At what age do we acquire "common sense"? Two years? Five years? Twelve years?

I could easily be wrong about this but I think common sense is acquired by learning. Learning things from a teacher, a parent, a friend or learning things from our mistakes; we try a behavior and don't like the result so we learn to use a different behavior that gives us results we do like. If parents, teachers,... do not teach us or we continue to make mistakes again and again without learning we do not acquire common sense. Or something like that...

I am probably babbling off topic now so if this makes no sense... well sometimes I don't.