Compared to other mammals, human infants are born prematurely. Whereas a calf can walk almost immediately at birth, it takes a baby at least 12 months to reach that stage. This is because much brain development is still yet to happen.

Importance of early years (conception to age 3)

  1. A child’s brain grows at its fastest rate during its earliest years, growing to 25% of its adult size by birth and to 80% by age 3. During this period, the brain is very sensitive to being affected by its external environment and interpersonal experiences. It is also very elastic, able to learn and un-learn information more easily that at any other point in life.
  2. During this period, synapses (connections) are added at a rate of over 1 million per second. Afterwards, they are pruned faster than they are added, leaving the adult brain with 50 to 60% of the synapses of a 3-year-old. Before age 3, many of these connections become hard-wired through repeat use, whereas under-used genes are switched off. As a result, a young child’s brain development reflects the world in which they are raised, from their behavioural patterns to their emotions, language capabilities and mental health.
  3. Beyond age 3, the speed at which the child’s brain develops slows down and this elasticity is replaced by a mindset that becomes increasingly set in its ways.
  4. Due to this, a child raised in a loving, nurturing environment which is free from persistent, “toxic” stress will develop as healthy a brain as is possible. In contrast, a child raised in an environment of abuse, neglect or household dysfunction will see their cognitive abilities severely impaired, more so than if the damage were to have occurred at any other time in their life.
  5. As such, this period carries both enormous opportunity and risk for the later life chances of each child.


Case study: The Dunedin (New Zealand) Study

Dunedin’s sons and daughters were never meant to be famous.

The initial idea was to do a minor study into child health and development between ages 1 and 3. But the researchers didn’t stop there. Those 1,037 babies born between April 1972 and March 1973 mostly returned to be studied again at 5, 7, 9, 11, 13, 15, 18, 21, 26, 32 and, most recently, at 38-years-old.

Their lives have been scrutinised in more than 1,200 reports. Yet despite calling them back every few years for another study, it only took one to strongly predict the path they’d take in life: the first one.

The research team were able to pinpoint a sub-section of the group that held more than its fair share of personal issues, while also causing a disproportionate number of costly problems for everyone else. What became clear is that the members of this minority also frequently overlapped with a “high cost” group identified at age 3 following a series of brain health tests. In short, their life could be predicted before it had barely begun, with child maltreatment a common indicator alongside poor IQ test scores, low self-control and coming from a deprived background.

Having shown that children’s psychology at such a young age can strongly influence the rest of their lives, the Dunedin study has provided some of the strongest evidence for why it’s so important to get those early years right. To put this into practice, the 70/30 Campaign has created an action plan for how to achieve this.