The analysis of errors in non-native language performance, or Error Analysis, assumed a new role in applied linguistics in the late 60s and a series of studies have attempted to account for different types and causes of errors. Under the conventional error analysis, however, learners' errors in foreign languages have been evaluated irrespective of their effect on communication.

Following Burt and Kiparsky (1974)'s distinction between global and local errors, a lot of research results prove that some errors are more important than the others in terms of communication. Considering that more and more foreign language teachers have begun to realize the importance of communication in foreign language teaching, this must be reflected in the principle of error evaluation, such as deciding the rank of error gravity for error correction.

The present article, regarding communication as the primary aim in foreign language teaching instead of conformity, insists that error evaluation should be given more weight and reviews some previous researches investigating the comprehensibility of errors.