You'd be amazed by the amount of things your brain can learn.
While I don't sing, I always encourage people who sing in my bands not to memorize the lyrics, but "learn" them, put themselves in the character's shoes. I got the firm belief that if you feel what you sing, you don't have to memorize anything, it just flows through, the same with other instruments.
James appears to do this very very well, that's why I admire him, not many singers in the musical scene do that.