March 2, 2017 • 40 mins
Now you see it, now you don't — optical illusions can fool us into seeing what's not actually there. But what causes that disconnect between perception and reality? Learn all about this visual trickery in today's episode.
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Speaker 1 (00:00):
Hey, March is tripod month, my friend, and you know
what that means. Yes, that means it's time to let
people know about your favorite podcasts, just to share the
sheer joy of podcast listening. That's right, it's t r
y pod still in nascent industry. A lot of people
don't know what podcasts are and helps everybody out if
(00:20):
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who I see it? Thanksgiving once a year? Right, you
should try out this thing called a podcast. Here's what
they are. Here's a cool show you should try, and
here's how to get it. Yeah, and it doesn't have
to be our show, just any podcast you like in
general that you think someone else would like, just share it. Yeah,
So get on board the dry pod train. Welcome to
(00:44):
stuff you should know from house stuff Works dot com. Hey,
and welcome to the podcast. I'm Josh Clark, This Charles W.
Chuck Bryant, and there is well Jerry just issappure Chuck
did she she did? Oh? There she's back. David copper
(01:05):
Fields in here with us as well. Today he made
the Statue of Liberty disappear. And now Jerry Jerry as
drawn by mc escher. Oh that's nice. How do you
feel about optical illusions? I feel I feel happy about
(01:27):
optical illusions. I'm not asking Josh from the third grade,
but I feel sad about articles on optical illusions in general.
It's a it's a really difficult thing to write about,
as we're about to demonstrate, it's an even more difficult
thing to talk about. Um. But it's just I think
(01:50):
the idea that every article has to inherently describe an
optical illusion and then basically follows that discrip o shin
up with and scientists don't really know what's going on.
Here's a couple of guesses that will be fully discredited
in twenty years. It's just dissatisfying. Yeah, I mean because
we were kind of we're the kind of dudes who
(02:12):
like concrete answers or at least like really solid hypotheses.
Some of these are flimsy to me. Yeah, So we
would encourage folks if you are listening at home or work,
because you can blow off work. Let's be honest, um, like,
look look up. Some of these will describe them as
best we can, and most of them you've probably seen
(02:34):
before because as you will learn, uh many many illusions
optical illusions were were drawn and conceived many years ago,
and I have just been sort of played upon over
the years in different ways. Right. Yeah, the nineteenth century was,
like the classics, the foundation of optical illusions, which not
(02:58):
coincidentally coincided with the foundation of psychology and brain research. Um,
and optical illusions were created to kind of test the
stuff or explore this stuff, right. But yeah, most of
the stuff today are just variations on these themes. Yeah. So,
like I was saying, if you're if you're able to
just you know, kind of just google this junk as
(03:18):
we say them, and you'll go, oh that thing and chuck. Actually,
there's a website called Michael Bach dot d E okay
might yeah, which is Deutscheland Germany in the English, but
it's h M I C H A E l B
A c H dot d E. And this guy just
listed he's got links to every optical illusion you could
(03:41):
possibly imagine. So that'd be a good place to go.
Just sit there and click on his site while we're
talking about these things. Yeah, and UM, what I found
is that I get um a bit of optical illusion
fatigue when I look at too many of these things
in a row. Oh, well that should be studied. Well,
I think that. I mean, we know so little about
(04:03):
optical illusions that that is, I mean, that's kind of groundbreaking. Well,
I don't mean fatigue is in like scientifically, I just
mean like I'm tired of looking at this junk. Oh,
I see what you mean. Yeah, it just bores me
after a bit. Plus a lot of require ugly color
combinations or un unpleasant color combinations. So I think that
(04:24):
probably contributes to it too. And we should do a
We don't talk a lot about Er in this one,
but we should. He deserves his own show. Sure, you
know Escher and Geiger. Maybe we'll do a combo show
with those two. Oh yeah, oh yeah, man, that guy's
brain is beautiful. Yeah. There's a lot of cultural icon
(04:45):
biographies that are floating out there. Mr Rogers and Dr SEUs.
I know we've talked about those. So maybe we'll go
on a kick. Okay, I'm ready for some kicking. Alright,
so we were Let's go back a little bit to
the history of thinking about or study optical illusions. Right,
As with most things in the West, the basis of
(05:06):
optical illusions of the first mention of optical illusions in
the literature comes from the Greeks and Aristotle in particular. Yeah.
He uh, he probably munched on some some some weird
route and stared at a waterfall for a little while
and he said, hey, dudes, if you stare at that
(05:26):
waterfall long enough, man, and then you quickly look at
that rock, it looks like the rock is moving, right,
and then the rocks like, AREM not moving? Aristotle? But
that actually has a name, correct, Yeah, it's called the
waterfall illusion appropriately or um, what's the other word for it,
(05:50):
the motion after effect. Yeah, that's what I was looking for.
This is this is like, if this is true the
explanation for it, then I'm just disappointed with our our
brains hit. The explanation is that when we're staring at
the waterfall, are neurons tracking the movement of the water
become tired out, exhausted, yeah, overwhelmed. So when we stopped
(06:14):
looking at it and they take a break, all the
other ones that weren't at work are suddenly working over
time and making things move that aren't actually moving right.
That's a stupid explanation. Uh, I don't know how buy that.
I mean, it makes sense but I think it's stupid,
it's boring, you know, just worn out neurons. Yeah, I'm
(06:34):
tired to sit down over here. Uh yeah. And then
there was, um, if we go forward a bit in
the nineteenth century, like you were talking about, there was
that that was when people got really sort of interested
in studying these things and what was going on in
the brain, because it's sort of coincided with um, studying
(06:55):
perception and how our eyes worked, and how our eyes
worked in relation to our brain. Right. And then I
guess what some of the earliest optical illusions kind of
proved though, was this longstanding idea that it are perception
of vision. Our visual experience was based in how the
(07:18):
eyes interpreted objects. And what these early optical illusions started
to prove was, no, it's actually the brain that's getting
messed up here. And some now we're starting to get
into here at this point, like some some theories that
that makes sense to me, that I think are cool.
But what these this early study started to reveal was
(07:41):
that the brain is extremely lazy and it likes to
take shortcuts. Right, Yeah, I thought, I thought this is
actually pretty interesting. Are you talking about the lag time?
The lag time, but also, yeah, there's there's plenty of
other stuff, but the lag time seems to me to
be like one specific slice of this the general tricks
of the trade that the brain uses to cut corners. Yeah,
(08:04):
and the lag time is basically, when you know, everything
seems to happen instantaneous when you when you look at something,
your eyeballs pick it up, the neurons start firing, and
the brain tells you, you know, that's a coffee cup.
But there's just the slightest little lag and the time
it takes for that to happen. And one of the
theories with optical illusions is the brain is trying to
(08:25):
predict and that slight, slight, slight. You know, I'm not
good with small uh. Units of time is nanosecond, Jordana, Yeah, Nana,
second is definitely sure, but I think we're talking tenth
of a second, Okay, So the brain basically tries to
predict what what is should come next based on what
(08:47):
we're used to seeing in real life. Is that a
good way to say it? Yeah? And the reason they
would do this is because a tenth of a second,
something can change, like a tiger can suddenly appear. Um,
so the brain is constantly looking clues in the environment
to to predict what what is that what a tenth
of a second in the future is going to be? Like, right,
(09:08):
I think things move slow enough for us humans that
it usually works pretty well. But what this researcher Mark
Changizi says is an optical illusion. Some of the optical
illusions are actually reliable ways to trick the brain into
(09:28):
making the wrong decision about what the future is gonna hold.
One of the ones that that classically falls into this
example is um what's the one that that he talks
about where it's the It's the one with the so
that you've got two parallel lines running horizontally, just you know,
(09:50):
separated by a little amount of space, and then in
the background there's radial lines all going toward a um
the point, the vanishing point on the horizon. Right. Yes,
I can't remember the name of this one, but the
the point that Changizi makes is that the radial lines,
(10:11):
lines that radiate from a center point our brains use
as a shortcut indicator of motion, the Herring illusion. Thank you.
So these radial lines that we see tell our brain, oh,
we're moving and we're moving towards this vanishing point in
the distance. So these these horizontal lines that are in
(10:33):
the foreground are actually appear to be bent in the center,
bent outward from one another very much. So, So what
Changizi saying is that the brain is predicting since it
thinks we're moving forward towards this point and then toward
these lines that as we get closer, they have to
bend to basically allow us to enter in another way.
(10:54):
But the thing is that they're they're not moving because
it's a static image, but it's the brain being tricked
into thinking we're moving forward, changing our perspective unnecessarily. Yeah,
because the brain is used to the way we move
forward in real life. I r L right for you
kids out there, and so you know, it's a lot
of this seemed like the brain almost kind of negotiating
(11:14):
with itself. Yeah, you know, yes, but I think part
of it so that lag time one makes sense, right.
Another one that makes sense to me as far as
why the brain makes shortcuts is that when when like
the physical world is in at least three dimensions that
we interact with it in, right, but our eyes are
(11:35):
giving us two dimensional representations that the brain then has
to reconstruct into three dimensions, and it's learned to take
all sorts of neat little um, it's neat little clues
to put together a pretty good prediction of what it's
looking at. Yeah, and and it can also flip flop
(11:55):
between different two different views like the is it the
Necker cube? I love it any c K E R.
And it's it's sort of that classic cube that you
learned to draw, the one that's slightly more advanced and
than the basic cube that you first learned to draw.
It's the second cube that you learned to draw right
(12:16):
on your your What was those things that you put
on your books and people? Oh, just like yeah, homemade
book covers, right exactly. Yeah, basically a brown grocery sack
is what I used. Yeah, same here. Uh that's because
we were poor. Well plus those those things held up
oh sure yeah. Um. So you look at the Necker
(12:37):
cube and um. The fun thing about the Necker cube
is you you look at it and your brain is
able to flip back and forth between the cube basically
having two different um uh positions? Is that the best
way to say it? I keep saying that, But you
know again, these things are kind of hard to describe. Well, yeah,
it's kind of like the cube is transparent and you
can see all corners of it. Yeah, so you're rain
(13:00):
is saying, Okay, is that corner close to me or
furthest away from me? It changes perspective. Yeah, and so
thanks to UM, to the wonder machine, we can put
people in these things and UM see the neurons responsible
for the different perspectives, uh, flipping back and forth depending
(13:21):
on how we're looking at it. Yeah, exactly. Pretty helpful
at this point because you had the nineteenth century where
they started to to suss out that the ideas that
the brain was responsible for this, it was the brain
messing up. And then not a lot happened in between
then and the two thousands when f M R I
(13:42):
came into UM widespread use. And then now we're starting
to see, yeah, this the a lot of these early
theories are actually correct because we can see the neurons
responsible for them. All Right, Well, let's take a little
break here and then we're gonna come back and talk
about the Herman illusion and what the Mr I said
about that one. Okay, so the Herman Herman I'm not
(14:27):
sure how to pronounce that H E R M A
N N. The Herman Grid conceived by Ludamore Herman in
you nailed this first first name? Oh yeah, Well, it's
it's one of those classic illusions that we've all seen
and it's really simple. It's just a black and white
grid of squares, and that's the one where if you're
(14:48):
just looking at it, it looks like there's these little
gray circles, little gray dots in between where these things intersect,
and there's really nothing there though, of course when you
focus on that, it goes away. Uh. And the m
R I showed that when you're looking at an illusion
like this and others like this, um the neurons are
(15:08):
competing with one another to see the light and the dark,
and basically one set of neurons wins out over the
other and then influences the message to the other. For
what you end up perceiving, right, fairly interesting and think
it is it is And this one kind of stands
on its owner in its own class, and that it's
not really the brain that's being duped. It's because of
(15:29):
the physiology of the eyes and the light receptors in
the eyes. Right, So there are arranged so that they
are they they sense distinction, like contrast between light and dark, right,
and if they're sensing both, they create this blob. There's
spill over where um, some receptors in a single cell
(15:49):
um are getting dark and some are getting light. When
you can create these blobs in the intersection, but then
when you focus your attention on the white part the
intersection between the black squares, you're using your phobio receptors,
which have far less inhibition or spill over um, so
that the gray blob disappears. In what you see is
is white. It's actually really I read probably like four
(16:14):
different explanations of it before it started to sink in. Yeah,
it's straightforward, but it's tough to explain. I think another word. Yeah,
and uh, I totally agree. Um. And one of the
reasons we know that these neurons are sort of individually
picking things up is because in these two dudes, David
Hubil and torched In Festal, great name, you're going to
(16:39):
say that, uh, in one they won the Nobel Prize
in Physiology or Medicine because they found out that there's
actually a process and how the brain uh picks of stuff.
Up and and what the I C s. And they
found that each neuron is actually responsible for one little part,
one little detail of that pattern uh in the retinal image.
(16:59):
And so that explains why these neurons can do get
out basically on what it's seen. Yeah. So, and it's
not just like uh, like neurons competing seeing light and dark.
It's it's from what I understand the the understanding of
our brain and vision is that an individual neuron is
(17:20):
responsible for, um, say a circle, It sees circles, and
it's transmitting any circular information to the brain. Another neuron
is responsible for seeing dark, another is responsible for seeing light,
another's responsible for seeing red, another is responsible for seeing texture,
and all of this sensory information, this visual information is
(17:41):
coming to the brain all at once, and these various
brain regions responsible for vision putting it together the best
way it can. You see a red ball. And there's
a lot of cues that the brain uses that just
fascinate me. For basically what's called monocular vision. Right, so
when you are using both of your eyes, especially when
(18:03):
something's up close, you're getting two separate pictures of the
same thing, and the differences between these pictures the brain
can use to easily translate it into three dimensions, right
to to to handle things like perspective and stuff like that.
But when something's further away, um, the brain has to
use other little tricks of the trade. Right. So you've
(18:25):
got things like inner position. That's a pretty straight up
one where if one objects in front of another object,
your brain says, well, the object that's behind is further away. Yeah.
Is that is that what explains like force perspective? Yes?
In art, Yes, right, I do like force perspective stuff
I do. It's kind of cool, it's neat stuff. I
(18:46):
guess that's that's probably part of the op art movement, right, Uh, yeah,
when it was at like sixties and seventies. Yeah, it
seems like yeah. And then you know, kind of coincided
with drugs, right, not surprisingly. And then there's another one
that I hadn't heard of, called atmospheric perspective. Had you
heard of that one? I had not. So. Atmospheric perspective is, um,
(19:07):
it's basically the dust, particles in the water, vapor in
the air. The further something is a way, the more
of an effect those things have on the detail you see.
If it so your brain says, well, that's a little blurry. Uh,
that's that's a far away object. And then there's there's
plenty of other ones, but the gold standard is um
is object size. Right, that's where you um, you know
(19:32):
that roughly the size of an object, and you can
use it to compare to see whether it's it's far
away or close, depending on whether it's small or large,
or if you don't know the size of an object,
but you know two objects are identical and one is
smaller than the other, well, then you know the smaller
one is further away. So the brain is like constantly
using all of these little cues and tricks to put
(19:53):
together a conception of what it's seeing at any given
point in time. And then what what um optical allusions
are are Again these things you can produce to to
reliably trick the brain into making these wrong decisions. That
that shows its hand. It reveals how the brain functions
to take these shortcuts and the tricks that uses. Right,
(20:14):
Like a brain you think you're so smart, you're really dumb.
Look at this, and the brain says, oh, stop looking,
stop looking at those things, look at normal things. Um
kind of like sorry, I kind of like the apparent
motion ones, although I can't look at a lot of them. Um,
those are the ones where something is drawn in such
(20:38):
a way that it looks like it's moving when it's
not right. The very famous snake illusion is a great example.
And you know, this is another one of those theories
that to me is a little weak. But one of
the theories is that, um, they're these almost like unnoticeable
rapid eye movements that we make. Uh how do you
pronounce that? Yeah, no, s A C C A D
(21:02):
E s YEA CICADs the cads. I think you could
probably get away with either one. All right, Well that's
what they're called. And uh, it's it's like Pruett Taylor
Vince syndrome. You remember him. Yeah, he's a great actor,
Yeah he is. Um, so those little movements he usually
get smoothed out by the brain, so we you know,
get like a static picture. But um, what it's causing
(21:25):
in this case is perceiving motion where there was no motion.
And then the other theory on this one for apparent
motion illusions is there's just so much information going on
that uh, you know, there's just confusion. Right. I saw
one that actually combined the two that that's basically said, Um,
the the CICADs are creating the illusion of motion, but
(21:49):
what they're really doing is because the brain is being
hit with all this visual information that is just totally
doesn't make sense that we never never happen in nature
except maybe in motion. That these CICADs actually each time
your eye makes this tiny movement, it refreshes this overwhelming
um overload of information onto the brain, which creates the
(22:13):
sensation of movement. Oh yeah, pretty cool. Well, one of
the cool aspects of all of this to me is
um is the fact that once you've once you've seen
the illusion and the trick to it, you can't undo that, right,
So the brain is like a, ha, you know, I
got this one, like you know, the famous one, the
(22:35):
old lady or the or the young woman, the black
and white. It's a you know, classic illusion. And once
you you know, you can stare at and be like,
I just see the young lady or I just see
the old lady. Once you've seen both, then your brain
has like I said, it says ah, and it files
that away as prior knowledge and a little folder in
the brain and you can't undo that. So once you've
(22:58):
seen it, and you've seen the trick. You can aways
look at it and kind of make that flip in
your mind, right exactly. And it's the same thing too
with them contour less figures. Where is it a wine
goblet or is it two people's faces facing one another?
Kind of thing? Right? Oh yeah, yeah, yeah, you know
the negative space. Yeah, And apparently the trick to those
(23:18):
is you focus on the black or the white and
you see whichever one appears to be in the foreground,
because what your brain is doing is saying, um, I
need a foreground and I need a background, and then
I've got something to work with, and depending on what
it's which one it's looking at, it decides this is
the foreground or this is the background. So it's either
a wine goblet in the foreground or it's two people's
(23:41):
faces in the foreground. You know, I wonder if this
stuff if they know anything about because they didn't see
anything in the research, but if they know anything that
that this is like a brain exercise and helps you out,
like you know, playing suduco or doing word puzzles, or
if the brain is like stop looking at these, you know,
(24:03):
I don't like this I can't take anymore, you know,
or you know, like literally maybe, or if it causes
stress on the brain by by taxing it in a
way that it is not accustomed to or doesn't say
it doesn't like. Obviously the brain doesn't have a you know,
it's not a little person, but you know what I'm saying. Yeah, no,
I know what you mean. But the brain, even if
(24:24):
it's not a little person, it could still not like things. Right,
So let's take another break and then, um, I want
to tell everybody what my favorite optical illusion of all
time is. Alright, chuck, Yeah, I'm ready. Well there's two
(24:59):
one I like slightly less than the other. Okay, so
start with the second place one. Okay, I knew you
were gonna say that. I think that's a great way
to do it too. So you've got um, I don't
know the name of it. I'm sure there is a name,
but actually I think it's the contour less figure as well.
You take three circles, and you cut a pie slice
(25:21):
out of all of them, like a pac man, and
you orient those pie slices so that each one forms
what appears to be the corner of a coherent square,
and you look at it, and you're like, well, there's
a square right there with some that's overlaying four circles.
But if you stop and think about it, there's no
line whatsoever that that makes that square. It's your brain
(25:44):
exclusively filling in some suggestible information to say, well, there's
a square over a field of four circles. It's pretty
neat to me. I like that one. Uh so what's
what's number one? Um? Yeah, it's called the Addleston checkerboard. Okay,
(26:04):
surely you've seen this one, right, So I'm looking it
up as we speak. It's from the nineties. There was
an M I. T Vision researcher named Edward Addolson and um,
he created this checkerboard where on the checkerboard there's you know,
dark and light squares like a normal checkerboard, and then
there's like I think, a cylinder on the checkerboard and
it's casting a shadow. And so um, he says, look
(26:28):
at this white square and then look at this black square, um,
which is lighter, which is darker. And you say, well,
that's easy. The darker square, figure B say, is obviously
darker than figure A. And he says that's wrong, that's
absolutely wrong. Figuring and figure B are exactly the same
color and shade. Um, I'm looking at it. I've seen
(26:49):
that one for sure. The whole thing. Um, it really
really works because it takes it takes advantage of two
different um tricks that you can play on the brain,
or it takes advantage of two different shortcuts the brain makes. Right.
One is that cylinder is casting a shadow, that's putting
appears to be putting Figure A into um well into
(27:12):
a shadow. Right, So your brain automatically makes assumptions that
if something is in a shadow, it would normally be lighter,
which is in this case an incorrect assumption. It's actually
the same shade as the other one. And then the
other assumption that's making is that because that square is
surrounded by um squares of a darker color, uh, and
(27:36):
it seems and it's in a shadow, it seems to
contrast it where the other figure figure B is a
dark square surrounded by light. Uh, it seems to be
darker because of the it's surrounded, because the context of
the squares that it's surrounded by. So your brain is
using two different things, the presence of a shadow and
then the context where if something is surrounded by lighter stuff,
(27:59):
it seems darker. If something surrounded by darker stuff, it
seems lighter. UM. And that's just not always the case, obviously,
because Edward Adolson proved it's not. So you want to
know My favorite the classic Ebbing House illusion E B
B I N G H A U s uh. This
one is sort of similar, but it's not so much
(28:22):
about color, but it uses adjacent objects and a lot
of these do too. They use other things surrounding something
to trick your brain. Uh. And in this case, it's
it's the classic one. Go look it up. It's the UM.
You have two orange dots. One on the left, let's say, uh,
is surrounded by six larger gray dots, and the other
(28:44):
one on the right is surrounded by eight smaller dots.
It's very simple, that's why I love it. And the
orange dots are the same size, but they look completely
different sizes, and it's just it's so simple. And I
think this is one of the one is that UM
and too they have this contest every year, I think
for like, I don't know, it's been going on for
(29:06):
at least ten or twelve years, right, uh for new
illusions and like we said earlier. You know, a lot
of these new illusions are still just sort of riffs
on the classics. Um. But the one that won a
couple of years ago was a new version of the
ebbing House illusion where um, it's actually a video that
you have to play, so it moves. Um that the
(29:29):
outer dots they it looks like at pulsates and uh,
well it is pulsating. They get bigger and smaller, and
the orange dots stays the same, but it looks like
it's shrinking and expanding, right, So it's kind of cool.
It's just to just to play on the ebbing House illusion.
But that's that's what we were saying earlier too. It's
like it's almost like they invented all of them in
(29:50):
the nineteenth century and then now we're just able to
perfect him a little more. Yeah, pretty cool. Another thing
I thought was really neat was that there's this biological
basis that is the same for everyone on planet Earth, obviously,
but they did find there some across different cultures that
(30:11):
they didn't take the same visual cues necessarily. And the
classic Mula Layah illusion that everyone has seen, and that's
just the really simple one of two straight lines, horizontal lines, uh,
and they have arrows on the ends. On one of them,
the arrows are pointing out. On the other the arrows
(30:31):
are pointing in. And those two horizontal lines appear to
be different links. And so they did a study in
South Africa and they found that most of the European
South Africans thought, yeah, like, look at them, they're different links.
Then they showed it to like, you know, the bushmen
of South Africa, and they're like, no, dummies, they're the
same weak can't you see that? And the researchers are
(30:53):
like what yeah, and they really, I mean, they had
some theories about it. Uh. That kind of makes and
so that Western societies may be a little more used
to these things that are built in straight lines and
a little more geometrical, where the other culture might be
like just more attuned to nature where there aren't so
many straight lines. Right. And because the explanation for the
(31:16):
what was it, the Meyer the mula, the Mueller liar effect,
or optical illusion is that depending on which way the
arrow was pointing, whether at the at the end of
the line or away from the line um, the brain
is used to seeing corners right. Two walls coming together
at a ceiling make that that same kind of arrow,
(31:38):
and one that's pointing away means the point of it
is further away, so it would make the line look longer,
whereas one that's pointing inward would make it look like
the corners closest to us, right, so it would seem
like the line is shorter. But but the explanation was that, well, bushman,
have never seen two walls come together at the ceiling,
so that's why it didn't happen to them. But the
(31:58):
thing that just proved that is that, um, they trained
UH computer to to look at this stuff, and they
didn't train it on three dimensional objects, so it wasn't
familiar with walls coming together with the ceiling, and it
was fooled by it as well. So they were like, well,
we we have no idea. What's going on? Then, bushman
or magic is what they said. I wonder why so
(32:20):
many of these UH illusion UH enthusiasts seemed to be
like German and Austrian. I think I had to do.
That was where the UH largely where psychology took off. Yeah,
I guess that makes sense. I guess Escher was Dutch
buzzy but um, yeah, it seems like a lot of
(32:43):
these are like German and Austrian. Yeah. I think it
has to do with that was where the hot seat
of psychology and brain research was at the time. Interesting,
h you got anything else? Actually I do have one more.
There was um a guy named Hermann von helm Holtz.
Oh he wasn't German, right, No, nice Irish guy who's
(33:06):
from Indiana. Von Helmholtz came up with these um squares
right that are not Actually they don't have confining lines
or defining lines. They're just equal lines of squares or
lines lines equally apart that formed to the brain a square.
But ones that are horizontal seems smaller and shorter than
(33:30):
ones that are vertical, which is weird because if you
are wearing like a horizontally striped shirt, everybody's like, you
look fat in that shirt. Well, von Helmholtz, you don't.
You should actually look slimmer, which surprised me. So I
started wearing horizontal stripes as a result. You got your
Charlie brown shirt out. Yeah, because that was sort of
(33:52):
the old I don't know if it's true or not,
but they said that the New York Yankees designed their
pin stripes to make Babe Ruth look thinner. I could
totally buy that, but I don't know if that's true.
I thought they had been stripes before then. But Babe
Ruth was eating a steak while they were fitting him
for and he said, thanks for thinking of me. But
he wasn't even using silver. Is he eating it with
his hand? Yeah? And he also, um uh, blended a
(34:14):
steak into a milkshake and drank that along with his
regular steak, right, And he didn't take a cigar out
while he drank it. He just put that in the
corner of his mouth. Yeah, And it's after dinner cognac.
That's why we love Babe Ruth. Ye, you know what,
we didn't get into it all. And I don't know
if they even count as illusions or if there's something
else or those and they were a boy, they were
all the rage and the early nineties I feel like
(34:37):
were those um magic I yeah, where you stare at
the thing and all of a sudden a ship pops
out at you. If you're you know, lucky enough to
be able to see it. I know a lot of
people that would just endlessly not be able to see him,
and it would frustrate them to no end. I think,
if I remember correctly, they advised that you stare into
the middle ground. Yeah, and sort of like unFocus your eyes. Yeah,
(35:00):
I was looking those up. Um. There's a Mental Floss
article on it that was pretty brief and it made sense.
I think they were machine vision learning researchers who were like, hey,
let's make some money on the side if they start
with like a depth map of something and put it
in gray scale. And I think they make two of them,
so your eyes are getting the two different versions of it,
(35:22):
but one smaller than the other, so it really makes
it pop as far as depth goes. And then somehow
the random repeating pattern that overlays it transmits that information
to your brain unconsciously. Well, so you did look it up,
then I did. I don't know if I got it
fully right because it's it's actually kind of complex, but
(35:44):
I thought they did a pretty good I would describe me.
Could you see those? Yeah? Sometimes sometimes Yeah, I always
could see them. And that's another one of those where
once you see it you can just immediately like draw
it out. Um. And of course that's there's the one
Ethan's supply and mall Rats sort of the one joke
through that movie. It was he just stares at this
(36:05):
thing like through the whole movie and he couldn't see it.
I couldn't see it, poor guy. What a great joke,
you know, speaking of that something that's always bothered me.
Stephen King said, and one of his books or something
like that, he was talking about how you can't unsee something.
I thought you said, he's talking about Mall Rats. He was,
and he he used the Man in the moon as
an example. He's like, it's like the man in the moon.
(36:26):
Once you see it, you can't unsee it, right can
I Like, I've seen the man in the moon before
and I totally can't find him again, so you can
un see it. Stephen King is wrong? What is the
man in the moon? What are you talking about? You've
never seen the man in the moon now, so I
guess probably look it up. I think it would help
(36:47):
to see somebody else pointing it out. And then when
you see the when you look at the full moon,
you you should be able to see it. But there's
a man looking down. It's Jackie Gleeson. I don't think
are you looking it up right now? Yeah? I'd never
do that was a thing that's weird. And then the
Japanese think it's a rabbit and that the rabbit is
(37:09):
up there making mochi. Really, I don't know what other
cultures think. Those are the two I'm familiar with. Huh yeah,
so mochi. All right, if you want to know more
about optical illusions, type those words into the search bar
at how stuff works better yet, go to Michael Bach
dot d E and just have some fun. Uh. And
(37:32):
since I said d E, it's time for a listener mail.
I'm gonna call this Aussie slang. We love our and
I said Aussie. I met Aussie, right, we love our
Australian listeners. We've got a lot of them. They've long
supported the show, so we'd like to shout them out. Yeah, Australia. Uh,
he said, get eye, fellas. That's pretty good. I'm not
(37:55):
gonna read the whole thing like that, but I will
just nailed Canberra. I'm a debut a listener from down
on and I'm doing my best to get through your podcast.
I love the show and finish every show with a
smile and some new fact to tell my mates about. Anyway,
I got a quick story for you to have a
laugh at and possibly be very confused by the Other night,
my mate and I were going on a uh Marcus
(38:15):
run M A C C A S. I think we've
talked about that before, right, didn't that beer? I don't know?
Uh Fosters was us Chilian? And he goes, OHI mate,
after we've been to Macus, we can drop by the
sub grab a packet dairies and then the bottle. I'll
grab a slab of EV Studies and head back to
(38:36):
yells and get piste. Okay, so let me let me
oi mate, Hello friend, after we've been to Marcus after
I don't know what that was. Next, can we dropped
by the servo? We can go hang out with Tom Servo.
I bet you anything. A servo is like a gas station.
(38:56):
Grab a pack of dirries, Uh, get some milk and
then the bottle. Oh uh, get a bottle, grab a
slab of v B Studies, get some ribs. I think
I think that's it, uh, and head back to yours
and get pissed uh and then go to sleep. I
(39:18):
think you're right on the money. Yeah, I know you
guys don't often do request be rad If you guys
did a podcast on Aussie slang's history and meanings, mostly
because I would love to hear Chuck's Aussie accent. Oh
well yeah, granted he didn't wait, he didn't translate it
himself now, so we'll never know whether I was completely right.
Someone someone will uh. And I'd love to hear both
(39:40):
of you pronounced as much Assie slang as possible. But
also because i'd like to have facts about why I
speak the way I do. Stay rad And that is
from Liam and he said, ps, we swear a lot
down here. Uh. And if that's why you can't do
an Aussie slang podcast, I don't blame you. Well, I
swear a lot. I r L Liam, but we just
(40:03):
keep it clean for the show. That's right. Nice? Yeah,
well thanks Liam. I'm not gonna do an Australian accent
because it would hurt everyone's ears. Uh. If you want
to get in touch with us, like Liam did, you
can tweet to us. I'm at josh um Clark and
at s y s K podcast, Chuck's on Facebook dot
com slash Stuff you Should Know, and Charles W. Chuck
(40:25):
Bryant and you can send us an email to Stuff
Podcasts at how stuff works dot com, and it's always
hang out with us at her home on the web.
Stuff you Should Know dot com For more on this
and thousands of other topics. Does it How stuff works
dot com
Hey, March is tripod month, my friend, and you know
what that means. Yes, that means it's time to let
people know about your favorite podcasts, just to share the
sheer joy of podcast listening. That's right, it's t r
y pod still in nascent industry. A lot of people
don't know what podcasts are and helps everybody out if
(00:20):
you would go out and just say, hey, family member,
who I see it? Thanksgiving once a year? Right, you
should try out this thing called a podcast. Here's what
they are. Here's a cool show you should try, and
here's how to get it. Yeah, and it doesn't have
to be our show, just any podcast you like in
general that you think someone else would like, just share it. Yeah,
So get on board the dry pod train. Welcome to
(00:44):
stuff you should know from house stuff Works dot com. Hey,
and welcome to the podcast. I'm Josh Clark, This Charles W.
Chuck Bryant, and there is well Jerry just issappure Chuck
did she she did? Oh? There she's back. David copper
(01:05):
Fields in here with us as well. Today he made
the Statue of Liberty disappear. And now Jerry Jerry as
drawn by mc escher. Oh that's nice. How do you
feel about optical illusions? I feel I feel happy about
(01:27):
optical illusions. I'm not asking Josh from the third grade,
but I feel sad about articles on optical illusions in general.
It's a it's a really difficult thing to write about,
as we're about to demonstrate, it's an even more difficult
thing to talk about. Um. But it's just I think
(01:50):
the idea that every article has to inherently describe an
optical illusion and then basically follows that discrip o shin
up with and scientists don't really know what's going on.
Here's a couple of guesses that will be fully discredited
in twenty years. It's just dissatisfying. Yeah, I mean because
we were kind of we're the kind of dudes who
(02:12):
like concrete answers or at least like really solid hypotheses.
Some of these are flimsy to me. Yeah, So we
would encourage folks if you are listening at home or work,
because you can blow off work. Let's be honest, um, like,
look look up. Some of these will describe them as
best we can, and most of them you've probably seen
(02:34):
before because as you will learn, uh many many illusions
optical illusions were were drawn and conceived many years ago,
and I have just been sort of played upon over
the years in different ways. Right. Yeah, the nineteenth century was,
like the classics, the foundation of optical illusions, which not
(02:58):
coincidentally coincided with the foundation of psychology and brain research. Um,
and optical illusions were created to kind of test the
stuff or explore this stuff, right. But yeah, most of
the stuff today are just variations on these themes. Yeah. So,
like I was saying, if you're if you're able to
just you know, kind of just google this junk as
(03:18):
we say them, and you'll go, oh that thing and chuck. Actually,
there's a website called Michael Bach dot d E okay
might yeah, which is Deutscheland Germany in the English, but
it's h M I C H A E l B
A c H dot d E. And this guy just
listed he's got links to every optical illusion you could
(03:41):
possibly imagine. So that'd be a good place to go.
Just sit there and click on his site while we're
talking about these things. Yeah, and UM, what I found
is that I get um a bit of optical illusion
fatigue when I look at too many of these things
in a row. Oh, well that should be studied. Well,
I think that. I mean, we know so little about
(04:03):
optical illusions that that is, I mean, that's kind of groundbreaking. Well,
I don't mean fatigue is in like scientifically, I just
mean like I'm tired of looking at this junk. Oh,
I see what you mean. Yeah, it just bores me
after a bit. Plus a lot of require ugly color
combinations or un unpleasant color combinations. So I think that
(04:24):
probably contributes to it too. And we should do a
We don't talk a lot about Er in this one,
but we should. He deserves his own show. Sure, you
know Escher and Geiger. Maybe we'll do a combo show
with those two. Oh yeah, oh yeah, man, that guy's
brain is beautiful. Yeah. There's a lot of cultural icon
(04:45):
biographies that are floating out there. Mr Rogers and Dr SEUs.
I know we've talked about those. So maybe we'll go
on a kick. Okay, I'm ready for some kicking. Alright,
so we were Let's go back a little bit to
the history of thinking about or study optical illusions. Right,
As with most things in the West, the basis of
(05:06):
optical illusions of the first mention of optical illusions in
the literature comes from the Greeks and Aristotle in particular. Yeah.
He uh, he probably munched on some some some weird
route and stared at a waterfall for a little while
and he said, hey, dudes, if you stare at that
(05:26):
waterfall long enough, man, and then you quickly look at
that rock, it looks like the rock is moving, right,
and then the rocks like, AREM not moving? Aristotle? But
that actually has a name, correct, Yeah, it's called the
waterfall illusion appropriately or um, what's the other word for it,
(05:50):
the motion after effect. Yeah, that's what I was looking for.
This is this is like, if this is true the
explanation for it, then I'm just disappointed with our our
brains hit. The explanation is that when we're staring at
the waterfall, are neurons tracking the movement of the water
become tired out, exhausted, yeah, overwhelmed. So when we stopped
(06:14):
looking at it and they take a break, all the
other ones that weren't at work are suddenly working over
time and making things move that aren't actually moving right.
That's a stupid explanation. Uh, I don't know how buy that.
I mean, it makes sense but I think it's stupid,
it's boring, you know, just worn out neurons. Yeah, I'm
(06:34):
tired to sit down over here. Uh yeah. And then
there was, um, if we go forward a bit in
the nineteenth century, like you were talking about, there was
that that was when people got really sort of interested
in studying these things and what was going on in
the brain, because it's sort of coincided with um, studying
(06:55):
perception and how our eyes worked, and how our eyes
worked in relation to our brain. Right. And then I
guess what some of the earliest optical illusions kind of
proved though, was this longstanding idea that it are perception
of vision. Our visual experience was based in how the
(07:18):
eyes interpreted objects. And what these early optical illusions started
to prove was, no, it's actually the brain that's getting
messed up here. And some now we're starting to get
into here at this point, like some some theories that
that makes sense to me, that I think are cool.
But what these this early study started to reveal was
(07:41):
that the brain is extremely lazy and it likes to
take shortcuts. Right, Yeah, I thought, I thought this is
actually pretty interesting. Are you talking about the lag time?
The lag time, but also, yeah, there's there's plenty of
other stuff, but the lag time seems to me to
be like one specific slice of this the general tricks
of the trade that the brain uses to cut corners. Yeah,
(08:04):
and the lag time is basically, when you know, everything
seems to happen instantaneous when you when you look at something,
your eyeballs pick it up, the neurons start firing, and
the brain tells you, you know, that's a coffee cup.
But there's just the slightest little lag and the time
it takes for that to happen. And one of the
theories with optical illusions is the brain is trying to
(08:25):
predict and that slight, slight, slight. You know, I'm not
good with small uh. Units of time is nanosecond, Jordana, Yeah, Nana,
second is definitely sure, but I think we're talking tenth
of a second, Okay, So the brain basically tries to
predict what what is should come next based on what
(08:47):
we're used to seeing in real life. Is that a
good way to say it? Yeah? And the reason they
would do this is because a tenth of a second,
something can change, like a tiger can suddenly appear. Um,
so the brain is constantly looking clues in the environment
to to predict what what is that what a tenth
of a second in the future is going to be? Like, right,
(09:08):
I think things move slow enough for us humans that
it usually works pretty well. But what this researcher Mark
Changizi says is an optical illusion. Some of the optical
illusions are actually reliable ways to trick the brain into
(09:28):
making the wrong decision about what the future is gonna hold.
One of the ones that that classically falls into this
example is um what's the one that that he talks
about where it's the It's the one with the so
that you've got two parallel lines running horizontally, just you know,
(09:50):
separated by a little amount of space, and then in
the background there's radial lines all going toward a um
the point, the vanishing point on the horizon. Right. Yes,
I can't remember the name of this one, but the
the point that Changizi makes is that the radial lines,
(10:11):
lines that radiate from a center point our brains use
as a shortcut indicator of motion, the Herring illusion. Thank you.
So these radial lines that we see tell our brain, oh,
we're moving and we're moving towards this vanishing point in
the distance. So these these horizontal lines that are in
(10:33):
the foreground are actually appear to be bent in the center,
bent outward from one another very much. So, So what
Changizi saying is that the brain is predicting since it
thinks we're moving forward towards this point and then toward
these lines that as we get closer, they have to
bend to basically allow us to enter in another way.
(10:54):
But the thing is that they're they're not moving because
it's a static image, but it's the brain being tricked
into thinking we're moving forward, changing our perspective unnecessarily. Yeah,
because the brain is used to the way we move
forward in real life. I r L right for you
kids out there, and so you know, it's a lot
of this seemed like the brain almost kind of negotiating
(11:14):
with itself. Yeah, you know, yes, but I think part
of it so that lag time one makes sense, right.
Another one that makes sense to me as far as
why the brain makes shortcuts is that when when like
the physical world is in at least three dimensions that
we interact with it in, right, but our eyes are
(11:35):
giving us two dimensional representations that the brain then has
to reconstruct into three dimensions, and it's learned to take
all sorts of neat little um, it's neat little clues
to put together a pretty good prediction of what it's
looking at. Yeah, and and it can also flip flop
(11:55):
between different two different views like the is it the
Necker cube? I love it any c K E R.
And it's it's sort of that classic cube that you
learned to draw, the one that's slightly more advanced and
than the basic cube that you first learned to draw.
It's the second cube that you learned to draw right
(12:16):
on your your What was those things that you put
on your books and people? Oh, just like yeah, homemade
book covers, right exactly. Yeah, basically a brown grocery sack
is what I used. Yeah, same here. Uh that's because
we were poor. Well plus those those things held up
oh sure yeah. Um. So you look at the Necker
(12:37):
cube and um. The fun thing about the Necker cube
is you you look at it and your brain is
able to flip back and forth between the cube basically
having two different um uh positions? Is that the best
way to say it? I keep saying that, But you
know again, these things are kind of hard to describe. Well, yeah,
it's kind of like the cube is transparent and you
can see all corners of it. Yeah, so you're rain
(13:00):
is saying, Okay, is that corner close to me or
furthest away from me? It changes perspective. Yeah, and so
thanks to UM, to the wonder machine, we can put
people in these things and UM see the neurons responsible
for the different perspectives, uh, flipping back and forth depending
(13:21):
on how we're looking at it. Yeah, exactly. Pretty helpful
at this point because you had the nineteenth century where
they started to to suss out that the ideas that
the brain was responsible for this, it was the brain
messing up. And then not a lot happened in between
then and the two thousands when f M R I
(13:42):
came into UM widespread use. And then now we're starting
to see, yeah, this the a lot of these early
theories are actually correct because we can see the neurons
responsible for them. All Right, Well, let's take a little
break here and then we're gonna come back and talk
about the Herman illusion and what the Mr I said
about that one. Okay, so the Herman Herman I'm not
(14:27):
sure how to pronounce that H E R M A
N N. The Herman Grid conceived by Ludamore Herman in
you nailed this first first name? Oh yeah, Well, it's
it's one of those classic illusions that we've all seen
and it's really simple. It's just a black and white
grid of squares, and that's the one where if you're
(14:48):
just looking at it, it looks like there's these little
gray circles, little gray dots in between where these things intersect,
and there's really nothing there though, of course when you
focus on that, it goes away. Uh. And the m
R I showed that when you're looking at an illusion
like this and others like this, um the neurons are
(15:08):
competing with one another to see the light and the dark,
and basically one set of neurons wins out over the
other and then influences the message to the other. For
what you end up perceiving, right, fairly interesting and think
it is it is And this one kind of stands
on its owner in its own class, and that it's
not really the brain that's being duped. It's because of
(15:29):
the physiology of the eyes and the light receptors in
the eyes. Right, So there are arranged so that they
are they they sense distinction, like contrast between light and dark, right,
and if they're sensing both, they create this blob. There's
spill over where um, some receptors in a single cell
(15:49):
um are getting dark and some are getting light. When
you can create these blobs in the intersection, but then
when you focus your attention on the white part the
intersection between the black squares, you're using your phobio receptors,
which have far less inhibition or spill over um, so
that the gray blob disappears. In what you see is
is white. It's actually really I read probably like four
(16:14):
different explanations of it before it started to sink in. Yeah,
it's straightforward, but it's tough to explain. I think another word. Yeah,
and uh, I totally agree. Um. And one of the
reasons we know that these neurons are sort of individually
picking things up is because in these two dudes, David
Hubil and torched In Festal, great name, you're going to
(16:39):
say that, uh, in one they won the Nobel Prize
in Physiology or Medicine because they found out that there's
actually a process and how the brain uh picks of stuff.
Up and and what the I C s. And they
found that each neuron is actually responsible for one little part,
one little detail of that pattern uh in the retinal image.
(16:59):
And so that explains why these neurons can do get
out basically on what it's seen. Yeah. So, and it's
not just like uh, like neurons competing seeing light and dark.
It's it's from what I understand the the understanding of
our brain and vision is that an individual neuron is
(17:20):
responsible for, um, say a circle, It sees circles, and
it's transmitting any circular information to the brain. Another neuron
is responsible for seeing dark, another is responsible for seeing light,
another's responsible for seeing red, another is responsible for seeing texture,
and all of this sensory information, this visual information is
(17:41):
coming to the brain all at once, and these various
brain regions responsible for vision putting it together the best
way it can. You see a red ball. And there's
a lot of cues that the brain uses that just
fascinate me. For basically what's called monocular vision. Right, so
when you are using both of your eyes, especially when
(18:03):
something's up close, you're getting two separate pictures of the
same thing, and the differences between these pictures the brain
can use to easily translate it into three dimensions, right
to to to handle things like perspective and stuff like that.
But when something's further away, um, the brain has to
use other little tricks of the trade. Right. So you've
(18:25):
got things like inner position. That's a pretty straight up
one where if one objects in front of another object,
your brain says, well, the object that's behind is further away. Yeah.
Is that is that what explains like force perspective? Yes?
In art, Yes, right, I do like force perspective stuff
I do. It's kind of cool, it's neat stuff. I
(18:46):
guess that's that's probably part of the op art movement, right, Uh, yeah,
when it was at like sixties and seventies. Yeah, it
seems like yeah. And then you know, kind of coincided
with drugs, right, not surprisingly. And then there's another one
that I hadn't heard of, called atmospheric perspective. Had you
heard of that one? I had not. So. Atmospheric perspective is, um,
(19:07):
it's basically the dust, particles in the water, vapor in
the air. The further something is a way, the more
of an effect those things have on the detail you see.
If it so your brain says, well, that's a little blurry. Uh,
that's that's a far away object. And then there's there's
plenty of other ones, but the gold standard is um
is object size. Right, that's where you um, you know
(19:32):
that roughly the size of an object, and you can
use it to compare to see whether it's it's far
away or close, depending on whether it's small or large,
or if you don't know the size of an object,
but you know two objects are identical and one is
smaller than the other, well, then you know the smaller
one is further away. So the brain is like constantly
using all of these little cues and tricks to put
(19:53):
together a conception of what it's seeing at any given
point in time. And then what what um optical allusions
are are Again these things you can produce to to
reliably trick the brain into making these wrong decisions. That
that shows its hand. It reveals how the brain functions
to take these shortcuts and the tricks that uses. Right,
(20:14):
Like a brain you think you're so smart, you're really dumb.
Look at this, and the brain says, oh, stop looking,
stop looking at those things, look at normal things. Um
kind of like sorry, I kind of like the apparent
motion ones, although I can't look at a lot of them. Um,
those are the ones where something is drawn in such
(20:38):
a way that it looks like it's moving when it's
not right. The very famous snake illusion is a great example.
And you know, this is another one of those theories
that to me is a little weak. But one of
the theories is that, um, they're these almost like unnoticeable
rapid eye movements that we make. Uh how do you
pronounce that? Yeah, no, s A C C A D
(21:02):
E s YEA CICADs the cads. I think you could
probably get away with either one. All right, Well that's
what they're called. And uh, it's it's like Pruett Taylor
Vince syndrome. You remember him. Yeah, he's a great actor,
Yeah he is. Um, so those little movements he usually
get smoothed out by the brain, so we you know,
get like a static picture. But um, what it's causing
(21:25):
in this case is perceiving motion where there was no motion.
And then the other theory on this one for apparent
motion illusions is there's just so much information going on
that uh, you know, there's just confusion. Right. I saw
one that actually combined the two that that's basically said, Um,
the the CICADs are creating the illusion of motion, but
(21:49):
what they're really doing is because the brain is being
hit with all this visual information that is just totally
doesn't make sense that we never never happen in nature
except maybe in motion. That these CICADs actually each time
your eye makes this tiny movement, it refreshes this overwhelming
um overload of information onto the brain, which creates the
(22:13):
sensation of movement. Oh yeah, pretty cool. Well, one of
the cool aspects of all of this to me is
um is the fact that once you've once you've seen
the illusion and the trick to it, you can't undo that, right,
So the brain is like a, ha, you know, I
got this one, like you know, the famous one, the
(22:35):
old lady or the or the young woman, the black
and white. It's a you know, classic illusion. And once
you you know, you can stare at and be like,
I just see the young lady or I just see
the old lady. Once you've seen both, then your brain
has like I said, it says ah, and it files
that away as prior knowledge and a little folder in
the brain and you can't undo that. So once you've
(22:58):
seen it, and you've seen the trick. You can aways
look at it and kind of make that flip in
your mind, right exactly. And it's the same thing too
with them contour less figures. Where is it a wine
goblet or is it two people's faces facing one another?
Kind of thing? Right? Oh yeah, yeah, yeah, you know
the negative space. Yeah, And apparently the trick to those
(23:18):
is you focus on the black or the white and
you see whichever one appears to be in the foreground,
because what your brain is doing is saying, um, I
need a foreground and I need a background, and then
I've got something to work with, and depending on what
it's which one it's looking at, it decides this is
the foreground or this is the background. So it's either
a wine goblet in the foreground or it's two people's
(23:41):
faces in the foreground. You know, I wonder if this
stuff if they know anything about because they didn't see
anything in the research, but if they know anything that
that this is like a brain exercise and helps you out,
like you know, playing suduco or doing word puzzles, or
if the brain is like stop looking at these, you know,
(24:03):
I don't like this I can't take anymore, you know,
or you know, like literally maybe, or if it causes
stress on the brain by by taxing it in a
way that it is not accustomed to or doesn't say
it doesn't like. Obviously the brain doesn't have a you know,
it's not a little person, but you know what I'm saying. Yeah, no,
I know what you mean. But the brain, even if
(24:24):
it's not a little person, it could still not like things. Right,
So let's take another break and then, um, I want
to tell everybody what my favorite optical illusion of all
time is. Alright, chuck, Yeah, I'm ready. Well there's two
(24:59):
one I like slightly less than the other. Okay, so
start with the second place one. Okay, I knew you
were gonna say that. I think that's a great way
to do it too. So you've got um, I don't
know the name of it. I'm sure there is a name,
but actually I think it's the contour less figure as well.
You take three circles, and you cut a pie slice
(25:21):
out of all of them, like a pac man, and
you orient those pie slices so that each one forms
what appears to be the corner of a coherent square,
and you look at it, and you're like, well, there's
a square right there with some that's overlaying four circles.
But if you stop and think about it, there's no
line whatsoever that that makes that square. It's your brain
(25:44):
exclusively filling in some suggestible information to say, well, there's
a square over a field of four circles. It's pretty
neat to me. I like that one. Uh so what's
what's number one? Um? Yeah, it's called the Addleston checkerboard. Okay,
(26:04):
surely you've seen this one, right, So I'm looking it
up as we speak. It's from the nineties. There was
an M I. T Vision researcher named Edward Addolson and um,
he created this checkerboard where on the checkerboard there's you know,
dark and light squares like a normal checkerboard, and then
there's like I think, a cylinder on the checkerboard and
it's casting a shadow. And so um, he says, look
(26:28):
at this white square and then look at this black square, um,
which is lighter, which is darker. And you say, well,
that's easy. The darker square, figure B say, is obviously
darker than figure A. And he says that's wrong, that's
absolutely wrong. Figuring and figure B are exactly the same
color and shade. Um, I'm looking at it. I've seen
(26:49):
that one for sure. The whole thing. Um, it really
really works because it takes it takes advantage of two
different um tricks that you can play on the brain,
or it takes advantage of two different shortcuts the brain makes. Right.
One is that cylinder is casting a shadow, that's putting
appears to be putting Figure A into um well into
(27:12):
a shadow. Right, So your brain automatically makes assumptions that
if something is in a shadow, it would normally be lighter,
which is in this case an incorrect assumption. It's actually
the same shade as the other one. And then the
other assumption that's making is that because that square is
surrounded by um squares of a darker color, uh, and
(27:36):
it seems and it's in a shadow, it seems to
contrast it where the other figure figure B is a
dark square surrounded by light. Uh, it seems to be
darker because of the it's surrounded, because the context of
the squares that it's surrounded by. So your brain is
using two different things, the presence of a shadow and
then the context where if something is surrounded by lighter stuff,
(27:59):
it seems darker. If something surrounded by darker stuff, it
seems lighter. UM. And that's just not always the case, obviously,
because Edward Adolson proved it's not. So you want to
know My favorite the classic Ebbing House illusion E B
B I N G H A U s uh. This
one is sort of similar, but it's not so much
(28:22):
about color, but it uses adjacent objects and a lot
of these do too. They use other things surrounding something
to trick your brain. Uh. And in this case, it's
it's the classic one. Go look it up. It's the UM.
You have two orange dots. One on the left, let's say, uh,
is surrounded by six larger gray dots, and the other
(28:44):
one on the right is surrounded by eight smaller dots.
It's very simple, that's why I love it. And the
orange dots are the same size, but they look completely
different sizes, and it's just it's so simple. And I
think this is one of the one is that UM
and too they have this contest every year, I think
for like, I don't know, it's been going on for
(29:06):
at least ten or twelve years, right, uh for new
illusions and like we said earlier. You know, a lot
of these new illusions are still just sort of riffs
on the classics. Um. But the one that won a
couple of years ago was a new version of the
ebbing House illusion where um, it's actually a video that
you have to play, so it moves. Um that the
(29:29):
outer dots they it looks like at pulsates and uh,
well it is pulsating. They get bigger and smaller, and
the orange dots stays the same, but it looks like
it's shrinking and expanding, right, So it's kind of cool.
It's just to just to play on the ebbing House illusion.
But that's that's what we were saying earlier too. It's
like it's almost like they invented all of them in
(29:50):
the nineteenth century and then now we're just able to
perfect him a little more. Yeah, pretty cool. Another thing
I thought was really neat was that there's this biological
basis that is the same for everyone on planet Earth, obviously,
but they did find there some across different cultures that
(30:11):
they didn't take the same visual cues necessarily. And the
classic Mula Layah illusion that everyone has seen, and that's
just the really simple one of two straight lines, horizontal lines, uh,
and they have arrows on the ends. On one of them,
the arrows are pointing out. On the other the arrows
(30:31):
are pointing in. And those two horizontal lines appear to
be different links. And so they did a study in
South Africa and they found that most of the European
South Africans thought, yeah, like, look at them, they're different links.
Then they showed it to like, you know, the bushmen
of South Africa, and they're like, no, dummies, they're the
same weak can't you see that? And the researchers are
(30:53):
like what yeah, and they really, I mean, they had
some theories about it. Uh. That kind of makes and
so that Western societies may be a little more used
to these things that are built in straight lines and
a little more geometrical, where the other culture might be
like just more attuned to nature where there aren't so
many straight lines. Right. And because the explanation for the
(31:16):
what was it, the Meyer the mula, the Mueller liar effect,
or optical illusion is that depending on which way the
arrow was pointing, whether at the at the end of
the line or away from the line um, the brain
is used to seeing corners right. Two walls coming together
at a ceiling make that that same kind of arrow,
(31:38):
and one that's pointing away means the point of it
is further away, so it would make the line look longer,
whereas one that's pointing inward would make it look like
the corners closest to us, right, so it would seem
like the line is shorter. But but the explanation was that, well, bushman,
have never seen two walls come together at the ceiling,
so that's why it didn't happen to them. But the
(31:58):
thing that just proved that is that, um, they trained
UH computer to to look at this stuff, and they
didn't train it on three dimensional objects, so it wasn't
familiar with walls coming together with the ceiling, and it
was fooled by it as well. So they were like, well,
we we have no idea. What's going on? Then, bushman
or magic is what they said. I wonder why so
(32:20):
many of these UH illusion UH enthusiasts seemed to be
like German and Austrian. I think I had to do.
That was where the UH largely where psychology took off. Yeah,
I guess that makes sense. I guess Escher was Dutch
buzzy but um, yeah, it seems like a lot of
(32:43):
these are like German and Austrian. Yeah. I think it
has to do with that was where the hot seat
of psychology and brain research was at the time. Interesting,
h you got anything else? Actually I do have one more.
There was um a guy named Hermann von helm Holtz.
Oh he wasn't German, right, No, nice Irish guy who's
(33:06):
from Indiana. Von Helmholtz came up with these um squares
right that are not Actually they don't have confining lines
or defining lines. They're just equal lines of squares or
lines lines equally apart that formed to the brain a square.
But ones that are horizontal seems smaller and shorter than
(33:30):
ones that are vertical, which is weird because if you
are wearing like a horizontally striped shirt, everybody's like, you
look fat in that shirt. Well, von Helmholtz, you don't.
You should actually look slimmer, which surprised me. So I
started wearing horizontal stripes as a result. You got your
Charlie brown shirt out. Yeah, because that was sort of
(33:52):
the old I don't know if it's true or not,
but they said that the New York Yankees designed their
pin stripes to make Babe Ruth look thinner. I could
totally buy that, but I don't know if that's true.
I thought they had been stripes before then. But Babe
Ruth was eating a steak while they were fitting him
for and he said, thanks for thinking of me. But
he wasn't even using silver. Is he eating it with
his hand? Yeah? And he also, um uh, blended a
(34:14):
steak into a milkshake and drank that along with his
regular steak, right, And he didn't take a cigar out
while he drank it. He just put that in the
corner of his mouth. Yeah, And it's after dinner cognac.
That's why we love Babe Ruth. Ye, you know what,
we didn't get into it all. And I don't know
if they even count as illusions or if there's something
else or those and they were a boy, they were
all the rage and the early nineties I feel like
(34:37):
were those um magic I yeah, where you stare at
the thing and all of a sudden a ship pops
out at you. If you're you know, lucky enough to
be able to see it. I know a lot of
people that would just endlessly not be able to see him,
and it would frustrate them to no end. I think,
if I remember correctly, they advised that you stare into
the middle ground. Yeah, and sort of like unFocus your eyes. Yeah,
(35:00):
I was looking those up. Um. There's a Mental Floss
article on it that was pretty brief and it made sense.
I think they were machine vision learning researchers who were like, hey,
let's make some money on the side if they start
with like a depth map of something and put it
in gray scale. And I think they make two of them,
so your eyes are getting the two different versions of it,
(35:22):
but one smaller than the other, so it really makes
it pop as far as depth goes. And then somehow
the random repeating pattern that overlays it transmits that information
to your brain unconsciously. Well, so you did look it up,
then I did. I don't know if I got it
fully right because it's it's actually kind of complex, but
(35:44):
I thought they did a pretty good I would describe me.
Could you see those? Yeah? Sometimes sometimes Yeah, I always
could see them. And that's another one of those where
once you see it you can just immediately like draw
it out. Um. And of course that's there's the one
Ethan's supply and mall Rats sort of the one joke
through that movie. It was he just stares at this
(36:05):
thing like through the whole movie and he couldn't see it.
I couldn't see it, poor guy. What a great joke,
you know, speaking of that something that's always bothered me.
Stephen King said, and one of his books or something
like that, he was talking about how you can't unsee something.
I thought you said, he's talking about Mall Rats. He was,
and he he used the Man in the moon as
an example. He's like, it's like the man in the moon.
(36:26):
Once you see it, you can't unsee it, right can
I Like, I've seen the man in the moon before
and I totally can't find him again, so you can
un see it. Stephen King is wrong? What is the
man in the moon? What are you talking about? You've
never seen the man in the moon now, so I
guess probably look it up. I think it would help
(36:47):
to see somebody else pointing it out. And then when
you see the when you look at the full moon,
you you should be able to see it. But there's
a man looking down. It's Jackie Gleeson. I don't think
are you looking it up right now? Yeah? I'd never
do that was a thing that's weird. And then the
Japanese think it's a rabbit and that the rabbit is
(37:09):
up there making mochi. Really, I don't know what other
cultures think. Those are the two I'm familiar with. Huh yeah,
so mochi. All right, if you want to know more
about optical illusions, type those words into the search bar
at how stuff works better yet, go to Michael Bach
dot d E and just have some fun. Uh. And
(37:32):
since I said d E, it's time for a listener mail.
I'm gonna call this Aussie slang. We love our and
I said Aussie. I met Aussie, right, we love our
Australian listeners. We've got a lot of them. They've long
supported the show, so we'd like to shout them out. Yeah, Australia. Uh,
he said, get eye, fellas. That's pretty good. I'm not
(37:55):
gonna read the whole thing like that, but I will
just nailed Canberra. I'm a debut a listener from down
on and I'm doing my best to get through your podcast.
I love the show and finish every show with a
smile and some new fact to tell my mates about. Anyway,
I got a quick story for you to have a
laugh at and possibly be very confused by the Other night,
my mate and I were going on a uh Marcus
(38:15):
run M A C C A S. I think we've
talked about that before, right, didn't that beer? I don't know?
Uh Fosters was us Chilian? And he goes, OHI mate,
after we've been to Macus, we can drop by the
sub grab a packet dairies and then the bottle. I'll
grab a slab of EV Studies and head back to
(38:36):
yells and get piste. Okay, so let me let me
oi mate, Hello friend, after we've been to Marcus after
I don't know what that was. Next, can we dropped
by the servo? We can go hang out with Tom Servo.
I bet you anything. A servo is like a gas station.
(38:56):
Grab a pack of dirries, Uh, get some milk and
then the bottle. Oh uh, get a bottle, grab a
slab of v B Studies, get some ribs. I think
I think that's it, uh, and head back to yours
and get pissed uh and then go to sleep. I
(39:18):
think you're right on the money. Yeah, I know you
guys don't often do request be rad If you guys
did a podcast on Aussie slang's history and meanings, mostly
because I would love to hear Chuck's Aussie accent. Oh
well yeah, granted he didn't wait, he didn't translate it
himself now, so we'll never know whether I was completely right.
Someone someone will uh. And I'd love to hear both
(39:40):
of you pronounced as much Assie slang as possible. But
also because i'd like to have facts about why I
speak the way I do. Stay rad And that is
from Liam and he said, ps, we swear a lot
down here. Uh. And if that's why you can't do
an Aussie slang podcast, I don't blame you. Well, I
swear a lot. I r L Liam, but we just
(40:03):
keep it clean for the show. That's right. Nice? Yeah,
well thanks Liam. I'm not gonna do an Australian accent
because it would hurt everyone's ears. Uh. If you want
to get in touch with us, like Liam did, you
can tweet to us. I'm at josh um Clark and
at s y s K podcast, Chuck's on Facebook dot
com slash Stuff you Should Know, and Charles W. Chuck
(40:25):
Bryant and you can send us an email to Stuff
Podcasts at how stuff works dot com, and it's always
hang out with us at her home on the web.
Stuff you Should Know dot com For more on this
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