David Brown describes a simple way to do a “savant” trick: calculate the day of the week for any specified date. (For example: was March 12, 1401, a Sunday, a Monday, a Tuesday, a Wednesday, a Thursday, a Friday, or a Saturday?) He says:
My point here is simply to suggest that though some savant feats are remarkable, things like this can be explained more simply. That a savant may be an idiot, surrounded by a sea of disability, I don’t think, requires us to overestimate what is involved in the little they can do. I should think it’s quite possible for some, to have above average ability in one area and subnormal in many others.