Hand and gender differences in the organization of aiming in 5-year-old children.

The aim of the present study was to analyze the organization of aiming movements in right-handed children aged 5 years, depending on gender and hand used to perform the task. We first tested the hypothesis that aiming movements are predominantly organized in a feed-forward manner before the age of six. Using a direction pre-cueing protocol, we analyzed the effect of gender and hand used to perform the task on reaction time (RT), movement time (MT), spatial accuracy (SA) and acceleration profiles (APs) in children aged 5 years. Differences in RT between the uncued and pre-cued conditions suggest that the direction is actually specified prior to the execution of the movement at the age of five. However, the results also show significant hand and gender effects on MTs, spatial error and APs. Specifically, in girls, MT and kinematics profiles vary as a function of hand and target localization, whereas this is not the case in boys. In addition, SA is lower when aiming with the non-dominant hand in boys, but not in girls. These results suggest that multiple movement strategies are already available to the child at the age of five. Girls appear to be able to change movement strategy as a function of the constraints of the task, resulting in a stability of spatial accuracy (SA). On the contrary, the functional advantage of the right hand on MT and SA generally reported in right-handed males is not present in the boys at the age of five.