Idiot savant calendrical calculators: maths or memory?

Eight idiot savant calendrical calculators were tested on dates in the years 1963, 1973, 1983, 1986 and 1993. The study was carried out in 1983. Speeds of correct response were minimal in 1983 and increased markedly into the past and the future. The response time increase was matched by an increase in errors. Speeds of response were uncorrelated with measured IQ, but the numbers were insufficient to justify any inference in terms of IQ-independence. Results are interpreted as showing that memory alone is inadequate to explain the calendrical calculating performance of the idiot savant subjects.