This is just a test with 20 questions and at the end you are given your mental age. http://mymentalage.com/new I did it twice, the first time I was 8 years older than my age, the second time 11 years older. Whimper.
I'm 21 years younger mentally apparantly which is great as I love the company of younger people and doing lots of interesting things which a lot of people my age do not .