The Impact of Persian Script Complexity (Elimination of Short Vowels and Letter Connectivity) on Working Memory Capacity and Cognitive Load during Reading

Mohseni Hanjani, Farideh; Lotfi Azimi, Afsaneh

doi:10.22034/iepa.2025.557827.1550

The Impact of Persian Script Complexity (Elimination of Short Vowels and Letter Connectivity) on Working Memory Capacity and Cognitive Load during Reading

Document Type : Original Article

Authors

Farideh Mohseni Hanjani ¹

Afsaneh Lotfi Azimi ²

¹ Department of Persian Language and Literature, S.T.C, Islamic Azad University, Tehran, Iran.

² Department of Educational Psychology, S.T.C., Islamic Azad University, Tehran, Iran.

https://doi.org/10.22034/iepa.2025.557827.1550

Abstract

Objective: The Persian writing system is characterized by features such as the optional omission of short vowels (diacritics) and obligatory letter connectivity, which may increase its orthographic complexity. This study investigated the impact of this inherent complexity on working memory capacity and cognitive load during reading texts.
Method: A within-subjects design was employed with 45 skilled adult Persian readers. Participants read texts under two conditions: (a) Vowelized (with full diacritics), and (b) Non-Vowelized (standard script). Working memory capacity was assessed using a reading span task administered after each condition. Cognitive load was measured via a self-report 9-point Likert scale and a dual-task paradigm (secondary reaction time task). Eye-tracking metrics (fixation duration and regressions) were also recorded.
Results: Repeated-measures ANOVA revealed a significant main effect of script type across all measures. Reading non-vowelized texts led to significantly higher subjective cognitive load scores (p < .001), longer reaction times in the dual-task paradigm (p < .001), and lower performance on the reading span task (p < .001) compared to vowelized texts. Eye-tracking data showed significantly longer average fixation durations (p < .001), more regressions (p < .001), shorter forward saccades (p < .01), and longer first-pass reading times (p < .001) for non-vowelized texts. Bonferroni-corrected pairwise comparisons confirmed these effects, and hierarchical regression analyses indicated that working memory capacity moderated the impact of script type on reaction time but not on accuracy. Qualitative analysis further revealed that readers employed compensatory strategies such as rereading and context-based vowel inference during non-vowelized reading.
Conclusions: The findings demonstrate that the orthographic complexity of standard Persian script, particularly the omission of short vowels, imposes substantial cognitive demands on working memory and increases overall cognitive load. Non-vowelized reading requires greater top-down processing and less automatic visual word recognition, affecting reading fluency and comprehension efficiency. Both quantitative and qualitative evidence indicate that readers adopt adaptive strategies to cope with this complexity. These results have implications for reading instruction, text design, and theoretical models of reading in vowel-optional scripts, highlighting the importance of orthographic transparency and cognitive resource allocation.

Keywords

Orthographic Complexity

Working Memory

Cognitive Load

Persian Script

Reading Processes

Vowel Diacritics

Subjects

Learning

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