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Early Brain Development in Children

Early Brain Development

Early childhood is a time of tremendous brain development. The young developing brain literally changes shape and size in response to everything encountered in the early years. New environments, life experiences, caretakers, and relationships can all affect the way complex brain circuits are wired. This network of synaptic connections will ultimately determine brain function and the development of behavior.

A smiling newborn baby.


  • A baby’s brain at birth has roughly 86 billion brain cells (neurons)​1​, almost all the neurons the human brain will ever have​2​.
  • Although a newborn has about the same number of neurons as an adult, it has only 25% of the adult size.
  • Infant’s neurons are connected by only roughly 50 trillion new neural connections, called synapses, whereas an adult brain has about 500 trillion of them​3​.
  • By age 3, the synaptic connections have grown to 1000 trillion.
  • 90% of brain development completes by the age of 5​4​.
  • During early adulthood, the synaptic density will be half of that of a toddler at age two.

Early Developmental Milestones

Here are some of the brain development stages:

  • Week 3 post-conception – neuron production begins in the fetal brain.
  • At birth – the auditory system matures​5​.
  • 5 weeks – learning and memory formation.
  • 9 months – large motor skills.
  • 1 year 3 months – speech.
  • 1.5 years – fine motor skills.

When Does the Brain Stop Developing

On average, the brain stops developing around age 25. Although an individual’s brain growth trajectory can vary slightly, most people’s healthy brain development is complete in their mid-20s.

The prefrontal cortex is the last brain region to develop.

However, it doesn’t mean the brain stops changing.

Forming and changing interconnections in our brains is an ongoing process that takes place throughout our lives. Neuroplasticity allows new connections to form. But as we age, they do so at a much slower rate.

The experience-dependent brain

One of the most prominent characteristics of child brain development is synaptic pruning.

The network of synapses grows rapidly during the first year and continues to do so during toddlerhood.

Life experience will activate certain neurons, create new brain connections and strengthen existing ones, called myelination.

Unused connections will eventually be eliminated during synaptic pruning in the brain​6​.

Synaptic pruning is the neuronal process in which unused neurons and synapses are eliminated to increase efficiency in neuronal transmissions. This process occurs between early childhood and puberty.

Because early childhood experiences can literally shape the brain, babies can adapt flexibly to any environment they’re born into​7​.

But that also means what parents do or don’t do during these formative years can have a profound impact on the child’s healthy development – mental health and physical health.

Critical Periods & Plasticity

Within early childhood, developmental timing is also important. There are windows of time when different areas of the brain become relatively more sensitive to experiences.

This period of childhood brain development is called a critical period or sensitive period.

During critical periods or sensitive periods, synaptic connections in certain brain regions are more plastic and malleable. Connections are formed or strengthened given the appropriate experiences. After the critical period has passed, the synapses become stabilized and less plastic​8​.

For example, language skills learning is much easier for young children. They can learn a non-native language and attain proficiency more easily before puberty. So the sensitive period for language development, especially second language, is from birth to before puberty.

Nature vs Nurture In Child Development

Besides influencing a child’s brain architecture, early life experiences have other lifelong effects on a child’s development.

A large amount of scientific evidence indicates that life experience can affect gene expression — how information in a gene is used (epigenetics) — in some cases by slowing or shutting the genes off, and in others by increasing their output​9​.

This is why identical twins are not carbon copies of each other.

Although their genes (DNA code) are identical, their epigenetic markers are different from birth and continue to diverge as they interact with the environment in distinctive ways.

Even more important, these epigenetic changes can be permanent and passed down from generation to generation.

In the age-old nature-versus-nurture debate, epigenetics offers a surprising middle ground.

Genes are profoundly important, but so are environmental factors.

The Early Years Matter

Childhood is a time of tremendous sensitivity, a time when everyday experiences, both positive and negative experiences, bestow lasting effects​10​.

Developmental outcomes can be seriously impacted if kids are deprived of basic social and emotional nurturing in this developmental process.

This is confirmed by various research.

Differences in socioeconomic status (SES) in the early years of a child can result in disparities in brain structure. Extreme poverty is associated with lower gray matter volume and academic achievement​11​.

Children who experienced early neglect tend to have lower cognitive abilities. Early neglect affects the organization of white matter in the prefrontal cortex affecting its cognitive function​12​. It also hinders emotional development affecting social behavior​13​.

Also See: Asynchronous Development Of A Gifted Child And Their Unique Needs

Parenting For Brain Development

Neuroplasticity and epigenesis are two major cornerstones in understanding a child’s neurological development in the early years of life.

While we don’t need to be perfect parents (and who can be?), good enough parenting can do a child tremendous good. Quality early experiences provide a strong foundation for a child’s healthy development.

Among the different types of parenting stylesauthoritative parenting is the best parenting style associated with the best outcomes.

On the other hand, authoritarian parenting is associated with adverse childhood experiences (ACE). Chronic stress experienced by children of authoritarian parents can lead to toxic stress and an overreactive stress response nervous system.

Early childhood education also plays an important role in a child’s cognitive development and growth. Finding good child care providers and choosing a quality preschool for your child can benefit their development in early childhood and in the long term.


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    Hair NL, Hanson JL, Wolfe BL, Pollak SD. Association of Child Poverty, Brain Development, and Academic Achievement. JAMA Pediatr. Published online September 1, 2015:822. doi:10.1001/jamapediatrics.2015.1475
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    Hanson JL, Adluru N, Chung MK, Alexander AL, Davidson RJ, Pollak SD. Early Neglect Is Associated With Alterations in White Matter Integrity and Cognitive Functioning. Child Dev. Published online March 10, 2013:1566-1578. doi:10.1111/cdev.12069
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    * All information on is for educational purposes only. Parenting For Brain does not provide medical advice. If you suspect medical problems or need professional advice, please consult a physician. *