And when should they be able to do this?
Dd (3 and a half) has a longish name, let's say "Elizabeth". Myself and nursery call her Elizabeth, but dad, grandparents, friends, all shorten it to "Beth"
If someone asks dd her name she says "Eff" if I ask her full name she'll say "Izzeff"
I didn't think too much of it until she had a hospital appointment the other day and was asked to confirm her name, she replied Eff, and they ended up triple checking her identity to make sure I'd brought the right bloody child! 😂