
Perceptual Illusions - extraterra
http://nautil.us/blog/12-mind_bending-perceptual-illusions
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chrisweekly
Here are some more good ones:

[https://www.sciencealert.com/this-3d-optical-illusion-
will-m...](https://www.sciencealert.com/this-3d-optical-illusion-will-make-
you-question-the-shape-of-known-reality-kokichi-sugihara)

... which embeds my all-time favorite ("Ambiguous Cylinder")

[https://youtu.be/oWfFco7K9v8](https://youtu.be/oWfFco7K9v8)

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Fred27
Those are particularly good examples of optical illusions. Normally these sort
of articles are disappointing, but I'd not seen many of those before. Very
tempted to order one of those mugs.

~~~
drcode
LOL, that mug may win "best illusion of 2018" but definitely would also win
"things not to bring to the office in 2018"

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btilly
I used to have a printout of [https://www.michaelbach.de/ot/mot-
snakes/index.html](https://www.michaelbach.de/ot/mot-snakes/index.html) over
my desk. People got so freaked out by a piece of paper "moving" that there
were people who literally refused to go to my desk. :-)

~~~
jpfed
I'm not clicking the link, but I'm assuming it's "rotating snakes". If other
people are like me, they may have avoided it because it literally nauseates
them.

~~~
btilly
It is. I've never heard of that reaction.

People just being freaked out was fine with me. Making them actually sick
would not have been.

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otras
I was recently investigating a CSS shadow issue that looked like an uneven
shadow across the bottom of an element that had a lighter section and a darker
section, but it turned out to be illusion #6! I had to do the color picker
method on the shadow to convince myself, and even after I had convinced myself
by drawing a single color line in between, my eyes were still fooled. Very
tricky!

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mx91
Studying electrical engineering I've learned an important concept: Everything
is relative. Ex: to measure the voltage, we need a reference to measure it
against. I think the brain works very much the same way. Every perception of
reality is processed with respect to some reference.

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poopchute
I've often described colour blindness as an optical illusion, and that
confetti illusion is exactly what I have in mind. Peanut better has a green
lid and green label which makes the slightly ambiguous brown look green. Or
the walk symbol at a cross walk - usually a light is white so I just assume
that walk symbol is also white (even though I now know it's green). Or the
statue of liberty - it's a big rock so I assume grey, even though I know it's
green. However when any of these are looked at in isolation, it's clear what
their correct colours are.

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lnx01
So, the statue of liberty isn't made of rock, it's made of Bronze, the Copper
oxidised (amongst other things) eventually leaving it a bluey-green:
[https://www.iflscience.com/chemistry/the-true-color-of-
the-s...](https://www.iflscience.com/chemistry/the-true-color-of-the-statue-
of-liberty-and-it-isnt-bluegreen/)

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torgoguys
These are great and many were new to me.

Instead of #6, the one involving moving the square from the light to dark
side, I prefer the static Checker Shadow illusion[1], using the same priciple.
The problem with involving electronics in it is that there always is suspicion
that the machine is playing the trick instead of just your visual system.

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

~~~
lisper
There are no electronics in #6. That's just a piece of paper sliding back and
forth over another piece of paper.

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graedus
These are cool. FYI some of the images are displayed at the wrong aspect
ratio. The final example in particular is pretty squished, I recommend opening
the image in its own tab.

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BearOso
I’m always annoyed by the arrow length trick. This article calls it the
“Müller-Lyer” illusion. The problem is inconsistent line caps and the joints
overlapping means that the size of the line actually is changing a little. As
a result, I’m not sure whether there’s an optical illusion involved or not,
and, if there is, this is a poor way of demonstrating it.

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jpfed
This is a timely post, considering the 2018 Best Illusion of the Year Contest
has just posted
[http://illusionoftheyear.com/cat/top-10-finalists/2018/](http://illusionoftheyear.com/cat/top-10-finalists/2018/)
.

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chrisweekly
These are awesome! I studied cognitive psych and psychobiology at UVA in the
mid 90's, and my favorite class was a seminar on perception. Illusions are a
great tool for learning how our visual system works. Also, they're really
cool.

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lanius
Seems like the human perceptual system is easily hacked. I wonder how close we
can get to an actual Snow Crash bitmap?

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samirm
whoa, turns out some people with autism, schizophrenia and transgenderism
aren't affected as much by these illusions if at all.

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howlgram
source pls?

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samirm
[http://slatestarcodex.com/2017/06/28/why-are-transgender-
peo...](http://slatestarcodex.com/2017/06/28/why-are-transgender-people-
immune-to-optical-illusions/)

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mrbonner
Still can’t subscribe to the print edition!

