Eye movement measures of word-level and text-level fluency in disordered reading: A comparison of schizophrenia and...

Deficits in language processing, executive functioning, and oculomotor control have been extensively reported in schizophrenia, all of which are crucial for skilled reading. However, only recently have studies identified reading impairments in schizophrenia, including more effortful eye movement reading behaviour relative to controls. Notably, similar deficits across these domains have also been reported in dyslexia (reviewed in Whitford et al., 2018). Given this overlap in reading-related systems, a recent eye-tracking study from our group directly compared global (sentence-level) reading behaviour in the two conditions, revealing comparable impairments in fluency and comprehension (Whitford et al., 2023). Building on this work, we employed eye movement measures of naturalistic story reading to examine both local (word-level) and global (text-level) reading behaviour in schizophrenia and dyslexia, with a particular focus on word frequency effects (an index of lexical accessibility). We further examined whether individual differences in executive functioning (inhibition and working memory via an antisaccade task) and language skills (phonological processing, word decoding, and reading comprehension via standardized assessments) modulated word frequency effects. Linear mixed-effects models revealed largely comparable global and local reading behaviour across the clinical groups, including comparably larger word frequency effects relative to controls (driven by slower processing of lower-frequency words). Moreover, stronger executive functioning and language skills exerted largely similar facilitatory influences on lexical processing, reducing word frequency effects. Taken together, our findings suggest that reading deficits in schizophrenia and dyslexia may reflect overlapping neurocognitive contributions, consistent with a transdiagnostic profile of reading impairment at the behavioural level.