The Nurture Revolution

Chapter 1

A SEASON FOR NURTURE

Did you know that a baby’s brain needs to experience visual input from the eye in order to develop brain areas for sight? If a baby’s brain doesn’t receive visual input from the eye in the sensitive time of infancy, they develop lifelong visual impairments.¹ My first lesson in neuroscience is one I want all parents to know: Infancy, from birth to age three years, is a season to grow the brain through experience.

My career in neuroscience has taught me that this connection goes far beyond sight. The development of many systems in the brain are time-sensitive. For many systems in the brain, infancy is a special, once-in-a-lifetime time period to build health and resilience that will serve our babies for their entire lives. For the first three years of their lives, infants undergo a wildly sensitive season of development, during which their brains are quite literally built by sensory, motor, social, and emotional experience. The infant brain possesses tremendous neuroplasticity, meaning it has great flexibility and an immense capacity to be shaped by experience.² The other seasons of great neuroplasticity for the brain are adolescence, when we mature into adults; and matrescence and patrescence, when we mature into parents.

When it comes to mental health, infant neuroplasticity is most notable in the stress system, which is vital to mental health. The development of the stress system influences other parts of what I call the “emotional brain,” including neurotransmitter systems, gut health, cognitive systems, and even DNA. Mental health arises from complex interactions and interconnectivity in the emotional brain. Each part of the emotional brain is affected by experience in infancy—we help our babies’ brains grow through the kind of care we give them. When we are nurturing, we build health into the emotional brain at every level.

HOW YOUR BABY’S BRAIN GROWS

Your baby’s brain and mind become astoundingly more complex minute to minute, day to day, and week to week. The human brain is a physical organ made up of vast and interconnected neuron and glial cells. All brains—from newborn to adult—have about 160 billion brain cells.³ Babies are born with nearly all of their brain cells, but their brains are about 75 percent smaller than adult brains.⁴ The infant brain gets bigger in the first three years of life both by growing an incredible mass of connections between cells and by adding proteins to specialize cells.⁵ During this period, the infant brain makes up to one million connections per second, guided by both genetics and experience, nature and nurture.⁶ In a quick ten-minute meal, for example, your baby’s brain will make up to 600 million new connections—and in a day their brain will form up to eight trillion six hundred and forty billion connections! In figure 2 you can see that the cells in a newborn brain have very few connections among them and few specialized proteins. From birth to three years, brain cells grow dense connections, and they grow in complexity by adding proteins. This rapid development is astonishing to witness. When I watch a baby roll over for the first time or share a smile with someone, I imagine the beautiful new connections sparking in their brain like little microscopic fireworks.

The infant brain doubles in size in the first year of life. It goes from 25 percent of an adult size to 50 percent of an adult size. By age three the infant brain is about 80 percent the size of an adult brain. By age five it is 90 percent of an adult brain, but it takes up to age twenty-five for 100 percent of the adult brain to be formed.⁷ Take a look at figure 3 to appreciate how rapidly the size of the infant brain increases between one week to three months, one week to one year, one year to two years, and two years to three years. In the image, you’ll also see that after three to five years old, the brain grows, but not as dramatically as it does from birth to three years.

I want parents to understand this process so they can clearly understand the opportunity for great brain flexibility and great nurturing possibilities in the first three years of life, when the infant brain is connecting like wildfire.

Both connectivity and protein growth are significantly influenced by experience.⁸ This time of dense growth is the key to why the infant brain is unique. We only have access to this neuroplasticity in the first three years of life. Although the brain does maintain some plasticity as we age, so we can later build on the systems that were formed in infancy (this is the basis of most therapy), it’s nothing like the plasticity we have in infancy, where we’re quite literally building the foundation of the brain and the systems associated with it.⁹

In figure 2, the panels labeled “3+” represent the end of infancy. At the end of infancy, the period of rapid growth ends. The brain initiates new cell growth that works to keep and solidify the circuits that were used the most in the first three years. In the first “3+” panel, inhibitory brain cells and protective glue-like brain cells, known as the extracellular matrix, begin to grow, in order to keep the brain circuits that were most used in infancy. The growth of these cells signals the close of the season of special neuroplasticity in the infant brain. It is very hard—though not impossible, as you’ll see—to change brain connections once the protective cells grow. The final panel labeled “3+” represents pruning, a brain mechanism that eliminates connections that were not used repeatedly in infancy. At the same time, at the close of infancy, the mechanisms that specialize cells by adding proteins end for many systems, like stress and neurotransmitter systems.¹⁰

The special season of neuroplasticity or flexibility of the infant brain is one of humanity’s biggest gifts. It gives us the ability to adapt to our environment and customize our brains for the world we live in, so we can be better prepared to survive in it. Humans live on every continent, in nearly every habitat on Earth, because our infant brains can morph and adapt almost anywhere.

NURTURING EXPERIENCES GROW RESILIENT BRAINS

Because of the highly flexible nature of infant brains, this time represents our biggest opportunity to build health into the brain. This may feel overwhelming—don’t we already have more than enough pressure and responsibility, and too little support, in raising our children? Do we really need yet another approach to childrearing, as if our friend groups and social media feeds weren’t flooded with tons of advice for the best way to parent? I get it; I’m a parent, too. I want to reduce your anxiety, your confusion, and your to-do list. What I want to offer you is simpler and more straightforward. It’s incontrovertibly supported in neuroscience. The most powerful tool we have for building healthy brains in infancy is not perfection, or any strict rules or requirements, or any product you need to buy. It’s quite simply nurture. Nurture has the tremendous power to grow a baby’s brain by connecting and shaping resilient emotional brains that enjoy improved mental wellness. Inside the brain, nurture leads to resilient stress systems, resilient protein expression from DNA, and resilient emotional systems—all of which make up mental wellness.

During infancy, brain cells are called “excitatory,” meaning they easily send messages to one another to build connections and build cells. Neuroscientists call communication between brain cells “firing” because the connections are so fast. The most frequently used connections during infancy are the ones that stay in the brain. As mentioned, in the process of pruning, those unused or not often used connections are eliminated. A good example of this phenomenon is in the auditory system. At birth, infants’ brains can process and learn sounds from every language on the planet. If an infant is exposed to the sounds of languages with phonemes that are distinct from their native language, such as a Vietnamese infant hearing English-language sounds, their brain wires in those sounds so they can hear and produce them later in life. However, if babies don’t hear non-native phonemes in early life, they are literally unable to hear and produce those sounds as adults. A native English speaker can approximate Vietnamese-language sounds, but they won’t be able to hear or produce an identical phoneme unless they’ve been exposed to them in infancy. This is because after infancy the auditory system prunes its connections, and the unused ones are eliminated.¹¹

Pioneering neuroscientists Donald Hebb and Carla Shatz famously taught us, “Neurons that fire together wire together and those that don’t won’t.”¹² For infant brains, this means that whatever repeated consistent experiences we give them quite literally build their brain connections and brain proteins. We can help build their brains for health and wellness through consistent experiences of nurture. Think of nurture as the dense connections and proteins shown in the three-year-old panel of figure 2 or the immense brain growth shown in figure 3; it’s the preventive medicine that acts to shape the brain, the mind, and mental health for generations to come.¹³

If there were specific genes or proteins in the brain that could improve mental health, scientists could develop medications to target them and successfully treat those issues, but there are no simple answers here. Instead, it’s become clear that mental health arises from complicated circuits between billions of cells and trillions of connections, largely formed in infancy.¹⁴ Until we can untangle trillions of connections, the most effective “pill” we have to improve mental health is wiring the infant brain with nurture. It’s not by accident that most pharmaceuticals for mental health struggles come with the advice that they be used in conjunction with talk therapy and other healing modalities.¹⁵ This is to help the brain’s intricate connections rewire through the combination of increased neuroplasticity from medication and brain rewiring from healing experiences, because mental health is not an isolated function in our bodies. It’s largely due to how well our stress system functions, or how well our brain and nervous system respond to stress and then return to states of safety. But it’s also due to how our thinking brain and our emotional brain developed in infancy, to our DNA and to epigenetics (meaning genetic markers we inherit), to our neurotransmitters, and even to our gut health. Not one of these acts alone; all the parts are elegantly interconnected and together they make up mental health.

But while good mental health is a complex combination of all of the above, the beautiful gift of infancy is that nurture works in all of these areas to build resilient stress systems and emotional brains in our babies.

When infants grow up with reliably nurturing caregivers, their brains are bathed in what I call a nurture bath—the infant brain releases a cocktail of hormones and neurotransmitters beginning with oxytocin and followed by a cascade of dopamine, serotonin, endorphins, and GABA—which helps them develop resilient emotional brain circuitry.¹⁶ When their brains soak in this nurture bath, or oxytocin cascade, their emotional systems develop great capacities to handle stress, emotion, relationships, and conflict—to be resilient. When the emotional brain is resilient, the whole brain can then devote resources to exploration, curiosity, thinking, creativity, forming relationships, and playing. All of these activities build the brain in an enriching way, at every age. With resilient emotional brains, babies, children, adolescents, and adults can spend more time being reflective, social, cognitive, creative, attentive, and flexible—the states that bring us joy, empathy, connection, and meaning. Resilient emotional brains also create healthy states of safety in our body. This manifests as a relaxed heartbeat, relaxed muscles, low inflammation, healthy blood flow to our vital organs, regulated digestive and immune systems, slower aging of the body’s cells or telomeres, and high-quality restorative sleep. This safety state protects the body from illnesses like heart disease, cancer, and diabetes, as well as digestive problems and neurological disorders. Simultaneously, this safety state powerfully provides protection from anxiety and depression.

Many of us spend a lifetime in therapy or in meditation centers or yoga classes cultivating a resilient emotional brain. Over years and a lot of work (and money), we try to change our emotional brains from reactive into resilient so that we can better handle stress, emotions, and relationships, and so that we spend less time feeling anxious, depressed, lonely, and dependent on substances, and in better health. But our babies can skip this endeavor; we can build resilience in their emotional brains now to last a lifetime. Every time you lovingly hold your baby and look into their eyes, every time you guide your baby from stress to calm, and every time you lie down beside your sleeping baby, their brain releases a beautiful cascade of hormones and neurotransmitters that bathe their emotional brain in connections, proteins, and DNA for lifelong health. When you are a reliable source of nurture, your baby’s brain can come to rely on bathing in those nurturing hormones. This primarily helps them grow a resilient stress system, which is the foundation of a resilient emotional brain, health, and wellness. The downstream effects of this are myriad. As you’ll see in the following chapters, these nurturing hormones and neurotransmitters develop the stress system, which goes on to develop the entire emotional brain, including:

Nurture is truly an awesome gift we can give to our babies’ brains. It is the source of everything we wish for our babies, the seed that grows an authentic, stable self, a center that holds, as well as ease, confidence, self-worth, and wellness. Nurture is entangled in every meaningful part of life: the people we love and who love us, our relationships, feelings, emotions, mood, health, success, and confidence. Nurture grows the parts of ourselves that carry us through adversity, lift us up, and bring us true joy. It provides access to the states of consciousness we all need and want.

WHAT IS NURTURE?

When I say “nurture,” it is to express an intention: deliberate time spent in a physical and emotional relationship with your baby. You respect your baby. You listen to and trust their cues and communication. Your goal is to be a supportive, reliable, and safe person for your baby. You intend to meet your baby’s physical needs and to be aware of their emotions, acting as a source of calm and regulation when needed. It also means providing repair when you don’t get it right. We are never seeking perfection. Repair is a part of nurture; being able to say “I’m sorry” also builds your baby’s brain.

Your nurturing, attuned presence helps regulate your baby’s stress and emotions. Your touch provides their brains with a nourishing oxytocin cascade. Your eye contact stimulates their thinking brain, and your words help them understand emotions. Your hugs help support their sleep. In all these ways and more, your loving presence puts your baby’s brain and nervous system into a state where it is primarily bathed in hormones that favor the development of a robust emotional system, which favors the development of lifelong mental health.

Your baby needs you to be reliably present, but you’re not always going to read their cues accurately or be in a space to be a regulated and attuned presence for them. We absolutely cannot and will not always get it right 100 percent of the time; no relationship is in sync all the time. There will be times you aren’t paying attention, act impulsively, or react from anger, fear, or anxiety. When you don’t get it right, you can repair it by apologizing, just like you would in any relationship. You don’t have to be perfect, you just have to be in the relationship with your baby. Nurture transforms the brain when it happens in our relationship reliably—when our babies can rely on us to be nurturing or to repair when we are not.

Since parents and baby are part of nurture, the whole family is part of the support and change to create a nurture revolution. I’m not talking about self-sacrifice or forcing yourself to do things you find uncomfortable, miserable, or boring; there are as many ways to nurture as there are parents, and I’ll help you find your unique way with lots of practical suggestions in part 2. This is nuanced work. At the heart of all nurture is the intention to be present, attuned, and close. To be a source of calm. To say, with your presence, “I’m here. I see you. You are important to me. You’re safe.” In a low-nurture culture that erroneously tells us to separate, limit presence and teach independence; to let them cry it out, not to spoil, to make them “self-soothe,” your gentle presence is indeed a radical act.

Nurture Is Remembered

You may think that none of this will matter because babies don’t remember anything from their early years, and you certainly wouldn’t be alone in that thought. The idea that infants don’t remember anything, so experience in infancy doesn’t really matter, is a common misconception. I’ve heard this from even the most informed and open-minded baby specialists, such as neonatologists, pediatricians, lactation consultants, and pediatric therapists. It is time to unlearn myth number 1, Infants don’t remember anything, so experience in infancy doesn’t really matter. This belief stems from a lack of clarity around memory. Memory means that an event occurs to permanently change brain cells and brain function. There are many forms of memory, including explicit and implicit memories.¹⁸ We tend to focus only on explicit memory, which includes autobiographical memories of conscious events in our lives—the “what,” “where,” “when,” “who” memories. Within infancy, the brain does form autobiographical memories, so infants have memories of events while they are infants. However, as adults we experience infantile or childhood amnesia, in which years after infancy we are unable to recall events in infancy from zero to three years. This is thought to be due to a rapidly developing hippocampus in infancy.¹⁹ It is true that most people don’t seem to remember events that took place in infancy, like their first bite of food or their first step, because our long-term memories for events begin to form around age three to four years.

However, a sizable amount of memory from infancy is stored in the brain as implicit memory, and this makes up the unconscious mind.²⁰ The massive growth of the infant brain means that a ton of memories and critical brain areas are formed in babyhood. Lifelong memories are encoded into the structure of the stress and emotional systems, and on top of DNA by epigenetics, which are formed in infancy. In infancy the brain creates non-autobiographical implicit memories like sensory, motor, and emotional memory. So while babies may not remember discrete events from their infancy, they will remember how to eat, how to walk, and, importantly, their DNA, stress systems, and emotional systems will remember how the people they love made them feel.

I like to adapt a Maya Angelou quote to illustrate this point: “[Babies] will forget what you said, [babies] will forget what you did, but [babies] will never forget how you made them feel.” Babies do not forget how they were nurtured. We may have limited recollection of early life, but nurturing experiences change our DNA, stress systems, and emotional systems and stay in our brains. So in fact, the reality is that the infant brain has a huge capacity for memory. We can best support our babies when we understand how powerful this period of life truly is.

Your presence, relationship, communication, play, laughs, and responsiveness with your baby in their first three years are transformative to the brain they will have for the rest of their life. As I will remind you often, you do not need to be perfect. Any amount you nurture benefits your baby. And repair is always possible for those inevitable moments (or days, or periods) when anger, frustration, or busy schedules get the best of us; in fact, repair is an important aspect of nurture—it helps build resilience. Your baby needs you to be your wonderful imperfect self. They benefit when you have intentions to be nurturing, and they benefit when you offer repair when it’s needed.

Nurture Is Hard Work, and It Matters

This gift of flexibility in infancy also makes human babies extremely vulnerable. Human infants require the most parental care of any species on Earth. Nurture is hard work. The constant needs of infants can be overwhelming. I have certainly felt this way. On top of this, many of us did not have our own needs met as babies and children, and it is new territory to be in a responsive, secure relationship.

So when you feel challenged by nurture, this is why: You are doing something profound. You are doing tremendous work building a brain, the most complex thing in existence besides perhaps the universe. You are building countless brain cells and receptors in your baby’s brain with your brain. This is intense, deep work and something to truly be proud of and celebrate.

Part of nurture is taking advantage of the neuroplasticity in our new parenting brains and taking care of ourselves as parents. Nurturing a baby is not meant to be done by one person—we need our partners, family, friends, and professional caregivers to take part in our baby’s lifelong well-being. When one person is doing most of the baby care, we want this person to be supported and nurtured by others as well. There are two vital layers of support for a baby. The first layer is the mother or primary caregiver(s) who takes care of the baby, while the second layer consists of those who take care of the mother or primary caregiver(s). Both are necessary yet often the second layer is lacking.

I want you to know that your hard work of nurturing matters. It is everything to your baby. It is brain-shaping and life-changing. Your child will benefit from your parenting throughout babyhood, childhood, adolescence, adulthood, and maybe as a parent themselves one day. Even more powerfully, your nurture will benefit your potential grandchildren, great-grandchildren, and so on. Nurturing one baby profoundly nurtures the future. Psychologist Louis Cozolino writes, “We are not the survival of the fittest. We are the survival of the nurtured.”²¹ The future is survival of the nurtured.

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