When roberto observes his two children drawing, he notes a striking difference in their motor behaviors. two-year-old mona makes crude drawings utilizing mostly upper-arm movement, whereas 6-year-old mary makes very precise strokes utilizing fine finger movements. this difference is best explained by the principle.

Now, I'm not totally sure, but it seems like the answer could definitely be the Proximodistal. after a quick google search I found this article discussing proximodistal development. It said that as children grow older, they start to gain control of their motor skills a little better. More specifically, it gave an example of an infant learning to use their shoulders before being able to make finer movements with their fingers. The proximodistal principle states that control of the body stems from the center of the body and then branches outward from there. take it for what you will but that's the answer that caught my eye.