Parafoveal Processing and Transposed-Letter Effects in Developmental Dyslexic Reading

During reading, adults and children independently parafoveally encode letter identity and letter position information using a flexible letter position encoding mechanism. The current study examined parafoveal encoding of letter position and letter identity for dyslexic children. Eye movements were recorded during a boundary-change paradigm. Parafoveal previews were either an identity preview (e.g., nearly), a transposed-letter preview (e.g., enarly) or a substituted-letter preview (e.g., acarly). Dyslexic readers showed a preview benefit for identity previews, indicating that orthographic information was encoded parafoveally. Furthermore, dyslexic readers benefitted from transposed-letter previews more than substituted-letters previews, demonstrating that letter identity was encoded independently to letter position during parafoveal processing. Although a transposed-letter effect was found for dyslexic readers, they demonstrated a reduced sensitivity to detect transposed-letters in later measures of reading, that is, go-past times, relative to that found for typically developing readers. We conclude that dyslexic readers, with less rich and fully specified lexical representations, have a reduced sensitivity to transpositions of the first two letters of the upcoming word in preview. These findings are compatible with the view that orthographic representations of dyslexic children are not sufficiently specified.