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.
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.
Repeated measures ANOVA revealed a significant main effect of script type. Reading non-vowelized texts resulted in significantly higher cognitive load scores (p < .001), longer reaction times in the dual-task (p < .01), and poorer performance on the reading span task (p < .01) compared to the vowelized condition. Eye-tracking data showed significantly longer average fixation durations (p < .05) and a higher number of regressions (p < .01) for non-vowelized texts.
The findings indicate that the orthographic complexity of standard Persian script, primarily driven by short vowel omission, imposes a significant additional demand on working memory resources and increases cognitive load during reading. This suggests that visual word recognition in Persian is less automatic and requires more top-down processing, potentially affecting reading fluency and comprehension efficiency. Implications for educational practices and reading models are discussed.