I don't think people are really mature at 18 years, and teenagers certainly are not mature, you may think this but you are not totally mature at those ages. The original 'question' of this discussion was what age children should be to realize that they come to a zoo to look at the animals and not to go to the playground. With some people, this is different (as in me), but I think that after the age of 10, you should (start) realizing that you are going to the zoo to look at animals and not top play at the playground.