Question

The brain achieves 90% of its adult weight by

• A. 10 years of age
• B. 2 years of age
• C. 5 years of age
• D. 8 years of age

Hint:

The rapid increase in brain weight during early childhood is why early nutrition and stimulation are critical for long-term cognitive development.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Brain development is a rapid process during early childhood, out pacing the growth of the rest of the body.

Step 2: Detailed Explanation:
While a newborn's brain is only about $25\%$ of its adult weight, it undergoes rapid growth during the first few years of life:
- By age 2, the brain has grown to approximately $75\%$ of its adult weight.
- By age 5, the brain has achieved nearly $90\%$ of its final adult weight.
This rapid growth is driven by myelination (the formation of protective sheaths around nerve fibers to speed up signal transmission) and synaptogenesis (the rapid formation of connections between neurons).
This rapid development explains why the early childhood years are a critical window for cognitive, emotional, and social development, as the brain's neural pathways are highly malleable during this stage.
Although the brain continues to develop and refine its connections through adolescence and into early adulthood (particularly in the prefrontal cortex), its physical mass and weight are mostly established by age

Step 3: Final Answer:
The brain reaches approximately 90% of its adult weight by 5 years of age.