"We found some common principles in the way people look at art and a large variability depending on the subjects’ own interests, artistic appreciation, and knowledge. This large subject-to-subject variability makes the scientific study of art very challenging. It is indeed very difficult to find common principles but this lack of uniformity and objectivity is perhaps one of the reasons that make art so unique, personal and fascinating."
Being a small study, I don't give it a whole lot of weight. But, it's food for thought and discussion.
They found previous knowledge of the artwork to affect the eye tracking. So, if we create art of similar genres, would that affect the eye tracking as well? It's another thing to consider in photography: did the "rules" we read about exist before or after we acclimated to iconic prints?
And, if the viewers are so subjective in their viewing, how can their be so much objective advice about your viewers?
Yet another reason to ignore the rules.