<p>This study aimed to investigate how semantic and syntactic parafoveal processing differ between fluent left-to-right and non-fluent right-to-left reading directions in individuals accustomed to left-to-right reading. A self-paced rapid serial visual presentation (RSVP) task was employed to evaluate semantic and syntactic congruency effects. Participants, familiar with left-to-right reading, were tested under conditions simulating both fluent left-to-right and non-fluent right-to-left reading directions. In the fluent left-to-right reading presentation, both semantic and syntactic congruency effects were significantly observed in the RVF. Conversely, in the non-fluent right-to-left reading presentation, syntactic congruency effects were observed in the LVF, while semantic congruency effects were notably absent. Additionally, syntactic congruency effects emerged at the LVF in left-to-right reading presentation and at the RVF in right-to-left reading presentation, demonstrating the flexibility of syntactic processing mechanisms across reading contexts. The findings reveal a dissociation between semantic and syntactic processing in parafoveal regions based on fluency of reading direction. Syntactic information serves as a foundational element, adaptable across reading contexts, emphasizing its hierarchical role in parafoveal processing. The current study provides a basis for future exploration of cross-linguistic variations and cognitive adaptations in reading behavior.</p>