
The basic neurobiology behind the 12-dot illusion - neurosphere
https://theneurosphere.com/2016/09/17/the-basic-neurobiology-behind-the-visual-illusion-that-is-here-to-break-the-internet/
======
Sharlin
The fovea, the area of high-resolution vision in the middle of the field of
view, is surprisingly small, just a few degrees across. The resolution falls
rapidly outside the fovea [1]. A lot of the detail we perceive in the
periphery is actually the brain filling in blanks based on "cached" data.

The resolution drop could in principle be taken advantage of in computer
graphics, especially in VR applications with robust enough eye tracking [2].

[1]
[https://en.wikipedia.org/wiki/Fovea_centralis](https://en.wikipedia.org/wiki/Fovea_centralis)

[2]
[https://en.wikipedia.org/wiki/Foveated_imaging](https://en.wikipedia.org/wiki/Foveated_imaging)

~~~
Cybiote
Interesting idea about the eye-tracking for VR: offloading computation to the
brain!

I'll make a correction that while minor, makes a world of difference: filling
in the blank is more accurately understood as the brain making bayesian
inferences or predictions or best guesses about what's missing or uncertain.
The top down interaction occurring there is much more interesting than the
term caching implies.

~~~
andrepd
>filling in the blank is more accurately understood as the brain making
bayesian inferences or predictions or best guesses about what's missing or
uncertain.

Do you have any sources, or further reading, on that?

------
chakalakasp
The way the eye interfaces with the brain never ceases to amaze me. Another
fun fact is that it even has it's own error correction mechanisms, one of
which you can intentionally miscalibrate in order to see colors that aren't
there for days, weeks, and sometimes even months after doing the calibration
(which is acheived by looking at a very specific image pattern for a long
time). I would not recommend actually doing this, as those who have have
reported back that the illusory colors become quite distracting and actually
cause a bit of emotional distress after many months, but it's crazy that the
brain has this kind of chromatic abboration error correction programmed in in
the first place.
[https://en.wikipedia.org/wiki/McCollough_effect](https://en.wikipedia.org/wiki/McCollough_effect)

~~~
dahart
The color scientists who first told me about the McCollough effect adamantly
refused to ever try it, saying it could damage your vision forever.

So I was scared to try it, but eventually I did and for me the effect went
away after a couple minutes. Maybe I'm lucky, but the warnings & the legend of
the effect lasting months make such a good story, I have to wonder if it's a
little overstated.

But -- what if the effect is just as easy to unlearn somehow, as it is to
learn? It's existence may have a lot to do with gratings being pretty uncommon
in nature, leaving a weak spot in the system that is easily trainable and slow
to re-adapt just because we don't stare at gratings very often.

~~~
jacobolus
How long did you stare at the test pattern?

For long-lasting effect mis-calibrating any of these low level visual
recognizers, you need to look at the test pattern for quite a while. Just a
minute or two isn’t going to prompt a long-term effect.

~~~
dahart
Ah, you're right. That part was left out of the warnings I got. "Jones and
Holding (1975) found that 15 minutes of induction can lead to an effect
lasting 3.5 months."

I don't remember how long I tried the first time, but I'm sure it was not
longer than 2-3 minutes.

The article says an anti-McCoullough effect can override the first effect. Can
you also undo or override one ME with another ME using opposing colors?

------
kevinalexbrown
I'm not sure the central argument fully explains the illusion.

If you can simultaneously see several stars in the sky using your peripheral
vision using averted gaze, why not several dots?

I suspect uncertainty plays a part, but image completion from higher-order
feedback that complete the lines might drive the illusion more. Put another
way, I believe if you remove the gray lines, the illusion ceases to work.

~~~
takatin
Because stars in the sky is a high contrast visual. That applies here too, I
increased the contrast using Photoshop and the illusion is gone, you can see
all 12 dots perfectly fine —
[http://imgur.com/a/G4xR4](http://imgur.com/a/G4xR4) I think they are spot on,
outside the fovea, contrast detection capability of our eyes dip drastically
thereby blending the dots lying outside the fovea with the surrounding grid.
Increase the contrast to the point where even the regions outside the fovea
can detect it and the illusion goes away.

~~~
kevinalexbrown
I don't think that explains it, either: Even in low contrast, the illusion
fails w/o the lines, as far as I can tell.

~~~
taeric
Without the lines... there is much higher contrast.

I'm all for hearing an alternative hypothesis, but right now this article's
seems pretty good at covering whta is happening.

------
erelde
I found that once I zoomed in to have only 6 dots on the screen and zoomed
out, the illusion disappeared and I was able to see the 12 dots
simultaneously.

I tested it on a friend and same thing but he had to stay zoomed in longer
than me, for me it was instant, he had to stay focused 5 or 10 seconds.

And now I can't not see the 12 dots even 48 hours later without being exposed
to the image.

~~~
SomeStupidPoint
I'm replying to you rather than making another top level comment to prevent
sprawl, but I'm adding a different way the effect changed for me. (I'll
probably try yours later, when I'm done playing with it, lol)

For me, holding a "picture" of what the picture is in my head and trying to
heat map where I think my view is spotting the dots changed it from seeing
about 4 (in a triangle or box) to about 6 (in weird squiggles). I think that
actively trying to see it changes how my brain caches information as it moves
the eyes' focus.

------
dharma1
I was looking into this when the 12-dot illusion came out, and found an
interesting refutation of the receptive field theory regarding a related
illusion - the original Hermann grid. I'm not sure if it also applies to the
12-dot illusion, where the illusion seems to be more about foveal/peripheral
accuracy.

You can read about it here, and play with a demo:

[http://www.michaelbach.de/ot/lum-
herGridCurved/index.html](http://www.michaelbach.de/ot/lum-
herGridCurved/index.html)

[http://web.mit.edu/bcs/schillerlab/research/A-Vision/A15-2.h...](http://web.mit.edu/bcs/schillerlab/research/A-Vision/A15-2.htm)

~~~
joveian
Very interesting, thanks! Especially that second link.

Interestingly, I seem to have a little different effect than they did in the
second illusion they present. First of all, I find there are three distinct
perceptions, the left-right and up-down that they mention plus spinning (fan
motion). I actually didn't see the left-right form at all until getting to the
page with the larger star, although when I went back I could see it in earlier
pages. On the page with rows of red x and green o with alternating color
positions between rows, I see the top row as spinning and the other rows as
up-down; after looking at it a bit longer than for the other pages to change
it changes to all spinning, then can change back to just the top row spinning.
Now when I go back to the similar colored dots page I see the same thing,
although I didn't the first time.

Also interesting how you can affect what you see in that illusion - not
reliably at first, but with increasing accuracy over a few minutes. Or at
least affect what most of them do - that top row on some of them still does
its own thing sometimes. I wonder if more complex perception changes would be
possible with more practice. Very interesting stuff!

------
dahart
It's pretty surprising to learn how fast visual acuity falls off outside the
fovea. Our brains are amazing at making us think we can see a wide field of
view when we really can't.

This article was great, fun to read. I think this chart summarizes the whole
thing:

[https://goo.gl/images/e4JKt4](https://goo.gl/images/e4JKt4)

If you fixate on the dot in the middle, all letters are equally legible to
your eyeballs. This lets you see directly the difference in resolution between
your fovea and your peripheral vision.

------
lordnacho
I'm no expert on either field, but this neurobiology explanation sounds a lot
like what you read about in recent neural network posts:

You have some base layers taking in the physical information.

Some of those are connected in groups, somewhat like the a convolution stage
scanning a sub-area.

Sometimes, some of those areas collectively show something interesting and
pass it up. Kinda like max-pooling.

With artifical NNs, there are also images that fool the network in various
ways.

------
Roboprog
One odd thing I noticed. At the size the image displayed on my laptop, I could
look at a dot and see the dots to either side, but not the ones above or
below, even though they were the same distance apart. I guess at least my
fovea must be a horizontal ellipse, rather than a circle.

~~~
Robin_Message
I noticed the same. I wonder if this is a result of two horizontally separated
eyes (assuming too too are not a cyclops), or a training effect of reading
horizontal text regularly?

------
tomrod
This was a fascinating read about the neurobiology of the visual system. Loved
it!

------
spb
The worst trait I see when domain experts try to write "introductory" material
is a depressingly-common amnesia toward what it was like to _not already know_
their subject matter. This article is so badly written, so overly and
needlessly wordy, that I'm honestly considering deconstructing it _line-by-
line_ as a case study in how _not_ to write articles for the layman.

Here's a brief example, using the most jarring line I've been derailed by so
far (I still haven't finished reading this article, getting hung up on runs
like this):

> So what is the purpose of lateral inhibition in the retina? Let’s consider
> what kind of stimuli are optimal for activating this bipolar cell.

"What is _the purpose of lateral inhibition in the retina_?" Uh, hi - I _just
got here_. We are _zero lines_ from the place where we were first _introduced_
to _any_ of these terms (the _last two words_ of the preceding _illustration
's detail_ are literally the _first place_ the phrase "lateral inhibition"
even _appears_ ).

We've just been _shown_ this concept, _at all_ , for the first time - in a
literally _microscopic_ illustration, with some concepts so unexplained they
were just left for us to _hunt_ for ("Notice that a single neuron pools
information" \- notice _what_? Notice _how_?) - and now we're supposed to be
considering _the ultimate purpose_ for this obliquely-introduced phenomenon?
Not only that - we're supposed to be pondering this now using a _neurologist
's lexicon_?

If we were _actually supposed to be following_ what the author is saying here,
we'd be given some time to _reiterate_ this concept we were just presented
from _one angle_ , to consider it in different approaches, with descriptions
we _don 't_ immediately understand reinforcing a model we could build with
_other_ descriptions we _could_ better understand.

Instead of _reinforcing its subject_ , the article spends time on aside
paragraphs mocking what a non-neurological model of human vision might be
(talking about Dennett's Cartesian Theatre), despite the way that _nobody
reading this_ would have that misconception, and _introducing_ it only adds a
concept so unrelated that it _actively impedes understanding_ of the material.
Passages like this are just thrown in, like the author wants to say "I know
more than you, and I want you to know that I don't just know neurology, I also
took a philosophy course."

The line I excerpted _doesn 't even have to spend more time describing the
concept_. Indeed - it's actually _more effective_ if you make it _less wordy_
, because a _high-level general description_ tells us which things we _don 't
strictly have to understand_ to follow the next part. Here's how I'd write
that whole paragraph - note how much _less_ I hang meaning on unexplained
jargon:

> So, when a wide area of photoreceptors see the same signal, they actually
> _reduce_ the signal seen by the tight cluster in the center. Why reduce the
> signal like this? Because this way, when we see a _small detail_ \- one that
> _isn 't_ surrounded by a big area of the same kind of light - that wider
> group of photoreceptors (connected to the horizontal cell) _doesn 't_
> inhibit the signal. Getting stronger signals for _just the smaller details_
> is what makes stuff like dots and edges visually obvious to our human eyes.

It's not _perfectly_ clear - it still needs a round or two of editing to be
truly _smooth_ to read - but, even as a _rough_ draft, that's smoother than
anything in the linked publication, which reads like _didactic sandpaper_.

~~~
neurosphere
Bit of a harsh critique, though I appreciate reading people's comments on my
writing. Ultimately, doing some writing over the past few months has taught me
that I shouldn't necessarily underestimate people's ability to understand
scientific concepts if only I take the time to explain them properly. I'm
sorry that what I wrote wasn't sufficiently comprehensible :-( Also, I never
took a philosophy class. None of what I said was meant to be pretentious or
superior - I was just putting out there some concepts I found interesting.

~~~
spb
Yeah, don't take it personally. Most of what I wrote there was just pent-up
generalized frustration with a lot of published material out there. I regret
not sufficiently framing my post within that context.

The authors I _really_ want to hit with this kind of critique are the ones who
_aren 't_ embracing what you describe here:

> Ultimately, doing some writing over the past few months has taught me that I
> shouldn't necessarily underestimate people's ability to understand
> scientific concepts if only I take the time to explain them properly.

There's a troublingly large contingent out there that, as XKCD put it,
[communicates badly and then acts smug when it's misunderstood][1], [confused
about how communication works][2]. These are the ones I really take issue
with: the ones who are pleased when the audience who can absorb their material
is _small_ , interpreting it as _validation_ of their _own_ abilities
(thinking "I'm one of a few people who can understand this"), instead of a
_refutation_ of them.

[1]: [https://xkcd.com/169/](https://xkcd.com/169/)

[2]: [https://xkcd.com/1028/](https://xkcd.com/1028/) "Anyone who says that
they're great at communicating but 'people are bad at listening' is confused
about how communication works."

I particularly apologize for the part about it being pretentious to mention
the Cartesian Theatre. While I _would_ cut that in later drafts for being
irrelevant (which, like all irrelevant material, confuses the subject), it
really doesn't come across as anything more than that, and I was especially
projecting my frustrations from other stuff I've read when I characterized it
like that.

------
posterboy
git to the point. tenthousand lines and one of importance. to paraphrase: as
neurons are connected to form fields of perception, we can recognize shapes
quicker, but as the fields grow, we cannot resolve smaller details. I'm sure I
got some detail wrong, didn't want to copypaste.

