Temporal sequence of morpheme boundary detection and positional encoding in the early stage of visual morphologically complex word recognition: an ERP study on Korean words

This study investigated the time course of visual recognition of morphologically complex words by examining ERP components related to transposition confusability and the morpheme boundary effect. EEG (electroencephalogram) data were recorded during a lexical decision task using Korean nonword stimuli under three experimental conditions: syllable transposition within a morpheme boundary (TSW), across-morpheme boundaries (TSA), and a control with replaced syllables (RS). Behaviourally, the morpheme boundary modulated the transposition effect, showing significant differences in accuracy and reaction time between TSW and RS, but not between TSA and RS. ERP results revealed greater negative amplitudes of N250 and N400 in TSW compared to RS, indicating a transposition effect. Additionally, greater negative amplitudes of N150 were observed in TSA compared to TSW and RS, and no N400 difference between TSA and RS. These findings suggested that morpheme boundary detection occurs early in visual word recognition, eliminating the confusability effect of syllable transposition.