The interrelationships between motor, cognitive, and language development in children with and without intellectual and developmental disabilities.

It is generally agreed that cognitive and language development are dependent on the emergence of motor skills. As the literature on this issue concerning children with developmental disabilities is scarce, we examined the interrelationships between motor, cognitive, and language development in children with intellectual and developmental disabilities (IDD) and compared them to those in children without IDD. In addition, we investigated whether these relationships differ between children with different levels of cognitive delay. Seventy-seven children with IDD (calendar age between 1;0 and 9;10 years; mean developmental age: 1;8 years) and 130 typically developing children (calendar age between 0;3 and 3;6 years; mean developmental age: 1;10 years) were tested with the Dutch Bayley Scales of Infant and Toddler Development, Third Edition, which assesses development across three domains using five subscales: fine motor development, gross motor development (motor), cognition (cognitive), receptive communication, and expressive communication (language). Results showed that correlations between the motor, cognitive, and language domains were strong, namely .61 to .94 in children with IDD and weak to strong, namely .24 to .56 in children without IDD. Furthermore, the correlations showed a tendency to increase with the severity of IDD. It can be concluded that both fine and gross motor development are more strongly associated with cognition, and consequently language, in children with IDD than in children without IDD. The findings of this study emphasize the importance of early interventions that boost both motor and cognitive development, and suggest that such interventions will also enhance language development.