In developmental psychology, the increase in brain size and weight during early childhood is primarily due to the increase in __________.

• A. the thickness of the skull
• B. myelination and the growth of dendrites
• C. the number of neurons
• D. the amount of cerebrospinal fluid

Answer: (B)

Verified step by step guidance

1. Understand that brain growth during early childhood is influenced by changes at the cellular and structural level rather than just the size of the skull or fluid volume.
2. Recall that neurons are the basic units of the brain, but the number of neurons is mostly established before birth, so postnatal brain growth is not primarily due to an increase in neuron number.
3. Focus on the processes of myelination, which is the formation of a fatty sheath around nerve fibers that speeds up neural communication, and dendritic growth, which involves the branching of neurons to form more connections.
4. Recognize that these processes increase the brain's volume and weight by enhancing connectivity and efficiency, rather than by increasing cerebrospinal fluid or skull thickness.
5. Conclude that the primary contributors to brain size and weight increase in early childhood are myelination and dendritic growth.