Indeed, this was born out in an experiment done about 20 years ago involving a mediocre math student who agreed to completely immerse himself in math for some extended period (a month, at least IIRC). At some point he crossed a remarkable threshold and became able to perform calendar calculations and other feats thought only to be possible for autistic savants.
In chapter 13 of Musicophilia Oliver Sacks discusses the unusually heightened musical abilities of blind people. In chapter 14, though, he discusses the unusually heightened musical abilities of people with synesthesia. Then, in chapter 18 he discusses the unusually heightened musical abilities of people with Tourette's Syndrome.
What is clear from all this (from the experiences of the mediocre math student, through the memory skills of London cabbies, and the musical abilities of the blind, synesthetic, and touretters) is that autism is not the touchstone of extraordinary abilities: any condition or circumstance that causes a person to focus in a sustained, deliberate, exclusive way on a particular activity will lead to them becoming more and more skilled at that activity.
The average person can, but simply will not, cut so many other things out of their life that they are able to authentically excel in one thing. (I should probably turn that around: the average person can't cut many basic things out of their life: earning a living, elementary social interactions, ordinary daily maintenance of person and property, preclude single minded, obsessive focus on skills like the mental calculation of calendar dates, instantaneous counting of large numbers of objects, or the recall of every word they've ever read.) But cutting all those other things out is a choice that autistic people never have to begin with: they can't make sense of them, and focus, by default, on things they can grasp, and those things become their world.
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