Final answer:
Childhood brain development primarily involves the increase in dendrites and synapses, leading to more complex and efficient neural networks.
Step-by-step explanation:
During childhood, growth and development of the brain primarily occurs by increasing the number of dendrites and synapses.
The brain does indeed increase in physical size to a certain extent early in childhood, reaching about 90 percent of its adult size by age six. However, the more significant changes in brain development during childhood involve the dramatic increase in the number of neural connections rather than just an increase in neuron numbers or size. This includes the creation of new synaptic connections and the growth of dendrites, which together facilitate the enhanced brain functionality that occurs with development, allowing for more complex cognitive abilities.
Although neurogenesis (the formation of neurons) continues into adulthood, this is not the primary mode of brain development during childhood. Instead, the focus is on synaptic plasticity and neural network complexity, which is characterized by a blooming period of rapid dendritic and synaptic growth, followed by a pruning process that refines the efficiency of the neural networks.