Just a lighthearted theory I was thinking about:
I’ve often noticed that people seem to have a mental age that doesn’t necessarily correspond with their physical age. Some children have the personality of miniature adults whereas some adults forever seem like children. This could easily be explained away by saying some adults just never mature, but what about the children that seem so much older than they are, even when they’re raised by immature adults?
Perhaps there are some broad categories for mental age:
child: grabby and quick to upset but quick to heal.
teen: selfish/self-centered and turbulent.
young-adult: “knows everything” and doesn’t see the larger picture.
adult: practical, gets things done, and maintains order.
older person: understands more depth and sits back and observes.
In this theory, one’s overall behavior is still influenced by one’s actual physical age, but it’s regulated to some extent by the underlying mental age. For example, an “older person” that’s physically 16-years-old may still experience bouts of teen-like behavior, but it may be much milder. And when a “teen” reaches old age, perhaps they’ll have gained some insight on life but still fall back to extreme selfishness.
Also, a person may more likely feel “at home” within themselves when their mental age equals their physical age. For example, an “older person” as a child or teen may feel very out of place.
Again, this is just a lighthearted theory, sometimes it helps to shake some ideas loose by thinking of things in different ways.