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Birth
they have 25% the size of an adult brain.
They already have the basic structure in place, including the cerebral cortex. during 0-6 months, there's going to be rapid synaptogenesis, basic motor control, sensory development, and initial social engagement -
first year
the brain dramatically increases in size. the brain would reach about 70% of its adult size. it is primarily driven by the formation of synapses, increase in glial cells and myelin. at 6-12 months, the mobility has increased like crawling and standing, improved visual and auditory processing, and able to have social interactions like responding to names and speaking gibberish -
Age 2
the brain reaches 80-90% of its adult size. it's largely due to the proliferation of synaptic connections and increased myelination of nerve fibers.
During the 12-24 months, they try to speak their language, walking, able to do early problem-solving skills, being self-aware and have emotional regulation.