I gave myself a mental age of 7, as i still think it is quite fascinating to set fire to bee's wings as they whizz up and down the window,and have recently installed a full size ping pong table in the kitchen. I don't realy think any stinkie can vliadly claim to have a mental age of muych more than about 12 anyway.
Mind you, jimi's mental age must be five as he is not in the least bit embarassed at wearing a rubbish hat that his mum obviously forces him to wear on cold days, despite all his mates laughing, and he gets lost on his way to obvious thing like massive big boats that can be seen 10 miles off