Individual differences in language development: relationship with motor skill at 21 months.

Language development has long been associated with motor development, particularly manual gesture. We examined a variety of motor abilities - manual gesture including symbolic, meaningless and sequential memory, oral motor control, gross and fine motor control - in 129 children aged 21 months. Language abilities were assessed and cognitive and socio-economic measures controlled for. Oral motor control was strongly associated with language production (vocabulary and sentence complexity), with some contribution from symbolic abilities. Language comprehension, however, was associated with cognitive and socio-economic measures. We conclude that symbolic, working memory, and mirror neuron accounts of language-motor control links are limited, but that a common neural and motor substrate for nonverbal and verbal oral movements may drive the motor-language association.