Using the head to stabilize action: Reaching by young children

Even seemingly simple reaching task requires complex integration or remapping of reference frames with respect to eye, head and hand. Head-centered reference frame and head movement may play important roles in natural tasks and in the development of reaching. To understand the underlying control mechanism that support smooth reaching in particular and the seamless coordination of head and hand movements more generally, a semi-naturalistic experiment is designed for 1 ½ to 5 years old children, in which children are free to reach or not reach for the ball coming out from the slots on the puppet show. The fine-grained head and hand motion data were recorded. The analysis results show that (1) All the children participants stabilize their heads right before the reach; (2) During the reach, the head and hands move synergistically in the similar directions. (3) Large and variable head movements co-occur with more variable and jerky reaches. The coupling of the head and hands may suggest a dynamical integration of multiple reference frames.