world in the way that we do. What might seem like cluelessness, clumsiness or confusion on their part is often simply down to the fact that children’s perception of the world – and of themselves in it – is still developing. It takes two decades or so to become an adult earthling: yet that is who we design the world around. As a result, in the first two decades of life, our children have a lot of work to do to develop their eyesight, their hearing and their sense of their own bodies. They also have to work out what is important in the constant stream of sensory data, long before they can figure out what’s going on and who they are.

That’s because the senses that we take most for granted are those senses that are the least developed at birth. Perceiving depth, understanding sounds, knowing where our bodies are and what they’re doing – these are all things that human infants need several months of experience in the world just to begin to learn. In contrast, the chemical senses of taste and smell have had a pretty thorough apprenticeship in the womb. We’ll look at these chemical senses in depth in the chapter on food and eating. This first chapter is about Nrobwen the Ybab’s most alien experiences: vision, hearing and the sense of self.

What are the senses? If you’re my sort of age you were probably taught that there are five senses: vision, hearing, touch, taste and smell, and that these contribute to what we know about the world in roughly descending order. You might even have an idea of the sensors that each of our senses rely upon, like ‘eyes are for seeing, ears are for hearing’, and so on. If you were lucky enough to have had a slightly more modern education, then proprioception – the sense of your body in space – might also have made the list.

However, life (and biology) are seldom that simple. Sensors have multiple functions. Ears don’t just contribute to hearing, they also tell us a great deal about posture and movement. Sight can overrule our sense of proprioception, making a rubber hand feel like it belongs to us, or making smaller objects feel heavier than larger ones of the same mass. Hearing contributes to vision: when presented with two flashes, but hearing three beeps, human volunteers will swear that they’ve seen three flashes.

That’s because perception is as much about what’s happening in our brains as it is about what reaches our eyeballs, earholes or skin. Perception relies on three things: sensors, salience and synthesis.

Sensors are the parts of our bodies that turn physical stimulus (vibration, electromagnetic excitation, movement) into the neural messages that our brains process. In hearing, for example, hairs in the inner ear vibrate, releasing ions that cause auditory nerves to fire. In our visual system, the rods and cones on the retina turn photons into neural messages. In addition, feedback from the muscles around our eyes contributes to depth perception: the extent to which your eyes start to cross when focusing on something gives you information about how close that object is.

Try it now if you can: switch between focusing on your finger in front of your face and looking at something far away. You’ll feel tension in the muscles around your eyes as you look at your finger, which releases when you look further away. Your brain uses that muscle strain to determine how large, close or fast an object is. Proprioception’s sensors are even more widespread and are found in the ears, the skin, our muscles and joints, and even in the early parts of the visual system.

But the sensors are only the first stage in processing data from the outside world. Our ‘sense’ of sight is a complex interplay between light falling on the retina, neural detectors for simple structures (lines, corners), important objects (faces, spiders), and important features (movement, contrast). We also confabulate – our brains make up missing data to fill in any gaps in the signal. For example, every time that your eyes make small jumps called saccades, which happen about three times a second, your brain discards the most recent information that it got from the retina, so that the world seems stable. We don’t experience life with a 3Hz flicker because our brains fill in the gaps for us. It’s this confabulation that also allows us to enjoy animated images from flipbooks to 3D films – we’re always running static pictures together in order to give the impression of movement. Our vision is nothing like a camera; it’s more like the cinematographer, director and editor of a feature film. In fact film editors exploit our saccadic filter; cuts in movies are made in such a way as to mimic the saccadic patterns of our eyes, which is why we’re comfortable watching scenes with many switches of viewpoint and angle, treating them as if they were a continuous view of the world.²

Beyond these sensors and early processors, our brains then apply further filtering for salience. Just like my inbox, there’s simply way too much data arriving from our sensors for our brains to process everything, so quite a lot of stuff gets filtered out. With our salience detectors, as with our spam filters, we’re usually spared from interruptions that aren’t helpful or relevant and can switch our focus to objects in the world that matter.

Our visual system decides whether the raw data looks like it might indicate a danger or a threat early on in the sequence of sensory processes: even before we can name the species we’ve been shown, pictures of snakes and spiders trigger human autonomic responses like faster heart rates and sweaty palms, while pictures of flowers or trees don’t. But occasionally we still manage to miss something truly remarkable. For example, in the famous ‘did you see the gorilla’ experiment, you can be attentively counting the passes between two basketball teams and – as a result of your intense focus – completely miss the person in a large gorilla suit who strolls through the court, stops to beat their chest at the camera, and strolls off. It’s not that your vision is faulty – this inattentional blindness filter keeps us focused on the task at hand while listening out for anything that might need our immediate attention.

The sense of hearing, too, has an internal mixing desk, deciding what signals are worthy of note. One of the most prevalent demonstrations of this is the so-called cocktail party effect where you suddenly hear your name mentioned by someone standing at the other side of the room during a noisy soirée.* The speaker didn’t say your name any louder than the rest of their chatter – in fact they probably said it even more quietly, given that they were talking about you behind your back – but your hearing flagged up that particular pattern of pressure waves for your attention because it matters to you; it’s salient. For years after we’re born, we continue to develop these salience filters until we make more sense of the world, doing so at the expense of noticing things that are unusual and unexpected. As the writer Will Storr puts it, ‘we see with our pasts’.³

But what about our children, with their pretty limited experience of the world? Research demonstrates that they do indeed struggle to switch their attention to things that we as adults assume to be salient. Like a request to pause a tablet or pick up a discarded shoe. It’s not that your kids are (necessarily) ignoring you on purpose: you’re just not very salient compared to almost every other thing in their world.

The younger your child, the harder you need to work to get them to pay attention to you. In preschoolers, the voice of a parent or teacher has to be at least 10 dB louder than background noise for a child to be able to follow what you’re saying, according to a study that is entitled, delightfully, ‘The cocktail party effect in infants’.⁴ Adult salience detectors are very narrowly tuned compared to those of our children, which allows us to hear things that are important but quiet. Children’s salience filters are wide open, which makes them very distractible by things that are bright, noisy or unexpected. Sometimes this is frustrating, but occasionally it is beautiful, as on a supermarket trip with our daughter when she was about eighteen months old. From her vantage point in the trolley, she pointed out everything that interested her. Distracted by the task of getting through the shopping list (and oriented solely to the shelves-that-might-have-the-things-I-need-and-for-goodness’-sakes-Tesco-stop-moving-them-please!) I was doing that kind of parental echoing that – as we’ll see in the language chapter – is a really important part of teaching language. ‘Storbees!’ ‘Yes, darling, yummy strawberries.’ ‘Oranges!’ ‘Yes, juicy oranges!’ ‘A elephant!’ ‘Yes, darling, a nice, big … what? Where?’ ‘A elephant in the bananas!’

There was indeed an abandoned toy elephant in the bananas. Without the attentional shackles of a shopping list, my eighteen-month-old’s attention could wander happily. I sometimes miss those days when everything from ‘windmills’ (wind turbines) to ‘pijishins’ (her first attempts at ‘pigeon’) and ‘bishisicles’ (bicycles) was worthy of note. As her spotlight of attention narrows she’s more capable of navigating the adult world, of helping us find the coffee and cornflakes, but I wonder if we’ll ever spot the rogue elephant in the bananas again.

Learning to see

Even at the tender age of three, our daughter’s filters had started tuning into the things that we had suggested were important, either by paying attention to those things or by rewarding her for noticing them. This is one of the particular advantages of altricial development that I mentioned earlier: our children develop filters that fit their environments, no matter whether they grow up in a forest, on a farm or in a flat.

The process of development that children go through makes them incredibly adaptable, but it’s surprising how much space in a newborn’s skull is already devoted to vision. A newborn’s eyeballs are already about two-thirds of the diameter they’ll be at adulthood, and their visual cortex is largely in place: that’s a large amount of precious skull real estate given over to vision. Don’t forget that the functional limit of the size of a newborn’s brain is the width of the human birth canal, so it’s not like evolution can just keep adding more space. So why is so much of that space given over to vision?

It may be because of the extremely early (at least compared to most other mammals) ability to fixate on faces. Despite having very little fine-grained vision at birth, human babies can track high-contrast patterns, and are particularly adept at focusing on faces within hours. But they don’t see the world in anything like the same way that we do. Human offspring are among the quickest to recognise our kin (within days if not hours of birth). Human infants may be so precocious when it comes to facial recognition because we’re so altricial in other ways – our dependence on our kin means that we need to recognise them early. But for all that precocity with regard to faces, human babies take proportionally far longer than other primates to develop the rest of their visual systems.

Take visual acuity: that’s the measure of how much fine-grained detail you can see. Your standard optician’s chart (the Snellen chart) isn’t testing your literacy. In fact there are several versions of the Snellen chart for non-readers that have pictures of boats, balls and bears. What the eye test is really measuring is how thick a set of lines must be before you can decipher what shapes they form. The higher your visual acuity, the more lines of the chart you can read, which equates to the thinner lines (also called a higher spatial frequency) that you can resolve.

Far from having a young-eyes advantage, the small letters on the optician’s chart don’t come fully into focus until at least the age at which children start school. In a review of over three decades’ worth of research, Professor Susan Leat and her colleagues at the University of Waterloo found that visual acuity doesn’t reach adult levels in humans until at least the age of five, and possibly as late as the early teens, depending on the methods used. For the first decade and a half of life, children need a lower spatial frequency (thicker lines) than do adults in their twenties and thirties. This isn’t just an eyeball thing: cortical processing of thinner lines takes time to develop. Up until the mid-teens, brain activity is still weaker than that of adults at higher spatial frequencies.⁵

What’s more, the world looks flat – or at least it doesn’t appear to have depth in the way that we understand it – for at least ten weeks after birth. Three-dimensional vision doesn’t emerge until around three months on average, and the variance in when it begins to develop is huge. In testing, babies showed no difference in brain activity when being shown the same picture to both eyes (a 2D image), or slightly different pictures to each eye (that would resolve to a 3D image in any organism that can perceive depth by using binocular cues). This indicates that, for the first three to four months of life, human babies simply don’t perceive