Are you optimistic or pessimistic? Glass half-full or half-empty? Do you look on the bright side or turn towards the dark? These are easy questions for most of us to answer, because our personality types are hard-wired into our brains. As pioneering psychologist and neuroscientist Elaine Fox has discovered, our outlook on life reflects our primal inclination to seek pleasure or avoid danger -- inclinations that, in many people, are healthily balanced...