The structure of savant calendrical knowledge.

Aim We aimed to explore the organization of the calendar knowledge base underlying date calculation by assessing the ability of savant calendar calculators to free recall a series of date lists. Method Four experiments are reported that assessed recall of structural and non-structural features of the calendar in eight savant calendar calculators (seven males; one female; median age 34y 6mo; age range 2747y), five of whom had a diagnosis on the autism spectrum. The inclusion criterion was a genuine calculation ability rather than an interest in dates. Results Mean recall was facilitated for material organized according to the structural features of a calendar (leap years, dates falling on the same weekday, dates occurring at 28y intervals) but not for a non-structural calendar feature (Easter Sunday). Interpretation Distinctions are drawn between two sources of savant calendar-related knowledge, structural and event related. It has been suggested that structural knowledge plays a key role in the acquisition and operation of savant date calculation skills.