This study proposes a computer-assisted language learning (CALL) system for increasing error
awareness, aiming for correct English usage and improvement of English proficiency of learners. The
system incorporates two principles: learning from negative evidences, and prioritizing communication
errors. Negative examples, specifically erroneous sentences, are extracted from learner corpus, to
create practice exercises. These exercises constitute an intelligent practicing system, by exposing
adaptively to abilities and weaknesses of each user, determined by his responses while using the
learning system. Among all type of errors in the exercises, ones that impaired understanding, socalled
communication errors, gain priority for being studied. Unlike traditional language instructions,
actual frequent errors made by learners in general are emphasized, while individual errors are
corrected. Moreover, learners are directed to focus on their weaknesses and unintelligible errors, thus
it is considered as a straightforward and effective method. To evaluate, experiments are conducted by
target users, which are Japanese learners. After using prototypes, evaluation is done in aspects of
adaptive mechanism, learning achievement, and satisfaction of learners. The overall result concludes
that the system has more potential to improve English ability than traditional non-adaptive approaches.
At the end, recommendations for future improvements are discussed.