<p>A child has hundreds of trillions of connections in the brain, twice as many as the adult. Experience determines which of these connections to take away and which of them to leave. This pruning process is what learning is, on a neurodevelopmental level. As the child grows into a adult, the brain becomes more and more complex.</p><p>As the baby grows into an adult, their processing rate also speeds up, from 4Hz at 4 months of age, 6Hz at 12 months of age, and finally 8Hz by 3 years of age. B the time the child reaches 10 (some say even 15) years of age, their alpha peak frequency (also called posterior dominant rhythm) has sped up to 10Hz, roughly, where it will stay until they reach their later 50s.</p>