Language and Development Seminar: Parafoveal processing and transposed-letter effects in dyslexic reading

During parafoveal processing, skilled readers encode letter identity independently of letter position (Johnson, Perea, & Rayner, 2007). If dyslexia is linked to deficits in attention allocation and letter position encoding (e.g. Whitney & Cornelissen, 2005), letter identity and letter position information may not be extracted from the parafovea for dyslexic readers. In two experiments, eye movements of skilled readers and readers with dyslexia were recorded during a boundary paradigm experiment (Rayner, 1975). The participants in Experiment 1 were adults, whereas those in Experiment 2 were children. In both Experiments, parafoveal previews were either identical (e.g. nearly), a transposed-letter preview (e.g. enarly), or a substituted-letter preview (e.g. acarly). Dyslexic and non-dyslexic readers demonstrated orthographic parafoveal preview benefits during silent sentence reading and all reading groups encoded letter identity and letter position information parafoveally. However, dyslexic children showed a delayed preview benefit compared to typically developing children matched on chronological age, but similar results to typically developing children matched on reading age. Dyslexic adults, however, showed a greater dependence on letter position information for lexical identification during parafoveal processing compared to the skilled adult readers. Furthermore, whilst dyslexic readers showed the usual difference in foveal eye movement behaviour compared to age matched controls (e.g. longer viewing durations, more fixations), dyslexic children also showed different eye movement patterns compared to typically developing children matched on reading age. Thus, the current findings demonstrated that dyslexic readers show consistent and dyslexic-specific reading difficulties in both foveal and parafoveal processing during silent sentence reading.