Trajectories of reading development: A follow-up from birth to school age of children with and without risk for dyslexia

In order to understand why some children are vulnerable to difficulties in their language development and their acquisition of reading skill, the Jyvaskyla Longitudinal Study of Dyslexia followed 200 Finnish children from birth to school age. Half of these children had a family history of reading problems and were considered at risk for dyslexia; the other half were not at risk. A novel analysis, mixture modeling, revealed four subgroups with differential developmental trajectories to early reading. The subgroups who showed either a "dysfluent trajectory" (n = 12; 11 at risk vs. I control) or a "declining trajectory" (n = 35; 24 vs. 11) contained more children with familial risk for dyslexia. The subgroup showing an "unexpected trajectory" contained equal numbers of at-risk and non-risk children (n = 67; 33 vs. 34). The subgroup displaying a "typical trajectory" (n = 85, 38 vs. 47) contained more children born without dyslexia risk. This differential development of skills revealed that there are at least three troubled routes along which a child may ultimately encounter difficulties in reading acquisition. The most explicit routes are characterized by problems in either phonological awareness, naming speed, or letter knowledge -problems that increase in severity with age.