Development of early motor skills and language in children at risk for familial dyslexia.

Differences in motor development and the relationship between motor and language development were studied in 88 children with familial risk for dyslexia (43 females, 45 males; at-risk group) and 88 children without familial risk for dyslexia (35 females, 53 females; control group; n=176) during the first two years of life. A structured parental questionnaire was used to assess motor development. Expressive language skills were assessed at the age of 18 months with the Reynell Developmental Language Scales and at 18 and 24 months with the MacArthur Communicative Development Inventories. At group level, the motor development of children in both the at-risk and control groups was similar. However, motor development showed a different pattern in these groups. Cluster analyses revealed three clusters in the control group: 'fast motor development', 'slow fine motor development', and 'slow gross motor development'. In the at-risk group, only two clusters were found: 'slow motor development' and 'fast motor development'. A significant difference (p=0.03) was found between the clusters in the MacArthur Communicative Development Inventories. Children with familial risk for dyslexia and slow motor development had a smaller vocabulary and produced shorter sentences than the all other children. Associations between motor and language difficulties are discussed.