Idiot savant calendrical calculators: rules and regularities.

The three experiments described aimed to establish whether the achievements of idiot savant calendrical calculators were based solely on rote memory and arithmetical procedures, or whether these subjects also used rule-based strategies. It was found that, although different structural calendar regularities were tested by using differing experimental paradigms, all subjects could at least use some of the rules under investigation. The more cognitively able subjects could make use of all the three structural regularities of the calendar tested here. It was concluded that idiot savant calendrical calculators can use rule-based strategies to aid them in the calculation of the days on which past and future dates fall.