[wrp]

I've never seen or heard of a study of the mechanics of ballpoint pen manipulation. However, I have seen a considerable amount of handwritten correspondence from the early to mid-20th century. With the general change from fountain pens to ballpoints, there was a significant change in letter forms, particularly among female writers. The newer style is marked a reduction in straight vertical lines, a general trend to circular motions, and a slower advance along the line. This seems not surprising when you consider that quill/dip/fountain pen movement is more with the arm, while ballpoint movement is more with the fingers. So...it seems that a new form of cursive has already (informally) evolved to a degree.

[masgrimes]

What makes you think the change in penmanship specimens over that time period are more connected to the proliferation of the ballpoint pen instead of the changes in penmanship instruction?