I don't know if split-brain studies are familiar. In short, some people had the connections between their lobes cut off to combat epilepsy. As a result they had

I don't know if split-brain studies are familiar. In short, some people had the connections between their lobes cut off to combat epilepsy. As a result they had two separate brains, and if, for example, a funny image was shown to their left eye, they began to laugh, but when prompted why they were laughing, they couldn't answer. My point is, it is conceivable that your friend has some odd wiring to the parts of his brain which process language. It'd be interesting to get him to an fMRI and see whether the language is processed somewhere completely different to normal people - why not even in the cerebellum.