Rate-disabled versus accuracy-disabled subtypes of dyslexia: A longitudinal study from preschool to grade 1.

This longitudinal study investigated subtypes of dyslexia based on the distinction between word reading accuracy and word reading rate. Building on prior cross-sectional research, we inquired whether the cognitive profiles of these subtypes can be identified before children learn to read. A large sample of Hebrew-speaking children were assessed on phonological awareness (PA), morphological awareness (MA), and rapid automatized naming (RAN) in preschool and then followed into first grade to evaluate their reading accuracy and rate. In preschool, findings revealed two distinct subgroups: one with selective deficits in PA and MA but intact RAN (PA + MA-disabled) and another with impaired RAN but preserved PA and MA (RAN-only disabled). In first grade, as predicted, the PA + MA-disabled group demonstrated significantly lower reading accuracy compared to both the RAN-only disabled and control groups. The RAN-only subgroup exhibited slow reading but intact accuracy. However, contrary to predictions, the PA + MA-disabled group also exhibited slower reading rates. These results suggest that at the beginning of reading development, low levels of reading accuracy limit reading rate. Our study (i) supports accuracy-rate subtyping of dyslexia, (ii) reinforces the role of both PA and MA in achieving early word reading accuracy, and (iii) highlights the existence of a highly specific RAN-rate dyslexia subtype. These findings have significant implications for early diagnosis and intervention as well as the definition of dyslexia.