1. A method for recognizing characters, the method comprising steps of: providing a set of reference vectors, each of the reference vectors representing a category, the reference vectors being derived from writing samples provided by non-specified writers; performing a preliminary character recognition operation on plural input characters to make a preliminary determination of the category to which each of the input characters belongs by comparing a feature vector of the one of the input characters to the reference vectors to determine a candidate category and to generate a recognition result; with reference to the recognition results for the plural input characters, selecting each of the input characters that has been recognized with high reliability as a selected input character; predicting, from the feature vector of each selected input character, a writer-specific feature vector for at least one category other than the candidate category of the selected input character; generating a writer-specific reference vector for each category using the writer-specific feature vector predicted for the category; and performing a final character recognition operation using the writer-specific reference vectors to make a final determination of the category to which each of the input characters belongs.