Phoneme Monitoring in Developmental Dyslexia: Pupillometric Evidence for Cognitive Rather than Acoustic Origins of Phonological Deficits

Background. Developmental dyslexia (DD) is a neurodevelopmental disorder characterized by persistent difficulties acquiring fluent reading. A core feature is impaired phonological processing, though its etiology remains debated. Two competing accounts attribute phonological deficits either to reduced acoustic sensitivity to lexical stress cues or to insufficient cognitive support during phoneme processing. Methods. To test these accounts, 57 Italian children (28 with DD, 29 typically developing) completed a phoneme monitoring task in which targets appeared in strong or weak syllables, varying in acoustic salience. A composite acoustic salience factor was derived from target cue properties, and an individual cognitive factor was computed from IQ, working memory, and shifting attention. Pupillometry was used to assess auditory sensitivity to acoustic salience and cognitive effort in real time. Results. The results showed that, behaviourally, children with DD showed significantly lower target identification accuracy and d’-sensitivity. However, pupil dilation during target processing did not differ between the two groups, while children with DD showed reduced pupillary responses on trials involving distractor rejection and missed targets. These physiological patterns correlated primarily with individual cognitive scores rather than acoustic salience. Conclusions. Taken together, these findings point toward an important role of individually varying cognitive resources during phonological processing and highlight the value of pupillometry as a sensitive, real-time index of cognitive engagement during a phonological task.