Savant syndrome, characteristically, consists of left hemisphere dysfunction coupled with right hemisphere emergence, and what you see in the savant are basically right brain skills.

I have a fairly strict definition of early infantile autism. That is not to say that people who don't meet that classic description don't have autism, but we might do well to narrow our definitions, and our samples, down to groups that are very similar, because I think you're more likely to find the cause.

Now I realize, and I acknowledge, that the right brain/left brain distinction is a tremendous oversimplification. We don't come neatly divided into right and left hemispheres, but the fact is that the two hemispheres of the brain do specialize in certain functions.

Savant syndrome is not a disorder in the same way as autism is a disorder or dementia is a disorder. Savant syndrome are some conditions that are superimposed and grafted on to some underlying disability. So savant syndrome is not a disease or disorder in and of itself. It is a collection of characteristics, or symptoms, or behaviors that have grafted on to the underlying disability.

There are some cases that have come to my attention where there's been a head injury, or getting struck by lightning and surviving, with really no disability or residual. So there are cases that I'm aware of where there's been some incident which triggered the acquired savant ability, but is not associated with long term disability, so that can occur. But I think that's probably the exception rather than the rule in that I think many of the acquired savants do end up with some residual disability.

The term syndrome generally appears to be a constellation, or collection, of similar traits or behaviors within an individual. So, savants do have sort of a constellation of symptoms, which is characterized by some spectacular skill, or skills, coupled with this massive memory which is grafted on to some underlying disability. So those three conditions quantify, in my mind, the term syndrome.

A savant, by definition, is somebody who has a disability and, along with that disability, has some remarkable ability. Prodigies and geniuses have the remarkable abilities that the savant shows, but they do not have a disability. So, by definition, a savant includes someone with a disability, and a prodigy or genius are people who have these remarkable skills but they do not have a disability.