1. A method for the computer-assisted learning of orthography, the method comprising executing the following steps by a data processing system retrieving ( 11 ) a main set of words from a computer readable data storage medium; retrieving ( 12 ) an error data set associated with said main set of words from the computer readable data storage medium, the error data set comprising, a word error statistic associated with each word of said set; and a symbol error statistic associated with symbol pairs; repeatedly executing the following steps: selecting ( 13 ) a word to prompt a user with, by computing, for each word of the main set or a subset of the main set of words, from the word error statistic and the symbol error statistic, a combined statistic measure related to the probability of an error occurring in said word when it is input by the user, and selecting the word which has the maximum value of said statistic measure; prompting ( 14 ) the user with said word; accepting ( 15 ) a user input specifying a sequence of symbols representing said word; comparing ( 16 ) the user input with said word; updating ( 17 ) the word error statistic associated with said word according to the user input, and storing the updated word error statistic in the computer readable data storage medium; updating ( 18 ) the symbol error statistic according to the user input, and storing the updated symbol error statistic in the computer readable data storage medium.