In Scott Alexander's Lot's of People Going Around with Mild Hallucinations All the Time, he shows that several people not currently on LSD still experience mild hallucinations commonly associated with currently taking LSD.
I would like to test to see if I could teach you how to see these mild hallucinations, regardless of experience with psychedelics. Below are 3 tests that should take 1-2 minutes to complete. If you choose to complete 1 or more of these, please comment both failed and successful attempts. Please also comment if you can already see some of these, even if you think it seems obvious.
Test 1: Visual Snow
Description: See the Visual Snow Wiki for a nice visualization on the top-right. I would describe it as "jumpy spiderwebs made out of light", similar in feel to the "black stars" people see when feeling faint (when they get up too quick).
I would say it's NOT the same experience as mental imagination or eye floaters.
[Edit: Honestly I mixed up different phenomena for "visual snow" in my description. Here's the update:
1. Visual Snow - Like a million very tiny dots. Very much like static/white noise in the wiki. More visible in low light conditions or when you're tired. I saw it for the first time this (8/12) morning in low-light conditions.
2. Patterned lines (?) - Like the geometric/kaleidoscopic shape in this picture. Doesn't have to be that consistent or patterned but is better described by "lines" than either of the other two. This is what I meant by "jumpy spiderwebs made out of light" and what I thought visual snow was.
3. Blue-sky Sprites - The picture is a nice animation (can be seen without looking at the blue sky but apparently it's more prominent in that case). Dots and wisps the size of a mm or a little bigger. Maybe 5-100 at a time vs the million in "visual snow". Resembles afterimages and the "black stars" when feeling faint.
4. (Also very possible there's more that I've missed)
]
Test: For 1 minute (click here for a 1 minute timer), close your eyes and try to see the back of your eyelids using your peripheral vision. If a minute elapses with nothing resembling "visual snow", then it's a failure.
If it's a success, then try to see visual snow with your eyes open, again for 1 minute at most.
Test 2: Afterimage Around Objects
Description: It's similar in feel to the image on the right in the afterimage wiki. Similar to seeing a bright light and still seeing it in your vision after you look away.
Test: For 2 minutes max (click here for a 2 minute timer), find a brightly colored object that's against a different flat colored background (a red towel hanging in front of a light tan wall, your face in the mirror in front of a white door, etc), and just stare at the object using your peripheral vision. Don't shift your eyes, just pick a spot and focus on your peripheral vision. If you don't see a colored afterimage of the object around parts of that object, then it's a failure.
Test 3: Breathing Walls
Description: It looks like the static surface you're looking at (floors, walls, ceilings) is shifting, rotating, swirling, "breathing" (sort of dilating back and forth?) even though you know that it's actually still static. Usually more apparent in patterned surfaces than plain colored ones.
Test: For 1 minute, find a larger, textured surface (carpet, pop-corn ceilings, [other examples?]), and stare at it using your peripheral vision. If after a minute of staring you don't see any moving, shifting, etc, then it's a failure.
On my neurotype
This question is a bit complicated.
I have no currently diagnosed irregularities, but I did have an ADHD (Primarily Inattentive) as a teen. I was on medication for a while, then stopped taking it in college when I noticed it wasn't really helping anymore. In hindsight, I wonder if the issue in highschool was really stress combined with chronic sleep deprivation. Make of that what you will.
I do get surprised looks from doctors all the time, tho. They seem frequently startled at how in tune I am with my body and senses, so I take that as a bit irregular.
I've never used any hallucinogens.
On my meditative practice
I've been practicing vipassana and shamatha meditation for about two years now. I tend to agree that especially vipassana meditation, which is all about noticing the bare reality of the senses, would make one more likely to notice visual snow and the like if the effects are, indeed, present in most/all experiences.
That said, I have been aware of all three effects (and more) since I was a child, long before I began meditating.
On visual snow
I've known about the staticky lights or colors visible in the darker places for as long as I can remember. At this moment, I can also detect the snow in my visual field in full daylight with eyes open. I recall asking about it as a child, but in the absence of the internet my research capacity was limited. At the time, the answer I got was "yeah, that's a thing". I came to assume that visual snow was somehow related to the lights I see when gently pressing on the eye. Later, I seem to remember hearing something about cosmic rays or some such. Giving it a quick think just now, I wonder if the phenomenon occurrs in the eye or the brain. Both are consistent with your low-level sensory processing theory.
On afterimages
Likewise, I've long been aware of the glowing outlines that can appear when the eyes rest on a place for some time. They are more likely to show up in high-contrast areas of the visual field, and I'm pretty sure they are afterimages revealed by the involuntary movements of the eye.
On breathing walls
I've noticed this one forever, too. Usually this happens when I'm staring at the ceiling for whatever reason and I notice a sort of rocking, drifting tendency in the image. Like the afterimage glow, I think this has to do with involuntary eye movements. I seem to recall an experiment where people are placed in a dark room with a bright dot projected on an otherwise reference-free visual plane. Those people will consistently report the dot drifting around despite its lack of actual motion.
Similar effects