A second kind of brain change that occurs during childhood is called myelination, which refers to the coating of the axons of neurons with an insulating sheath of a fatty material, which makes transmission faster across the long-distance connections in those constellations of neurons. These slow processes of pruning and myelination are related to the great trade-off of human brain development: The young child’s brain has enormous potential (it can develop in many ways) but lower ability (it doesn’t do most things as well as an adult brain).
