Human Growth and Development / Unit 3 HGD 0319 worked example, 60 to 90 seconds
The Brain's First Two Years
The idea
The brain's first two years combine four processes. Neurogenesis, the formation of neurons, begins before birth, and a newborn arrives with an estimated one hundred billion. Synaptogenesis connects them at an extraordinary rate, to about fifteen thousand synapses per neuron by two. Synaptic pruning then removes the connections that are not used, a process that continues into adolescence. Myelination coats axons so signals travel faster, and it is fastest in these first two years, which is when white matter grows most.
In practice
A toddler's brain holding twice the synapses of an adult's, with the unused ones set to be pruned.
Where people slip
More connections is not better in itself. Pruning is part of normal development: the brain keeps the connections experience strengthens and discards the rest, which is one reason early experience matters. By two, the brain looks structurally like an adult's, but the prefrontal cortex, which supports planning, judgment and emotional regulation, keeps developing into early adulthood.
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