Got to hand it to him!
My sister had downs syndrome, and it is amazing the capacity she had to become an expert in a subject. In her case it was flowers. Shown a picture, she'd tell you what it was, where it grows, what it was called in Latin and if she'd ever seen one for real and where. All this from someone who, for all intents and purposes was a 5 year old in an adults body, couldn't read anything other than basic Janet & John type books so had memorized the names from being told.