Examining the Double-Deficit Hypothesis in an Orthographically Consistent Language

We examined the double-deficit hypothesis in Finnish. One hundred five Finnish children with high familial risk for dyslexia and 90 children with low family risk were followed from the age of 31/2 years until Grade 3. Children's phonological awareness, rapid naming speed, text reading, and spelling were assessed. A deficit in rapid automatized naming (RAN) predicted slow reading speed across time and spelling difficulties after Grade 1. A deficit in phonological awareness predicted difficulties in spelling, but only in the familial risk sample. The effect of familial risk was significant in the development of phonological awareness, RAN, reading, and spelling. Our findings suggest that the basic premise of the double-deficit hypothesis-that RAN and phonological awareness are separable deficits with different effects on reading and spelling outcomes-holds also in a consistent orthography.