Young children are highly distractible. When everything is new, “newness” or “novelty” is compelling. Distractibility has a purpose. It alerts the young mind to what is novel and possibly important. The young brain has to code everything important into memory, and until this coding has continued for some time, there is no yardstick to measure what is and is not “important.” One reason that adults seem less distractible than children is because to them, everything is “old” and predictable. If adults were suddenly transported to an alien planet, they would become as distractible as children.
From Why Our Children Can’t Read and What We Can Do About it, by Diane McGuinness, Ph.D.