Timing is everything: Early identification and the Double Deficit Hypothesis
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The Double Deficit Hypothesis of dyslexia posits that students can be grouped into four distinct groups: (a) average readers, (b) students with phonological deficits, (c) students with naming speed deficits, and (d) students with double deficits: those having both (b) and (c). The present study examines the stability of the Double Deficit groups from Kindergarten to Grade 2. 214 children were assessed in Kindergarten and subsequently tested in early Grade 1, late Grade 1, and Grade 2. Tests administered at each time included measures of naming speed, phonological awareness, and a variety of reading measures. Discriminant analyses indicated that approximately 70% of Grade 2 children were successfully classified by Kindergarten measures. Contingency analyses indicated moderate stability from Kindergarten to Grade 2 and more movement between groups between Kindergarten and Grade 1. The Double Deficit groups differed in reading achievement at each testing time, with the Double Deficit group obtaining the lowest scores. Implications for early assessment and intervention are discussed.