Abstract
To understand the development of visual tracking ability during childhood, upper limb motor functions of 405 children aged 3–12 years and 52 adults aged 20 years (control) were evaluated. We calculated 12 parameters, namely, the mean values and standard deviations of radial deviation, angle deviation, movement distance per each sampling time, pen pressure, and pen pressure variability, residual sum squares of the power spectrum of acceleration in X axis and residual sum squares of the power spectrum of acceleration in Y axis. Then, factor analysis was applied against these parameters, and 3 factors were identified to be important; these 3 factors were the skillfulness of drawing, stability of tremor, and stability of pen pressure. Our results show that the curve for development of skillfulness of drawing and stability of tremor against increasing age was hyperbolic. The stability of pen pressure showed linear development until an age of 6 or 7 years and little development after that age. Therefore, we think that a three-dimensional model can be used to describe the development of visual tracking ability.
