Age doesn't mean shit. Sure, to an extent age can damper comprehension. But by the age of 10 the mind can be developed to at least hold a decent conversation.
Maturity is based on experience.
Now technically if you were 50 years old, sheltered from the world, you could have the maturity of the average 5 year old. This is the case with most. Discrimination against age is everywhere. I used to hear comments all the time from stupid people claiming that I did not know anything, etc. because of my age. I don't think so.