Abstract
Children's motor control skills develop with age, but it is unclear when the development begins and ends. To identify those critical points, we conducted a wrist-tracking task and examined position and velocity controls in children and adults. The task consisted of a visible circular orbit, a tracer rotating at a constant speed of 0.1 Hz, and target-visible and -invisible subsections. We had three age groups for younger elementary school children (n = 16, 8.0 ± 0.8 years, Group 1), older elementary school children (n = 13, 11.6 ± 0.6 years, Group 2), and adults (n = 10, 23.5 ± 2.7 years, Group 3). Absolute angular position difference Δθ and absolute angular velocity difference Δω between the target and tracer were computed to compare the position and velocity control abilities among the groups. Statistical hypothesis tests on the control parameters revealed that the mean Δθ of Group 2 (4.06 ± 0.71 deg) was statistically smaller than Group 1 (6.17 ± 1.51 deg, p < 0.006) and equivalent to Group 3 (2.76 ± 0.51 deg, p < 0.075), whereas the mean Δω of Group 2 (19.8 ± 4.5 deg/s) was statistically equivalent to Group 1 (20.5 ± 2.9 deg/s, p < 1.0) but greater than Group 3 (12.9 ± 2.0 deg/s, p < 0.0011). It indicated that the older children performed comparably accurate position control to the adults but exercised immature velocity control. However, we noticed that velocity control in the older children was actively developing since they managed to decrease Δω significantly (17.4 ± 3.53 deg/s, p < 0.003) during the target-invisible phase, just like the adults did (11.8 ± 1.08 deg/s, p < 0.017). Therefore, we could also infer that children start to obtain feedforward abilities and internal models in preteens.