Grapheme-phoneme conversion in Korean Word Recognition: Evidence from event-related potentials

Although Hangul, the Korean alphabet, is orthographically shallow, the phonological rules cause difficulties for dyslexic children in reading and writing. We investigated the difference in grapheme-phoneme conversion (GPC) of Korean words and nonce words when phonological rules are applied. Based on the dual route theory, we tried to explain the activation of the GPC route. Methods: We recorded EEGs from 28 native Korean adults while they were conducting a phoneme judgment task in which they were asked to decide whether the pronunciation of the visual word was identical to the corresponding auditory word. Response accuracy rate, reaction time, and N250 waveforms were analyzed for phonological processing in word recognition. Results: For the mean response accuracy rates and reaction times of the phoneme judgment task, there was a significant main effect of the stimulus word category and of the applied rules. The event-related potential (ERP) showed significantly smaller amplitude of N250 in words than in nonce-words. Specifically, for the words, the N250 waveform was smaller in incorrect pronunciation than with correct pronunciation. However, there was no significant effect in nonce words. Conclusion: The result provides support for the dual route model of reading and writing. In Korean word recognition, people automatically apply phonological rules with familiar words, however, GPC causes a delay when recognizing unfamiliar words.