A speech recognition system receives and analyzes speech input from a user in order to recognize and accept a response from the user. Under certain conditions, information about the response expected from the user may be available, In these situations, the available information about the expected response is used to modify the behavior of the speech recognition system by taking this information into account. In one embodiment, the modified behavior of the speech recognition system comprises adjusting the rejection threshold when speech input matches the predetermined expected response. The modified behavior of the speech recognition system according to other embodiments of the invention include comparing the observed speech features to the models of the expected response separately from the usual hypothesis search in order to speed up the recognition system; modifying the usual hypothesis search to emphasize the expected response; updating and adapting the models when the recognized speech matches the expected response to improve the accuracy of the recognition system