Laterality in Children: Evidence for Task-Dependent Lateralization of Motor Functions.

The behavioral preference for the use of one side of the body starts from pre-natal life and prompt humans to develop motor asymmetries. The type of motor task completed influences those functional asymmetries. However, there is no real consensus on the occurrence of handedness during developmental ages. Therefore, we aimed to determine which motor asymmetries emerged differently during childhood. A total sample of 381 children in grades 1 to 5 (6-11 years old) of primary school were recruited and tested for two fine coordination tasks (Floppy, led by dexterity, and Thumb, led by speed-dominated skills) and handgrip strength (HS). Data about their handedness, footedness and sports participation were also collected. Children performed better with their dominant side, especially for the Floppy and HS tests. The asymmetries were more marked in right-handed children and did not differ by age, gender or type of sport. Our findings support the thesis of a functional lateralization in complex coordinative tasks and in maximal strength during developmental ages. Furthermore, our findings extend the evidence of a stronger lateralization in right-handed individuals, demonstrating it at a functional level in primary school children performing motor tasks. Fine motor skills allow a "fine" understanding of developmental trajectories of lateralized behavior.