Communicative and sensorimotor development of Down's syndrome children.

Imperative and declarative performative behavior was examined in nonretarded and Down's syndrome children operating at two stages of sensorimotor intelligence. In both groups, more advanced types of performative behavior generally associated with a higher sensorimotor stage. Relative to the nonretarded children of the same sensorimotor stages, the Down's syndrome children relied more heavily on gestures in their imperative and declarative usage. Evidence was also obtained suggesting that the correspondence between sensorimotor stage and performative behavior is closer at younger ages than at older ages.