I came up with a few other theories, although they all have in common that the Things are trying to make us see things we do not want to see.
The Things are the bottomless Pit of Suffering that is this world. Most people frantically try to not see this, but most of those who truly comprehend go mad, either wearing themselves out with useless efforts or screaming at everyone to see the suffering. A very few are able to find peace in working ceaselessly for a better world, while knowing that their greatest efforts are but a drop of water in the ocean.
The Things are agents of those outside the Matrix who are trying to wake us all up from our illusory lives. Unlike the "nice" version depicted in "The Matrix", most people who they awaken go mad. The few who can deal with it know that the most urgent task of all is to wake everyone else up. Birds are agitated around the Things because birds are not real. They are agents of the Matrix keeping the population under surveillance, and hostile to any effort to wake us up.
The Last Judgement has already happened, and we are in Hell, a condition so intolerable that we have shut ourselves off from it in our imagination. Each one of us is the sole occupant of our imaginary world. Everyone's world is different, and different from the original, pre-Judgement world. The Things are intimations of our true condition, that we have not been able to entirely shut out. Birds are strange. Look at the bird-like figures that appear in Hieronymus Bosch's visions.
I was thinking about cats, because they fit 2 out of 3 criteria: some people can't stop sharing cat videos on social networks, and of course birds are afraid of cats. But cats usually don't kill people, only give them toxoplasmosis.
A possible explanation is that our world happens in the future long after the depicted Bird Box events; the toxoplasmosis originally drove people to suicide, but now we have adapted to it.
Birds are agitated around the Things because birds are not real.
Ha!
most of those who truly comprehend go mad,
Hm. Yeah.
A piece of advice for Price would be, notice that if you're depressed for a reason, that same reason probably applies to a lot of people, and so you can coordinate with them to make progress.
[Caveat lector: hastily written, speculative. Also banal maybe.]
[SPOILER ALERT for the film Bird Box (2018) on Netflix. IMO it's not amazing but is fairly good, possibly worth watching spoiler-free. This post will spoil most of the events of the movie. Be warned that it's a horror movie so it might be horrifying.]
Very short summary: There some Things going around, and when people look at them, they get extremely sad and kill themselves. The protagonist tries to avoid looking at the Things.
This post will discuss the question: What are the Things? What's the deal with them?
Here's some of the data to be explained:
--When someone looks at the Thing:
--Their eyes are visibly altered; the irises become jagged or marked.
--Most people:
--Their eyes tear up.
--They become extremely suicidal and kill themselves immediately if possible, including by creative means (e.g. Douglas, bound to his chair, tipping over and smashing his head on something hard).
--Some people:
--They don't kill themselves.
--They say the Thing is beautiful.
--They want others to look at the Thing.
--They say the Things will cleanse the world.
--These people include: people who were in an insane asylum, a guy who was a criminal and was "kind of weird but nice" and used others's pity for him to trick them into Looking, some people who go around looting, a guy who tries to violently force peotle to Look, and a businessman who was (he claims) forced to look and who then very deliberately treacherously forces people to Look.
--Birds get agitated when a Thing is around.
--Even just looking at a digital image of a Thing is sufficient to have the effect.
--When a Thing is around, a person may hear voices of people (especially dead people, but also live ones) they know well (perhaps, people they love or trust) calling to them, asking for help, and asking them to come closer and look at the Things.
--Kids can hear voices from the Thing, and also kill themselves if they Look.
So, the question: What's the deal with the Things? What's this about?
Vaguely, it seems like it's about inner demons, and/or about Death. Or about the unthinkable. Doug looks at a Thing through a camera and then kills himself, so the effect is mediated by the information in the Thing's appearance. It's Lovecraftian in a specific sense: it's about things that are incomprehensible because if you comprehend them you go insane. It's about Blindspots, things you don't look at, don't let yourself look at, do everything you can do to avoid looking at, that you built your life and relationships around not seeing.
One interpretation of the voices is that you can use your social embedding as a source of signposts towards seeing what you can't see yourself, what's in your meta-blindspot that you can't get out of without triangulation of the objective via the intersubjective. A different interpretation is that the voices of people you let into your soul, are attack surfaces that an adversary can use against you. Another interpretation is something to do with death, and the voices of the dead being imprinted on the living. (But in the forest the girl hears the voice of Malorie, while Malorie is alive.)
One interpretation of those who can see the Thing, is that they are being stigmatized by the narrator. Like, it's not that they can see it because they're insane or criminal, but rather that they are honest, and therefore they can see it and also society has already rejected them for being honest in general, by labeling them as insane or criminal. Another interpretation is that those who can look had already been damaged by having already seen, in a more mundane way, whatever's really behind the Things. Another interpretation is that criminals and such have already been forced to deal with whatever's in the Thing.
But it's weird that no one can both Look and also not be malicious after. It's weird that the nerd who knows all about demons can't use Reason to safely Look, and the soldier who's seen war can't look. It's weird that kids can't look. Also there should be Buddhists or similar who can Look.
What's the deal with the eyes changing? How is that implied by any of the above? Also why do birds get agitated?
Ok so things seem to fall in place more if I take the movie like this: the movie depicts what trauma seems like to a traumatized person who is deathly afraid to think about their trauma.
(This is an awkward sort of hypothesis because saying the narrator is unreliable lets you pick and choose which things you count as real vs. imagined, and it's easier to make up plausible-sounding stories about why someone might imagine something. Still, I like the hypothesis.)
To such a person, it feels like: your soul is trapped, bound up with this Thing, such that the voices of your loved ones are calling to you out of the maelstrom... But listening to them would lead to death/insanity; if you were to look at it, you'd fall apart; the life you've cobbled together on the outskirts away from the thing would be blasted apart, and it'd be unbearable and you'd kill yourself.
To me this makes sense of the eyes changing, where the other interpretations don't. It's scary to look at trauma in part because (1) you've been avoiding it in order to carry on practically, and if you remove the blinders (changing your eyes) you might lose the ability to cope; (2) since you don't yet understand the traumatic material, you'd have to generate new concepts to be able to See it, and generating new concepts feels like--and is--changing your perception, what you track about the world; (3) since, before you know how to more deeply cope with reality, Looking is in fact dangerous, the changes to your perception are judged as damage. So, it could seem like your eyes will be fucked up by Looking, and that could even be true; e.g. trying to understand adversarial situations makes your perception more keyed to evidence of adversarialness, which if you aren't careful can put your behavior into a mode that actually causes others to be more adversarial towards you.
The people who can Look are people who are forced to practically cope with their trauma; lower class people can't just float around in a fantasy. (This story makes less sense if the business man was lying about being forced to Look.) They view it as a relief to see clearly what's going on. It's common enough for people who have (supposedly at least) "processed their trauma" to go around telling other people that they really ought to also process their own trauma, sometimes even to the point of being deceptive / coercive, e.g. some meditators and such. And this presents as hostile (and is somewhat hostile) to someone who doesn't want to do that.
The traumatized person might project onto everyone else that the Thing is unbearable to look at. The movie reifies this into a world-warping Thing, which disturbs even birds. The projection denies that kids could be creative enough to deeply cope with the Thing, denies that there could be people who have healthily coped with the Thing, and denies that Reason and reflection could be used to deliberately figure out how to cope healthily.
P.S.: Doug should have fuzzed out the video, and had someone else titrate the resolution up while leading Doug in Focusing.