Deaf people have limited access to speech. Although some of them can comprehend written text at the same level as hearing people. We do not know what causes the differences in reading comprehension among deaf people, hearing native speakers of Japanese, and Japanese-language learners. This study examines reading comprehension differences among deaf people, hearing native speakers of Japanese, and Japa- nese-language learners using event-related brain potentials (ERPs).

We conducted experiments to examine responses to reading sentences with case-assignment violations. The results are as follows. (1) Deaf readers had both N400 and P600 responses to incongruent sentences. (2) Hearing native speakers had only P600 responses to incongruent sentences. (3) Learners had neither N400 nor P600 responses. These results show that deaf and hearing people may process written text differently. They also suggest that there is no reason for providing deaf people with the same literacy and reading edu- cation as the hearing.