Visuo-manual aiming movements in 6- to 10-year-Old children: evidence for an asymmetric and asynchronous development of information processes.

Sixty children from 6 to 10 years old participated in an open-loop visuo-manual aiming task (Experiment 1). They were asked to point as fast and accurately as possible toward lateralized visual targets. Responses were wrist flexion-extension movements. Results showed non-monotonic changes with age of constant error, reaction time, and movement time. Constant error for targets presented in the right visual field increased between 6 and 8 years and decreased afterward. Reaction time and movement time decreased with age except at 8 years where they tended to increase. The same subjects participated in two control tasks. One task was designed to test the spatial localization of the lateralized visual targets (Experiment 2). Results showed that subjects localized very accurately the targets at all ages. The second control task was designed to test simple reaction time to the same visual stimuli used in the previous tasks (Experiment 3). Results indicate that reaction time decreased linearly with age when no spatial processing is required for the production of the response. The results of the three experiments showed different developmental functions according to the processes involved in each task. Moreover, they suggest that the conversion from visual to motor coordinates undergo a qualitative change at 8 years of age, and that the prevailing process of this conversion is located in the left cerebral hemisphere.