I'm not usually one to bang the "everything must be scientific" drum, but the claims some typographers make seem to be so unscientific as to be absurd. I know t

I'm not usually one to bang the "everything must be scientific" drum, but the claims some typographers make seem to be so unscientific as to be absurd. I know that much of typography is subjective, but still: In this case I prefer the text on the right, but how do we know this is due to "vertical rhythm" and not simply increased space between lines? (Or some other effect.) This would be easy to test.