Comment by exikyut | Hacker News Reader

Comment by exikyut | Hacker News Reader

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It doesn't quite land the same way to have to explain it long-form, but...

I remember learning years ago about an experiment some researchers did where they anesthetized some test subjects' eye muscles (don't remember how), bolted them into a frame so their heads couldn't move, and positioned mirrors above that could be moved with a handle.

What this test setup found was that as long as the mirrors were constantly moving (even just a tiny bit), the participants could generally speaking see completely normally. But as soon as the mirrors stopped moving, the participants reported that their vision fairly rapidly went completely grey.

(The ba-dum-tss here is the "completely reliable" in your comment... :D)

I don't think the optic system in the brain is the only aspect that is "change-stimulated". A bit of a pet theory is that a lot of thought processes are quite similar at the low (and not so low) level.

I'm hoping to come across that study at some point, just not sure what to Google.

https://en.wikipedia.org/wiki/Troxler%27s_fading

But my favourite one of these when your vision of something doesn't go away--viewing these test images for a few minutes can alter your visual perception involuntarily for months: https://en.wikipedia.org/wiki/McCollough_effect

Edit: this might be your study, https://doi.org/10.1016/0042-6989(76)90082-1

Edit:

wtf, I didn't know that waking total paralysis was something that's experimented on in humans. It's impossible to search for too, being camouflaged completely by sleep paralysis.

> Before the succinylcholine was administered an arterial tourniquet was placed on the right arm, thus preventing local blood flow and paralysis. This procedure made it possible for JKS to communicate by flexing his hand even during total paralysis.

They found lots of other weird effects when trying to move one's eyes that are partially or fully paralysed, like feeling that the entire world is moving in the wrong direction, being able to see during saccades, and afterwards consciously perceiving an object as being in one direction but reaching somewhere entirely different when trying to touch it.

Wow, thanks for finding that PDF! I would not have had the first clue where to start.

In the Fading section on page 5 there's actually a reference to "An Active Feedback System for Stabilizing Visual Images" (1975, DOI 10.1109/TBME.1972.324155), and going and reading *that* is actually making me question my memory of what I originally took note of - I remember a bit about mirrors, I think there might have been a mention of a person's head being secured, and the part with the handles was my own conjecture (I (again) think that the setup described that the mirrors were moved, but I'm not 100% sure). I'm wondering if this was the study that was being referenced??

Thanks! The linked paper and the reference paper are both extremely interesting *adds to collection*

And it makes total sense that local anesthetic would be used to achieve paralysis, that's one brute force method lol

Troxler's fading is infuriatingly annoying (mumbled in biology's general direction), like the "L R" blind-spot test; while I think need to go stare at the McCollough effect for a bit longer, the test pattern was ever so faintly blue O.o

Here's one from 2011- no mirrors in their method, but they cite a range of other relevant studies

Visual experiences during paralysis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3232712

(What was that "humor-related task not presented here"? Why even mention it, and in the abstract too? Studying jokes so bad that they had to paralyse their subjects to tell them?)

Ah, the seventies.

> an arterial tourniquet was placed on the right arm, thus preventing local blood flow and paralysis

Don't cells begin to die off in seconds after blood flow stops? Did the researchers wire up an infusion to the arm?

You can do this any time. Just look at one point for a minute or two. It doesn't take very long to set in. I discovered this by myself back in primary school (christ, imagine how boring the lessons must have been).

It's somewhat difficult to avoid moving your gaze involuntarily, but it's ok if your eyes saccade just a tiny bit once in a while, the effect will still work.

Another interesting thing is that while everything fades to gray, if you offset your vision by a tiny bit, you'll see this weird emboss effect, where edges of objects are strengthened. It's hard to explain, but it somehow kinda makes sense to me in terms of an image transformation:

inputImage - troxlersFadingOffset = gray

inputImageWithTranslation - troxlersFadingOffset = edgeDetection

I can confirm this as well, discovered in a similar way. For me I notice objects start to fade into grey in the periphery. Another cool thing is that blinking seems to reset it for just a second or so and then things fade back to grey instantly.

> if you offset your vision by a tiny bit, you'll see this weird emboss effect, where edges of objects are strengthened.

That sounds like an FFMPEG stream with dropped keyframes, where you see a solid image then you see the changed parts of the next scene start moving but only the changed parts. It's the same mechanism in a way.

I've spent time staring as still as I can at things and tthis never happened for me. All I get is pulsating and artifacts like floating "invisible lines"

That sounds like a terrifying experiment!

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