When is too old to act childish? Or slightly immature?

7 Answer(s)

Under most laws, young people are recognized as adults at age 18. But emerging science about brain development suggests that most people don't reach full maturity until the age 25.

http://www.npr.org/templates/story/story...

The age limit depends on your income like so many other things.

you can always be a kid at heart and have fun, even at 20, 30.40,40,60,70 and 80/90!
but acting too immature is annoying, at 18 you are not a little kid and should not act like a child..but you can still have fun and be a kid at heart..

As long as you know your acting immature age doesnt matter. Just know when to stop.

New guidance for psychologists will acknowledge that adolescence now effectively runs up until the age of 25 for the purposes of treating young people.

http://www.bbc.com/news/magazine-2417319...

Never. Life is too short to be serious, but as an adult (I'm in my 50's) if I say say or do something that appears to childish or immature I just shrug it off, but I know when to stop and act my age and not my shoe size. So I do have a wise old head me sometimes.

The mid-20s or “25” is just an average age given as checkpoint for when the brain has likely become mature.

http://mentalhealthdaily.com/2015/02/18/...