Ben Carson is a famous brain surgeon, but he has rather fanciful views (to put it nicely) about many other things.
In response to the controversy over his belief that Joseph built the pyramids to store grain, a friend on Facebook asked if this meant that a once intelligent man was losing his mind. I offered, respectfully, that surgeons are very well informed about one thing, but this is no guarantee that they are well informed, or even thoughtful, about anything else.
This prompted a respected brain scientist to offer a useful perspective:
Medical School and residencies (particularly the 6-7 years required for neurosurgery) are designed to build specific skill sets and a pretty focal knowledge base. They're generally the antithesis of the classic liberal arts arc. They don't encourage breadth. In fact, I'd say that neurosurgical training is likely to select for individuals who: 1) aren't deeply thoughtful--or even curious--about how the great, big world works, outside of neuroanatomy and its associated pathologies; and 2) are supremely confident and certain about what they do know (a necessity if one is going to cut into brain tissue). It's actually pretty easy to understand how, if anything, such training could reinforce the sort of willful ignorance expressed by Ben Carson. Contrary to the oddly popular stereotype, you don't need to be a super-genius with extraordinary powers of intellectual synthesis to be a neurosurgeon. In fact, such qualities would probably get in the way.