Nick, I think if you do a bit of Googling about it you'll find that the eye is drawn first to bright areas. This is why an image, of whatever type, that has strong, overly bright areas will generally be criticised for those. Because the eye goes there first and then continues to be drawn to those areas to the exclusion of other areas.
Justan, I'm not disputing the validity of Rembrandt's techniques. What I'm saying is that they're already well known and that these types of scientific studies aren't needed to make them well known.
With respect to an innate sense of what is pleasing to the eye, I'm talking in generalities. There are certain genres that don't really follow any of the known compositional cues or guidelines. The Abstract Expressionists, for example. Pollack, Frank, Koonig, Newman. Much of their work was really without any regard to traditional composition. So sure, when you get works like those that are so far out of the 'norm' there's going to be a fair debate about the validity of the works as art. Why? Because to a lot of people those types of works aren't pleasing to the eye. As a photoimpressionist photographer, I'm more than a little familiar with that debate.
Even if some form of 'accepted' compositional tools are used, the subject matter of a piece may be offensive to some. That doesn't have anything to do with the composition but there may still be debate about the validity of the work as art. Plenty of reasons beyond the concepts of composition for there to be debate about what is or isn't art.
As far as directional lines, I've seen writings in the past that support the position. My own, informal, research supports the position as well. I've taken the same image with lines leading from left to right then flipped it so the lines went from right to left and posted them for comment. The majority, and not a small majority, of those of Western origin prefer the lines leading from left to right. Definitive? Probably not. Anecdotally supportive? I'd say so.
You quoted my comment "Many artists already 'make sense' of these without...." twice. What are you referring to when you speak of 'codified science providing increased impact in the realm of art'? But as far as 'definitive guides' go, there are already plenty out there. There are countless guides on art composition to be found. Hell I've got a few basic articles on my website. Even then; however, I'm very wary of getting too scientific with the study because then we run the risk of everything looking essentially the same and art becoming a scientific, paint by numbers, insert figure A into position B and object C into position D exercises. The measurebators here on LuLa already take the art of photography far too far into the science realm. We run the risk of losing the innovators like the Impressionists or the Abstract Expressionists or the Cubists because everything just becomes bland and, for lack of a better term, Kincadeified.