/ The best optical illusion I've ever seen

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john arran - on 14 May 2017
https://twitter.com/WorldAndScience/status/863532995369721857/photo/1

Just goes to show how utterly unreliable our gut feeling can be. Even when you look at some of the detail and 'prove' to yourself what's going on, it's still hard to keep believing it when you look at the whole image again. The only way I can makes sense of the whole image is by squinting really tight.
1
Oceanrower - on 14 May 2017
In reply to john arran:

I can get the inner one. After that, it all goes a bit wrong!
john arran - on 14 May 2017
In reply to Oceanrower:

The further you walk back from the screen, the less effect it has.
Lusk - on 14 May 2017
In reply to john arran:

http://3.bp.blogspot.com/-qwnZNLS9R2o/TjMPRwJfzeI/AAAAAAAAER0/Sp2rpwsizyc/s1600/All+is+Vanity+optica...

That has always been my favourite.

There's an amusing one of a lamp if you get googling ...
Blue Straggler - on 14 May 2017
In reply to john arran:

Is it really the best optical illusion you've ever seen?
Does it beat the classic "Penrose triangle", for instance?
wilkie14c - on 14 May 2017
In reply to john arran:

looks perfectly normal to me. i'll try a gain when i'm sober though hic
Pilo - on 14 May 2017
In reply to john arran:
The twelve dots is one of the best ones for hurting your brain.
https://www.theverge.com/2016/9/12/12885574/optical-illusion-12-black-dots

Wait, I got it, all 12 at once, just for a few seconds.
Post edited at 19:13
john arran - on 14 May 2017
In reply to Blue Straggler:

> Is it really the best optical illusion you've ever seen?

In the sense that the best is usually the most recent fine example of a genre you've encountered, then yes.


> Does it beat the classic "Penrose triangle", for instance?

From the images I've just googled, I'd say yes. While the triangle is pretty cool, once I quickly figured out what was going on I could view the image for what it was, and my little brain could make sense of the illusion. Not so for my linked image, which continues to baffle me even when I know why. Pilo's 12-dots example is similarly frustrating.
alan moore - on 14 May 2017
In reply to Pilo:

Aaaaargh!
Lusk - on 14 May 2017
In reply to Pilo:

That's just dotty.
The most I can see is two.
Just got the Mrs to have a look, instantly says 12!

Eh?!
Pilo - on 14 May 2017
In reply to Lusk:
I can see all 12 also. Try again but look in a different way, I mean don't concentrate on any particular point itself but the whole picture. First you get 4 then you get the 12.
Deadeye - on 14 May 2017
In reply to john arran:

Standing back at the limit of your vision makes it clear - then walk forward and there is a very distinct point where your brain throws in the towel!

That's great - thank you
Jon Stewart - on 14 May 2017
In reply to john arran:

Optical illusions are great because they reveal a little bit of what the brain is doing to create visual perception. What we perceive has little to do with the images on the retinas: this is data that goes into an unbelievably complex (compuational?) process and the output of the process is "displayed" on the "inner screen" of our consciousness. The "inner screen" is obviously a daft analogy, after all, someone (a homonculus) would need to be watching the screen...philosophical minefield altert!

In general, the data comes in from the retina and the brain asks "what kind of object in the external would generate retinal data like that?" and with a whole lot of very well-educated guesswork, we perceive a good representation of the object that caused the retinal data. In the case of this illusion, we get the data of the angle of the squares and conclude that the most likely object to cause that retinal data is a spiral pattern, without looking too closely into whether that's actually correct (we generally only look at a small bit of the visual field at any one time - the bit hitting the macula). This illusion gives us an interesting insight into the order of processing (pattern recognition) going on. We've decided there are spirals on the basis of the detailed (macular) data - the angle of the squares - and that's overridden the data that's come from the wider field (which tells us there are concentric circles). As has been pointed out, if you can the whole image to fall on the macula by viewing from a distance, the illusion disappears.

The 12 dots illusion is a similar macular versus peripheral vision job.

What I find amazing is that considering how little data actually comes in through the eyes and how our perception is mainly guessing what is out in the world on the basis of experience, how accurate it usually is. For example it's very rare for me to think that say, there's a bit of litter blowing from the pavement into the road in front of my car only find out later that it was toddler.
Lusk - on 14 May 2017
In reply to wilkie14c:

> looks perfectly normal to me. i'll try a gain when i'm sober though hic

She looked damned hot to me last night ...
sg - on 14 May 2017
In reply to Jon Stewart:

Many long years of hard-edged evolution have honed that visual system - along with all the other 'non-thinking' parts of our existence that we give little credit to. Let's not forget that; it is indeed amazing what our bodies - and those of all other living things - do, before we start thinking about anything. We see with our central nervous systems.

My own tuppence on the matter: http://www.michaelbach.de/ot/
This website has provided starters for many of my lessons over the years. While those already referenced are indeed great, my personal faves are the Charlie Chaplin masks and the moving pink / green dots...
http://www.michaelbach.de/ot/col-lilacChaser/index.html
http://www.michaelbach.de/ot/fcs-hollowFace/index.html
(The latter is particularly compelling because there really is no cleverly crafted image - it's just a mask that your brain will never be able to see the inside of).


Pilo - on 14 May 2017
In reply to sg:

Fantastic and excellent page thanks for that. One of my favorites, the 'rotating snakes' illusion + LSD combination and things will turn out quite differently from the description and comment beneath the diagram! Good subject for an PHD study me thinks.
keith-ratcliffe on 14 May 2017
In reply to john arran:
These were all the rage about 20 yrs ago
http://www.vision3d.com/sghidden/shark.html
I had a poster of one of these which I put on the wall by my desk at work. Lots of colleagues came and looked at and most eventually got the hidden image. However one older mate tried every time he looked at it but to no avail. Eventually he retired and we went out to the pub to celebrate. He was quite merry and I jokingly said he should have one last try at the 3D picture. He wobbled up to the desk - supported himself carefully and looked at the picture - jubilation! he could see it at last - its Saturn! So what is the moral of this tale?........
Post edited at 23:12
Dan Arkle - on 14 May 2017
In reply to:

The McCollough Effect is not a normal optical illusion, but very interesting if you are into this sort of thing.

Explained by the the excellent Tom Scott.
https://www.youtube.com/watch?v=Wm8ZoVQ_OJo

https://en.wikipedia.org/wiki/McCollough_effect
john arran - on 14 May 2017
In reply to keith-ratcliffe:

> These were all the rage about 20 yrs agohttp://www.vision3d.com/sghidden/shark.html

Thanks for the link. I do remember those - of course not on computer screens because IIRC they were all the rage more like 40 years ago than 20!
keith-ratcliffe on 14 May 2017
In reply to john arran:
Oh how time passes.......
wintertree - on 14 May 2017
In reply to Pilo:

> ... twelve dots ...

Understanding the basis for this effect should be mandatory before anyone is allowed out on the roads as a pedestrian, cyclist or motorist.

Understanding it explains precisely why it's so easy to not see someone in a part of your vision you genuinely think you are looking at, when really your brain is making it up.

If everyone understood *why* it's so important to move your eyes around perhaps road users would have less blind faith in others and in themselves.
Post edited at 23:29
wercat on 15 May 2017
In reply to john arran:

I think the most striking illusion I ever experienced was on a train journey. There was a long section where there were a lot of fences or walls perpendicular to the track and so there was a repeating pattern for a minute or two or more of fences forward of me sliding away to the left of my vision till they were behind.

I turned to read my book after mindlessly watching this progression for a lengthy spell.

Amazingly, a moment after my eyes settled on the page I could see lines of text sliding sideways like the fences, alternate lines moving left and right, for some little time.

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