Early predictors of reading comprehension difficulties

The aim of the present thesis was to examine the cognitive and language profile in children with poor reading comprehension using a longitudinal perspective. Even though comprehension skills are closely connected to educational success, comprehension deficits in children have been neglected in reading research. Understanding factors underlying reading is important as it improves possibilities of early identification of children at risk of developing reading problems. In addition, targeted interventions may prevent or reduce future problems. Descriptions of the cognitive and language profile in children with different types of reading problems from an early age and over time is an important first step. The three studies included in this thesis have been conducted using data from the International Longitudinal Twin Study (ILTS). In the ILTS, parallel data have been collected in the US, Australia, Sweden and Norway. Altogether, more than 1000 twin pairs have been examined between the ages 5 and 15 years using well known predictors of reading, along with decoding, spelling, reading comprehension and oral language measures. In the three studies, the Simple View of Reading has been used as a theoretical framework and children who exhibited different kinds of comprehension related difficulties have been identified at different ages. The studies include both retrospective and prospective analyses. The results across studies indicated a robust oral language deficit in all subtypes displaying comprehension problems. The oral language deficit was widespread and included vocabulary, grammar and verbal memory. In addition, the oral language deficit was manifested as compromised phonological awareness and print knowledge prior to reading instruction. Reading comprehension deficits were late emerging across studies in children with comprehension difficulties.