An analysis of calendar performance in two autistic calendar savants.

We acquired large data sets of calendar performance from two autistic calendar savants, DG and RN. An analysis of their errors and reaction times revealed that (1) both individuals had knowledge of calendar information from a limited range of years; (2) there was no evidence for the use of memorized anchor dates that could, by virtue of counting away from the anchors, allow correct responses to questions about other dates; and (3) the two individuals differed in their calendar knowledge, as well as in their ability to perform secondary tasks in which calendar knowledge was assessed indirectly. In view of the fact that there are only 14 possible annual calendars, we suggest that both savants worked by memorizing these 14 possible calendar arrangements.