i thought from the title that you might be asking if someone wasnt diagnosed, how could they know as an adult..
i was thinking if you have photographs from childhood, look into them. because the likelyhood of it showing up in photos is very high when you have autism. because your more in "your own world", and if you havent been diagnosed, then its likely that you lack the "early intervientions" that they do now.. and autism isnt just something that can be turned off during photographs and such when a small kid.

as for the actual question, i think the others are right. it depends on the individual and how it affects that person. we all physically age, but sometimes are stuck in a certain functional abilities level. i think if the individual is content in where they are and what is going on, then that could signal that they are a "normal" person... but in reality "normal" is in the eye of the beholder.. so... "normal" isnt really a set thing either, its indvidualized as well.

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