From website of Center on the Developing Child

One of the most essential experiences in shaping the architecture of the developing brain is “serve and return” interaction between children and significant adults in their lives. Young children naturally reach out for interaction through babbling, facial expressions, and gestures, and adults respond with the same kind of vocalizing and gesturing back at them. This back-and-forth process is fundamental to the wiring of the brain, especially in the earliest years.

Video: https://developingchild.harvard.edu/resources/serve-return-interaction-shapes-brain-circuitry/