Observers have found that the incredible skills of many “savants” reflect an incredible amount of time spent obsessively practicing or memorizing one thing—-like say the calendar—-allowing them to perform impressive feats—-like telling you the day of the week for any date within 1000 years almost instantly.
But, there’s another aspect to some Autistic savants. Researchers have found that some savants have reduced activity in the parts of the fore-brain that are responsible for what we usually think of as information processing—-basically the part of the brain that packages information in a way we understand.
In you, presumably, this part of the brain takes a bunch of lines drawn on a piece of paper and tells you that it’s, say, a house. If you wanted to draw it later, this part of your brain would remember “house” and then try to rebuild the lines from that memory, plus the sensory memories that accompanied it. This is why most people’s drawings of a house are house-like, but hardly photo realistic.
In the savant, that first step is suppressed. So they see the lines, but they don’t remember it as “house,” they remember it as “bunch of lines.” So, later, when they try to draw it, there’s no interference from this organizing principle. They just reproduce the lines, sometimes in an order that would make no sense to a non-savant (part of the roof, than a corner of a window, then the top half of the door), and can reproduce it with startling accuracy.
The same thing can happen with numbers, allowing for really fast calculation since they don’t have to stop and consider the numbers as “numbers,” but just run the operations directly.
Again, this isn’t super common. And I don’t know how widely accepted this explanation is, but I’ve always found it nifty.