Accuracy and Variability in Goal Oriented Movements – Decomposing Gender Differences in Children

An essential ability of the motor system is to achieve specified goals with great reliability while the movement trajectories themselves cannot be repeated in an identical fashion. Variability is therefore often different in the outcome and the execution. With this distinction improvements in performance with practice are accompanied by a decrease in variability that can be accounted for by three orthogonal components: ”Tolerance”, “Noise Reduction”, and “Covariation”. Central to this decomposition is that performance success is investigated in relation to the dispersion of the variables in execution. This method is applied to a learning study where 12-13-year-old boys and girls practice a virtual skittles task (throwing a ball to hit a target skittle). The results revealed that gender differences in the learning process were present. Boys showed a higher initial level of proficiency in the novel task were significantly faster than girls in finding successful solutions. The variability decomposition reveals that the component tolerance is exploited first in both boys and girls, however much more quickly by boys. This aspect of improvement is followed by noise reduction at an equal rate in both genders. Covariation played a subordinate role. The same sequence of stages was observed in a previous study on adult learners.