1. A method of performing automatic speech recognition, the method comprising: determining whether a user's utterances relate to one of a plurality of corpora of data having modified probabilities of certain words; if the user's utterances relate to one of the plurality of corpora of data, selecting the related corpora of data for use in speech recognition; receiving speech from a user, the speech including at least one speech error; and using the selected corpora of data having modified the probabilities to process the received speech to increase the probability of correctly interpreting the received speech with the at least one speech error.