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Brain development from newborn to adult is surrounded by many assumptions, myths, and false models.

This is also a singularly fascinating area – space won’t allow here to dive into intriguing areas such as how brain cells, neurons, migrate through the developing brain, how babies begin their learning in the womb and many of the refined instincts and cognitive skills that babies are born with.

Brain development is important to learn about: it impacts how parents think about their children, how teachers and educators design schooling and learning programmes, and how society deals and manages with many of its conceptions and its challenges (such as socio-economic status).

You are born with all the brain cells you need – but not the connections you need

You will be happy to know that you are basically born with all the neurons you need. Neurogenesis, the formation of new brain cells, as it is called, is most active in the womb reaching a pace of 250’000 per minute in the middle of the second trimester. There is some continuing neurogenesis in the first few years of life, but you are basically born with all the brain cells you will ever need and use. Note that some neurogenesis can continue throughout life particularly in the hippocampus which is heavily involved in long-term memory formation and in navigation and spatial memories.

Your brain overgrows in the first few months of life

Though we are born with all the brain cells we will ever need, the brain has had little time, or stimulus to develop connections between these cells – growth can reach thousands of new synapses (connections) per second! Hence the first few months are defined by limited neurogenesis but massive synaptic growth. The growing of connections between brain cells. By 18 months the brain of a toddler is massively overconnected. At this stage incidentally, there are certain skills that these toddlers are vastly better than adults. One of these is facial recognition.

From this early peak of brain cell generation, and what is called aborration (growing like a tree), it is all downhill (kind of!). The brain then aims to consolidate its connections and neurons. Another process that is very active in the first few years of life is a process called myelination – this is the insulation of the connections between brain cells through the long reaching “arms”, the axons of neurons. This increases the efficiency and speed of electrical transmission between cells.

Myth: you brain grows in the first few years of life

From 18 months there is the first large scale pruning phase whereby neurons are cleared out and synapses are cut. Essentially the brain grows more connections than it needs and then the connections that are actively used are then strengthened and those that are not are cut away. This is a natural process and continues in diminished form throughout life. Those connections that we need are kept and strengthened – and when they are strengthened, we also see lower energy to use these networks i.e. the networks become more efficient. Though it sounds counter-intuitive shrinking your brain at this stage increase your skills because it allows our brain to devote more resources to specific skills and use less energy to accomplish these.

Myth: your brain stops growing after puberty

Development of children’s ability from this age on has traditionally been done through observation. For example, Piaget’s legendary stages of formation. Fortunately, we are now at the stage where we can also map these development stages, which are broadly true, to what is happening in the brain and also highlight some more information, and surprises.

Critical phases for brain growth are at about 

  • 18 months
  • 3 years
  • 8 years
  • Puberty
  • Mid-twenties when the prefrontal cortex, at the front of the brain and responsible for executive functioning including impulse control, finally matures.

What is more surprising is that babies are born with a set of cognitive skills that are far more refined than we previously thought. Many had previously thought that babies were born a blank slate and that our environment provided all the input we needed to develop the brain. This was the predominant theory in the 1950s-1970s driven by behaviourism. Recent research has shown that newborns have a surprisingly refined set of cognitive skills:

Myth: babies are born as blank slates:

This is nice video highlighting some of the below and the research side is here.

·      Instincts
There are multiple instincts and reflexes that babies are born with from suckling, to grasping, to walking. The strength of the grasp of newborn is impressive (and worryingly decreasing in modern society). But there are others such as immediate attraction to face like shapes, immediate recognition of positive and negative emotions – see below.

·      Social
Babies have inbuilt recognition of faces showing higher attention to abstract diagrams represent faces (e.g. smileys) to focusing attention on real faces. They also have refined prosocial features built in with babies as young as 3-months old showing preferences for prosocial (nice) behaviour. This also extends to concepts such as justice and fairness which includes punishment of anti-social individuals!

·      Linguistic
Newborns have already had exposure to what will normally become their mother tongue and show similar intonation patterns right from the outset. But irrespective of actual languages babies show strong understanding of intonation, turn taking, and conversational practices. Babbling with a baby has all the features of a real conversation but without explicit use or comprehension of words. It serves one underrated feature of language namely that of bonding with others.

·       Numerical concepts
Babies are born with numerical concepts such as large and small quantities – not only this but there are some instinctive statistical concepts (see below) also built in.

·      Statistical analysis and probabilities
We consider statistical analysis and probabilities as more advanced mathematics, but the brain is born with inbuilt statistical and probability reasoning capabilities. The decision to take an umbrella is based on probabilistic inference, local knowledge, and past experience. None of us would consider this a refined probabilistic reasoning – but this is precisely what this is. Babies have been shown to be able to infer probabilities e.g. in boxes with different numbers of coloured balls the chances of pulling out a ball of a certain colour – showing surprise when the colour and numbers of balls seems to contradict the statistical probability of picking a ball of that colour (e.g. picking three red ball in a row in a box with 90% blue balls).

·      Biases
Many of the above can be considered biases, cognitive reflexes, or instincts which help us navigate the world around us. These can also manifest is different ways. For example, the concept of racial bias and in-group bias has been measured extensively in toddlers and babies. Babies exhibit racial preferences but also preferences for in-groups which may be defined as a group of cuddly toys that prefer the same snacks as oneself.

·      Others
There are multiple other inbuilt concepts such as preferences for certain sounds the Kiki bobo effect (hard sounds suggest hardness and aggressiveness). Halo and horn effect, bad skin bias and multiple other sometimes banal, sometimes amusing but almost always significant and part of our unexplored worldviews.

Myth: focused learning early on improves cognitive skills

In some people’s desire to develop geniuses there have been a swathe of products flooding the market and functional toys to encourage toddlers to develop cognitive skills. These may be well intentioned, but more likely seek to profit from parents’ insecurities, but generally will fall short of what the brain needs to develop. For the brain to develop healthily a number of things need to happen.

  • Care and nurturing
  • Social contact
  • Exploration and simulation
  • Linguistic input and conversations

The simplest way to develop these are through:

  • Play – structured and unstructured
  • Self-directed exploration
  • Social contact

In short playing in the garden with friends is a much better way to develop cognitive skills than any structured learning at any age up to 8 – this still holds true after 8 but focus can then be put on “learning” certain competencies and skills.

Early exposure to certain skills and competencies such as language, musical instruments, physical activities, will help develop these skills and competencies – as long as you don’t make it stressful. So yes, learning to play a musical instrument is certainly recommended but drilling a toddler through hours of practice may cause more damage than benefits.

This also has implications for childcare:

  • Mixed age groups may be better than single age groups
  • Unstructured play may be better than “learning games”
  • Plenty of physical activity should be taking place
  • Exposure to different languages may be beneficial
  • Exposure to and use of music is beneficial
  • Imagination is to be encouraged

What is under appreciated?

Physical exercise and movement are critical to human development and brain development. This is just as important for adults – brain growth and growth factors in the brain and genetic expression are all strongly influenced by exercise and movement. Physical education should be a daily part of any school regime. Preferably heavily incorporated into the classroom itself – it is simply how the brain is designed to operate.

Lying shows advanced cognitive development

Fairness and generosity are things we tend to drum into children: “sharing is good”. Many parents will notice however, their toddlers may appear to be selfish little monsters. This is natural and nothing to be worried about. This video shows some interesting experiments on this. However, as we develop broader networks and an understanding of the world, we start to develop what is called “Theory of Mind” i.e. an understanding of how other people think. This is also part of meta cognition which has received a higher focus on teachers’ agendas in recent years. The first stage of this development is when children start to lie to influence what you think: this can be quite amusing (see here) – and many parents may worry about the amorality of their children. It is a sign of the developing brain. Interestingly teaching young children about theory of mind – i.e. meta cognitive development may appear to be a good thing and something many teachers would consider a positive contribution to society. However, when children learn about theory of mind, research has shown they immediately begin lying more. They are getting a grasp on how to manipulate, or attempt to, the world around them and their social environment.

Hence children will move from honesty, to lying, to controlled honesty (as in adults). They will also move from selfish to more generous and this becomes noticeable around about 8 – this will also be guided by cultural influences.

Cultural Influences

The brain develops a frame of reference of what is normal – this is guided by inbuilt instincts, competencies and principles not to mention character and personality. Nevertheless, a culture also provides the stimulus for a growing brain and hence a development of the concept of what is normal and what is acceptable behaviour and not. This can have interesting outputs. For example, in one famous cognitive study Japanese and American subject were asked to view and describe a picture of a landscape with a lion on it. When describing the picture to researchers, Americans focused on the lion saying it was picture of a lion, and Japanese focused on the landscape. Same picture and different interpretations.

Nature or nurture?

We consider the nature and nurture debate a little tired and all research show that it is an interplay between both. For example, brain growth, plasticity, is also genetically influenced meaning some people will have more plastic brains than others. But we all have plastic brains to a degree – even into old age. What is however clear is that for a brain to develop its full capacity it will need to be in their right environment. This reflects in studies that have shown children in impoverished environments improving IQ and cognitive ability when moved to enriched and caring environments.

There are also numerous socio-cultural aspects with research showing clearly that poverty cause undue stress and severe cognitive impairments – not to mention the primary function of the brain which is to form an operating model of the world. Who is my friend, who is my enemy, what strategies should I develop to get by in life? These are vastly different in different socio-economic backgrounds. Schooling, it should be noted, is based on a middle-class view of how the world should work. Schooling in poverty-stricken areas may provide a whole other set of challenges that may not be considered, be underestimated, and certainly not considered in curriculum design.


  • Babies are born with a set of refined instincts, biases and operating models
  • The first few months of life are defined by massive connection building
  • Around 18 months the brain is defined by cutting back connections and brain cells
  • Lying is the first sign of advanced cognitive development and the concept of theory of mind
  • Around 8 children develop broader concepts of fairness and generosity
  • There are key changes in puberty with massive functional reorganisation (some argue that exams at this stage is a bad idea)
  • Sleep patterns also change around puberty
  • The brain doesn’t fully finish developing until mid-twenties
  • Brain change is always possible to some degree
  • Socio-cultural influences will have strong effects on cognitive development

Critical things to do with babies to promote development of healthy functional brains

  • Caring and nurturing and stable environment in first few years of life are critical
  • Conversation with adults (even if just babbling) – it needs to be back and forth
  • Extensive social contact
  • Play of all sorts (social, creative, artistic)
  • Self-directed exploration
  • Physical activity
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