There are some development markers which doctors take in order to check if some child is developing like "normal".
Some things only parents will be able to say.
Things like: It took a longer time to walk? To talk? (And so on). There are marks even about adolescents and adults. Can one focus in a task? Can one take care of his hygiene? and so on.
So, technically its is expected for all of us to decline (since we all know that people pretty old end up needing help to things like take bath, medicines, etc).
By checking those child markers one can be early diagnosed as Autistic which implies in in a different development with or without having a low intellectual quotient.
I personally have attention deficit between others issues related to autism. Never learned how to swim and have trouble with balance and spacial notion. This particular features in my case made playing sports a torture all my life. And so on….