For parents, carers and teachers, it’s often tempting to base our thinking on a child’s development around what we understand as “normal”. Much of the time we do this without thinking, describing a child as “doing well” in one subject and “behind” in another.
Whenever we make this sort of comparison, we have some sort of mental benchmark or yardstick in our head: for example, a toddler should be able to climb on furniture by age two. Increasingly, child development researchers are arguing that the same thing happens in child development research — the study of how behaviours and abilities such as language develop.
https://theconversation.com/why-theres-no-such-thing-as-normal-in-child-development-244681