Learning to grasp efficiently: the development of motor planning and the role of observational learning.

We examined whether 18-, 24-, and 42-month-old children, like adults, prospectively adjust their hand movements to insure a comfortable hand posture at the endpoint, and whether children can learn to grasp efficiently by observation. The task required grasping a bar and fitting it into a hollow cylinder in order to make it light up. Measures of quantitative (grip height), as well as qualitative (grip type) prospective grip adaptation were analyzed. Grip height adaptation was found reliably by 24 months, grip type adaptation by 3 years. The ability to learn efficient grasping by observation seems however very restricted.