When you're studying the brain there are, broadly, two approaches. One can start with the parts and the mechanisms, the neurons, ganglia, synapses, and all that crap, and try to build upwards. Alternatively, one can start from a high level, and observe what brains do when they're inside organisms.
Ideally, some day, the bottom-up and the top-down scientists meet in the middle and have The Answer. So far results are mixed. Ask the physicists how it's going, for instance. Or the biologists.
The first approach to Brains is, well, one could say it's in its early stages. Derek Lowe has an nice piece over on his blog. The executive summary is: there's this animal, a roundworm, with a 302 neuron brain and we have no idea how it works. We have some theories about how very small (e.g. 5) neuron clusters work. We're missing some fundamental thing, we're trying to understand a radio without knowing that inductance is a thing.
The second approach is working out very well indeed. We actually know an enormous amount about what the human brain does and how to manipulate it. We just don't have any idea how it does it it. We know, for instance, that one of the things human brains do extraordinarily well is model, estimate, what's going on in other human brains. We can, to a pretty fair degree, tell what other people are thinking. No, it's not perfect, it's not telepathy, but we're really good at reading body language and facial expressions and whatnot.
In even slightly broader strokes, we can characterize these two approaches as "how it works" and "what it does" or something similar.
There are several basic problems in cognitive science, rooted in the fact that we're studying the thing with the thing itself. One such problem is that the brain is a marvelously malleable thing, prone to suggestibility leading to errors.
This property makes this kind of science a little harder than other areas of science which are, just to review, incredibly hard to get right. Experimental science is a bitch, and almost all experiments performed are wrong and broken, not because the scientists are dumb but because science is really hard.
How does this apply to photography?
The two approaches apply here as well, with very similar results (largely because a lot of what's going on is cognitive science in disguise, being performed by dunderheads).
We have a lot of rules of composition, for instance. Every rule of composition suffers from the malleability of the brain. Once you learn about leading lines, you cannot help but observe that "they work". Whenever you notice such a thing in a picture, your thought process goes "aha, leading line" and your eyes obediently follow the leading line, because that's what you have learned happens, and then you judge the success of failure based on where your eyes land. When you do not notice the leading line, or there is none, you don't. By learning about leading lines, you have in a very literal sense destroyed your ability to judge their efficacy.
And so on for other rules of composition.
Actually doing science to determine what really works is hard, and nobody bothers with it. Instead, they make up arbitrary rules, teach their brains to like them, and start judging goodness based on the use of the arbitrary rules. Lo, their photographs magically "improve."
And on it goes through other facets of photography, we have people seriously doing lens reviews and taking pictures like this thing:
which looks like science, but since it's not actually measuring much of anything, is just a bunch of bullshit. Most of the test charts pasted to their stupid little wall are measuring an inextricable tangle of lens properties: field flatness, sharpness, and various aberrations.
If they're trying to produce measurements of interesting aspects of lens performance, they're failing because they're not handling flatness separately from other properties.
If they're instead trying to measure some holistic notion of how the lens will perform in real life, then they're providing very interesting data to people who exclusively photograph walls with test charts pasted on them.
These bozos think they're studying neurons and synapses, but they're not even doing that.
Anyways. Photography is rife with people, web sites, books, essays, and videos that try to get at photography from the bottom up. By making measurements and laying out rules of thumb, perhaps we can construct a good picture out of parts, and along the way understand how to do that as a general thing.
You might as well try to understand the human brain (and, in a way, you are). As you go along, you teach your brain to notice and approve of the Rule of Thirds. You teach your brain that when the EXIF data indicates a Zeiss lens, or a Leica body, the photograph just feels better, it has a certain je ne sais quois. You teach your brain, because brains are malleable, all about these largely invented, poorly measured, parts and bits and pieces. If everyone else were on board, it would probably work, but most non-photographers and a lot of actual photographers don't know any of this crap. They may have ruined their brains, but probably with gin.
To an extent it does work, inside your social circle. Your camera club has all been trained in the same balderdash, and so will approve of your Magic Triangle Composition shot with the Wunderkamera 5J12. The trouble is that nobody else will. The trouble is that everything you've learned is a veneer, and your animal brain still doesn't know any of that stuff, and your animal brain still doesn't much like your pictures because they're kind of shitty.
Ultimately what works is the top-down, holistic, approach. Set aside all that you know, and look. Is it good? If it looks good, it is good. By definition. If the picture looks good, the composition is good, the lens is good, the camera is good, the artist is good. If not, well, not. Reach out with your feelings, Luke.
Of course it's all a cultural construct, but by setting aside all the camera club internet forum pep your DSLR images pseudo-science, you can at least judge a picture in terms of your culture, instead of the weird alien culture of camera enthusiasts.