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How Optical Illusions Work · Stuff You Should Know

0:00
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Speaker 1: So get on board the dry pod train. Welcome to
0:44
Speaker 1: stuff you should know from house stuff Works dot com. Hey,
0:53
Speaker 1: and welcome to the podcast. I'm Josh Clark, This Charles W.
0:57
Speaker 1: Chuck Bryant, and there is well Jerry just issappure Chuck
1:01
Speaker 1: did she she did? Oh? There she's back. David copper
1:05
Speaker 1: Fields in here with us as well. Today he made
1:08
Speaker 1: the Statue of Liberty disappear. And now Jerry Jerry as
1:12
Speaker 1: drawn by mc escher. Oh that's nice. How do you
1:17
Speaker 1: feel about optical illusions? I feel I feel happy about
1:27
Speaker 1: optical illusions. I'm not asking Josh from the third grade,
1:31
Speaker 1: but I feel sad about articles on optical illusions in general.
1:39
Speaker 1: It's a it's a really difficult thing to write about,
1:42
Speaker 1: as we're about to demonstrate, it's an even more difficult
1:45
Speaker 1: thing to talk about. Um. But it's just I think
1:50
Speaker 1: the idea that every article has to inherently describe an
1:55
Speaker 1: optical illusion and then basically follows that discrip o shin
2:00
Speaker 1: up with and scientists don't really know what's going on.
2:03
Speaker 1: Here's a couple of guesses that will be fully discredited
2:06
Speaker 1: in twenty years. It's just dissatisfying. Yeah, I mean because
2:10
Speaker 1: we were kind of we're the kind of dudes who
2:12
Speaker 1: like concrete answers or at least like really solid hypotheses.
2:17
Speaker 1: Some of these are flimsy to me. Yeah, So we
2:21
Speaker 1: would encourage folks if you are listening at home or work,
2:26
Speaker 1: because you can blow off work. Let's be honest, um, like,
2:30
Speaker 1: look look up. Some of these will describe them as
2:32
Speaker 1: best we can, and most of them you've probably seen
2:34
Speaker 1: before because as you will learn, uh many many illusions
2:40
Speaker 1: optical illusions were were drawn and conceived many years ago,
2:46
Speaker 1: and I have just been sort of played upon over
2:49
Speaker 1: the years in different ways. Right. Yeah, the nineteenth century was,
2:52
Speaker 1: like the classics, the foundation of optical illusions, which not
2:58
Speaker 1: coincidentally coincided with the foundation of psychology and brain research. Um,
3:04
Speaker 1: and optical illusions were created to kind of test the
3:06
Speaker 1: stuff or explore this stuff, right. But yeah, most of
3:09
Speaker 1: the stuff today are just variations on these themes. Yeah. So,
3:13
Speaker 1: like I was saying, if you're if you're able to
3:15
Speaker 1: just you know, kind of just google this junk as
3:18
Speaker 1: we say them, and you'll go, oh that thing and chuck. Actually,
3:21
Speaker 1: there's a website called Michael Bach dot d E okay
3:27
Speaker 1: might yeah, which is Deutscheland Germany in the English, but
3:32
Speaker 1: it's h M I C H A E l B
3:35
Speaker 1: A c H dot d E. And this guy just
3:37
Speaker 1: listed he's got links to every optical illusion you could
3:41
Speaker 1: possibly imagine. So that'd be a good place to go.
3:43
Speaker 1: Just sit there and click on his site while we're
3:46
Speaker 1: talking about these things. Yeah, and UM, what I found
3:50
Speaker 1: is that I get um a bit of optical illusion
3:53
Speaker 1: fatigue when I look at too many of these things
3:56
Speaker 1: in a row. Oh, well that should be studied. Well,
4:00
Speaker 1: I think that. I mean, we know so little about
4:03
Speaker 1: optical illusions that that is, I mean, that's kind of groundbreaking. Well,
4:08
Speaker 1: I don't mean fatigue is in like scientifically, I just
4:11
Speaker 1: mean like I'm tired of looking at this junk. Oh,
4:14
Speaker 1: I see what you mean. Yeah, it just bores me
4:16
Speaker 1: after a bit. Plus a lot of require ugly color
4:20
Speaker 1: combinations or un unpleasant color combinations. So I think that
4:24
Speaker 1: probably contributes to it too. And we should do a
4:29
Speaker 1: We don't talk a lot about Er in this one,
4:30
Speaker 1: but we should. He deserves his own show. Sure, you
4:33
Speaker 1: know Escher and Geiger. Maybe we'll do a combo show
4:36
Speaker 1: with those two. Oh yeah, oh yeah, man, that guy's
4:40
Speaker 1: brain is beautiful. Yeah. There's a lot of cultural icon
4:45
Speaker 1: biographies that are floating out there. Mr Rogers and Dr SEUs.
4:48
Speaker 1: I know we've talked about those. So maybe we'll go
4:50
Speaker 1: on a kick. Okay, I'm ready for some kicking. Alright,
4:55
Speaker 1: so we were Let's go back a little bit to
4:57
Speaker 1: the history of thinking about or study optical illusions. Right,
5:02
Speaker 1: As with most things in the West, the basis of
5:06
Speaker 1: optical illusions of the first mention of optical illusions in
5:09
Speaker 1: the literature comes from the Greeks and Aristotle in particular. Yeah.
5:13
Speaker 1: He uh, he probably munched on some some some weird
5:18
Speaker 1: route and stared at a waterfall for a little while
5:23
Speaker 1: and he said, hey, dudes, if you stare at that
5:26
Speaker 1: waterfall long enough, man, and then you quickly look at
5:29
Speaker 1: that rock, it looks like the rock is moving, right,
5:34
Speaker 1: and then the rocks like, AREM not moving? Aristotle? But
5:40
Speaker 1: that actually has a name, correct, Yeah, it's called the
5:44
Speaker 1: waterfall illusion appropriately or um, what's the other word for it,
5:50
Speaker 1: the motion after effect. Yeah, that's what I was looking for.
5:53
Speaker 1: This is this is like, if this is true the
5:57
Speaker 1: explanation for it, then I'm just disappointed with our our
6:00
Speaker 1: brains hit. The explanation is that when we're staring at
6:04
Speaker 1: the waterfall, are neurons tracking the movement of the water
6:08
Speaker 1: become tired out, exhausted, yeah, overwhelmed. So when we stopped
6:14
Speaker 1: looking at it and they take a break, all the
6:16
Speaker 1: other ones that weren't at work are suddenly working over
6:19
Speaker 1: time and making things move that aren't actually moving right.
6:23
Speaker 1: That's a stupid explanation. Uh, I don't know how buy that.
6:29
Speaker 1: I mean, it makes sense but I think it's stupid,
6:31
Speaker 1: it's boring, you know, just worn out neurons. Yeah, I'm
6:34
Speaker 1: tired to sit down over here. Uh yeah. And then
6:38
Speaker 1: there was, um, if we go forward a bit in
6:40
Speaker 1: the nineteenth century, like you were talking about, there was
6:44
Speaker 1: that that was when people got really sort of interested
6:47
Speaker 1: in studying these things and what was going on in
6:51
Speaker 1: the brain, because it's sort of coincided with um, studying
6:55
Speaker 1: perception and how our eyes worked, and how our eyes
7:00
Speaker 1: worked in relation to our brain. Right. And then I
7:04
Speaker 1: guess what some of the earliest optical illusions kind of
7:08
Speaker 1: proved though, was this longstanding idea that it are perception
7:14
Speaker 1: of vision. Our visual experience was based in how the
7:18
Speaker 1: eyes interpreted objects. And what these early optical illusions started
7:24
Speaker 1: to prove was, no, it's actually the brain that's getting
7:28
Speaker 1: messed up here. And some now we're starting to get
7:32
Speaker 1: into here at this point, like some some theories that
7:35
Speaker 1: that makes sense to me, that I think are cool.
7:37
Speaker 1: But what these this early study started to reveal was
7:41
Speaker 1: that the brain is extremely lazy and it likes to
7:45
Speaker 1: take shortcuts. Right, Yeah, I thought, I thought this is
7:49
Speaker 1: actually pretty interesting. Are you talking about the lag time?
7:51
Speaker 1: The lag time, but also, yeah, there's there's plenty of
7:54
Speaker 1: other stuff, but the lag time seems to me to
7:56
Speaker 1: be like one specific slice of this the general tricks
8:01
Speaker 1: of the trade that the brain uses to cut corners. Yeah,
8:04
Speaker 1: and the lag time is basically, when you know, everything
8:07
Speaker 1: seems to happen instantaneous when you when you look at something,
8:10
Speaker 1: your eyeballs pick it up, the neurons start firing, and
8:13
Speaker 1: the brain tells you, you know, that's a coffee cup.
8:16
Speaker 1: But there's just the slightest little lag and the time
8:19
Speaker 1: it takes for that to happen. And one of the
8:22
Speaker 1: theories with optical illusions is the brain is trying to
8:25
Speaker 1: predict and that slight, slight, slight. You know, I'm not
8:30
Speaker 1: good with small uh. Units of time is nanosecond, Jordana, Yeah, Nana,
8:37
Speaker 1: second is definitely sure, but I think we're talking tenth
8:39
Speaker 1: of a second, Okay, So the brain basically tries to
8:42
Speaker 1: predict what what is should come next based on what
8:47
Speaker 1: we're used to seeing in real life. Is that a
8:49
Speaker 1: good way to say it? Yeah? And the reason they
8:52
Speaker 1: would do this is because a tenth of a second,
8:54
Speaker 1: something can change, like a tiger can suddenly appear. Um,
8:58
Speaker 1: so the brain is constantly looking clues in the environment
9:01
Speaker 1: to to predict what what is that what a tenth
9:05
Speaker 1: of a second in the future is going to be? Like, right,
9:08
Speaker 1: I think things move slow enough for us humans that
9:12
Speaker 1: it usually works pretty well. But what this researcher Mark
9:17
Speaker 1: Changizi says is an optical illusion. Some of the optical
9:22
Speaker 1: illusions are actually reliable ways to trick the brain into
9:28
Speaker 1: making the wrong decision about what the future is gonna hold.
9:32
Speaker 1: One of the ones that that classically falls into this
9:35
Speaker 1: example is um what's the one that that he talks
9:40
Speaker 1: about where it's the It's the one with the so
9:44
Speaker 1: that you've got two parallel lines running horizontally, just you know,
9:50
Speaker 1: separated by a little amount of space, and then in
9:53
Speaker 1: the background there's radial lines all going toward a um
9:59
Speaker 1: the point, the vanishing point on the horizon. Right. Yes,
10:03
Speaker 1: I can't remember the name of this one, but the
10:06
Speaker 1: the point that Changizi makes is that the radial lines,
10:11
Speaker 1: lines that radiate from a center point our brains use
10:14
Speaker 1: as a shortcut indicator of motion, the Herring illusion. Thank you.
10:22
Speaker 1: So these radial lines that we see tell our brain, oh,
10:26
Speaker 1: we're moving and we're moving towards this vanishing point in
10:29
Speaker 1: the distance. So these these horizontal lines that are in
10:33
Speaker 1: the foreground are actually appear to be bent in the center,
10:37
Speaker 1: bent outward from one another very much. So, So what
10:41
Speaker 1: Changizi saying is that the brain is predicting since it
10:44
Speaker 1: thinks we're moving forward towards this point and then toward
10:47
Speaker 1: these lines that as we get closer, they have to
10:49
Speaker 1: bend to basically allow us to enter in another way.
10:54
Speaker 1: But the thing is that they're they're not moving because
10:56
Speaker 1: it's a static image, but it's the brain being tricked
10:58
Speaker 1: into thinking we're moving forward, changing our perspective unnecessarily. Yeah,
11:03
Speaker 1: because the brain is used to the way we move
11:05
Speaker 1: forward in real life. I r L right for you
11:09
Speaker 1: kids out there, and so you know, it's a lot
11:12
Speaker 1: of this seemed like the brain almost kind of negotiating
11:14
Speaker 1: with itself. Yeah, you know, yes, but I think part
11:18
Speaker 1: of it so that lag time one makes sense, right.
11:22
Speaker 1: Another one that makes sense to me as far as
11:24
Speaker 1: why the brain makes shortcuts is that when when like
11:28
Speaker 1: the physical world is in at least three dimensions that
11:31
Speaker 1: we interact with it in, right, but our eyes are
11:35
Speaker 1: giving us two dimensional representations that the brain then has
11:38
Speaker 1: to reconstruct into three dimensions, and it's learned to take
11:43
Speaker 1: all sorts of neat little um, it's neat little clues
11:48
Speaker 1: to put together a pretty good prediction of what it's
11:51
Speaker 1: looking at. Yeah, and and it can also flip flop
11:55
Speaker 1: between different two different views like the is it the
11:58
Speaker 1: Necker cube? I love it any c K E R.
12:03
Speaker 1: And it's it's sort of that classic cube that you
12:06
Speaker 1: learned to draw, the one that's slightly more advanced and
12:10
Speaker 1: than the basic cube that you first learned to draw.
12:13
Speaker 1: It's the second cube that you learned to draw right
12:16
Speaker 1: on your your What was those things that you put
12:19
Speaker 1: on your books and people? Oh, just like yeah, homemade
12:22
Speaker 1: book covers, right exactly. Yeah, basically a brown grocery sack
12:26
Speaker 1: is what I used. Yeah, same here. Uh that's because
12:29
Speaker 1: we were poor. Well plus those those things held up
12:34
Speaker 1: oh sure yeah. Um. So you look at the Necker
12:37
Speaker 1: cube and um. The fun thing about the Necker cube
12:40
Speaker 1: is you you look at it and your brain is
12:42
Speaker 1: able to flip back and forth between the cube basically
12:45
Speaker 1: having two different um uh positions? Is that the best
12:49
Speaker 1: way to say it? I keep saying that, But you
12:51
Speaker 1: know again, these things are kind of hard to describe. Well, yeah,
12:54
Speaker 1: it's kind of like the cube is transparent and you
12:57
Speaker 1: can see all corners of it. Yeah, so you're rain
13:00
Speaker 1: is saying, Okay, is that corner close to me or
13:03
Speaker 1: furthest away from me? It changes perspective. Yeah, and so
13:08
Speaker 1: thanks to UM, to the wonder machine, we can put
13:12
Speaker 1: people in these things and UM see the neurons responsible
13:17
Speaker 1: for the different perspectives, uh, flipping back and forth depending
13:21
Speaker 1: on how we're looking at it. Yeah, exactly. Pretty helpful
13:26
Speaker 1: at this point because you had the nineteenth century where
13:29
Speaker 1: they started to to suss out that the ideas that
13:32
Speaker 1: the brain was responsible for this, it was the brain
13:35
Speaker 1: messing up. And then not a lot happened in between
13:39
Speaker 1: then and the two thousands when f M R I
13:42
Speaker 1: came into UM widespread use. And then now we're starting
13:45
Speaker 1: to see, yeah, this the a lot of these early
13:49
Speaker 1: theories are actually correct because we can see the neurons
13:51
Speaker 1: responsible for them. All Right, Well, let's take a little
13:54
Speaker 1: break here and then we're gonna come back and talk
13:57
Speaker 1: about the Herman illusion and what the Mr I said
14:00
Speaker 1: about that one. Okay, so the Herman Herman I'm not
14:27
Speaker 1: sure how to pronounce that H E R M A
14:30
Speaker 1: N N. The Herman Grid conceived by Ludamore Herman in
14:35
Speaker 1: you nailed this first first name? Oh yeah, Well, it's
14:38
Speaker 1: it's one of those classic illusions that we've all seen
14:41
Speaker 1: and it's really simple. It's just a black and white
14:44
Speaker 1: grid of squares, and that's the one where if you're
14:48
Speaker 1: just looking at it, it looks like there's these little
14:50
Speaker 1: gray circles, little gray dots in between where these things intersect,
14:56
Speaker 1: and there's really nothing there though, of course when you
14:58
Speaker 1: focus on that, it goes away. Uh. And the m
15:01
Speaker 1: R I showed that when you're looking at an illusion
15:03
Speaker 1: like this and others like this, um the neurons are
15:08
Speaker 1: competing with one another to see the light and the dark,
15:11
Speaker 1: and basically one set of neurons wins out over the
15:15
Speaker 1: other and then influences the message to the other. For
15:18
Speaker 1: what you end up perceiving, right, fairly interesting and think
15:21
Speaker 1: it is it is And this one kind of stands
15:23
Speaker 1: on its owner in its own class, and that it's
15:26
Speaker 1: not really the brain that's being duped. It's because of
15:29
Speaker 1: the physiology of the eyes and the light receptors in
15:31
Speaker 1: the eyes. Right, So there are arranged so that they
15:35
Speaker 1: are they they sense distinction, like contrast between light and dark, right,
15:40
Speaker 1: and if they're sensing both, they create this blob. There's
15:44
Speaker 1: spill over where um, some receptors in a single cell
15:49
Speaker 1: um are getting dark and some are getting light. When
15:52
Speaker 1: you can create these blobs in the intersection, but then
15:55
Speaker 1: when you focus your attention on the white part the
15:57
Speaker 1: intersection between the black squares, you're using your phobio receptors,
16:02
Speaker 1: which have far less inhibition or spill over um, so
16:06
Speaker 1: that the gray blob disappears. In what you see is
16:09
Speaker 1: is white. It's actually really I read probably like four
16:14
Speaker 1: different explanations of it before it started to sink in. Yeah,
16:18
Speaker 1: it's straightforward, but it's tough to explain. I think another word. Yeah,
16:22
Speaker 1: and uh, I totally agree. Um. And one of the
16:24
Speaker 1: reasons we know that these neurons are sort of individually
16:29
Speaker 1: picking things up is because in these two dudes, David
16:33
Speaker 1: Hubil and torched In Festal, great name, you're going to
16:39
Speaker 1: say that, uh, in one they won the Nobel Prize
16:42
Speaker 1: in Physiology or Medicine because they found out that there's
16:46
Speaker 1: actually a process and how the brain uh picks of stuff.
16:50
Speaker 1: Up and and what the I C s. And they
16:51
Speaker 1: found that each neuron is actually responsible for one little part,
16:55
Speaker 1: one little detail of that pattern uh in the retinal image.
16:59
Speaker 1: And so that explains why these neurons can do get
17:03
Speaker 1: out basically on what it's seen. Yeah. So, and it's
17:07
Speaker 1: not just like uh, like neurons competing seeing light and dark.
17:11
Speaker 1: It's it's from what I understand the the understanding of
17:16
Speaker 1: our brain and vision is that an individual neuron is
17:20
Speaker 1: responsible for, um, say a circle, It sees circles, and
17:26
Speaker 1: it's transmitting any circular information to the brain. Another neuron
17:30
Speaker 1: is responsible for seeing dark, another is responsible for seeing light,
17:33
Speaker 1: another's responsible for seeing red, another is responsible for seeing texture,
17:37
Speaker 1: and all of this sensory information, this visual information is
17:41
Speaker 1: coming to the brain all at once, and these various
17:44
Speaker 1: brain regions responsible for vision putting it together the best
17:48
Speaker 1: way it can. You see a red ball. And there's
17:52
Speaker 1: a lot of cues that the brain uses that just
17:55
Speaker 1: fascinate me. For basically what's called monocular vision. Right, so
18:01
Speaker 1: when you are using both of your eyes, especially when
18:03
Speaker 1: something's up close, you're getting two separate pictures of the
18:07
Speaker 1: same thing, and the differences between these pictures the brain
18:11
Speaker 1: can use to easily translate it into three dimensions, right
18:14
Speaker 1: to to to handle things like perspective and stuff like that.
18:18
Speaker 1: But when something's further away, um, the brain has to
18:21
Speaker 1: use other little tricks of the trade. Right. So you've
18:25
Speaker 1: got things like inner position. That's a pretty straight up
18:27
Speaker 1: one where if one objects in front of another object,
18:32
Speaker 1: your brain says, well, the object that's behind is further away. Yeah.
18:36
Speaker 1: Is that is that what explains like force perspective? Yes?
18:39
Speaker 1: In art, Yes, right, I do like force perspective stuff
18:44
Speaker 1: I do. It's kind of cool, it's neat stuff. I
18:46
Speaker 1: guess that's that's probably part of the op art movement, right, Uh, yeah,
18:50
Speaker 1: when it was at like sixties and seventies. Yeah, it
18:52
Speaker 1: seems like yeah. And then you know, kind of coincided
18:55
Speaker 1: with drugs, right, not surprisingly. And then there's another one
18:59
Speaker 1: that I hadn't heard of, called atmospheric perspective. Had you
19:03
Speaker 1: heard of that one? I had not. So. Atmospheric perspective is, um,
19:07
Speaker 1: it's basically the dust, particles in the water, vapor in
19:10
Speaker 1: the air. The further something is a way, the more
19:13
Speaker 1: of an effect those things have on the detail you see.
19:15
Speaker 1: If it so your brain says, well, that's a little blurry. Uh,
19:19
Speaker 1: that's that's a far away object. And then there's there's
19:22
Speaker 1: plenty of other ones, but the gold standard is um
19:27
Speaker 1: is object size. Right, that's where you um, you know
19:32
Speaker 1: that roughly the size of an object, and you can
19:34
Speaker 1: use it to compare to see whether it's it's far
19:37
Speaker 1: away or close, depending on whether it's small or large,
19:40
Speaker 1: or if you don't know the size of an object,
19:42
Speaker 1: but you know two objects are identical and one is
19:45
Speaker 1: smaller than the other, well, then you know the smaller
19:47
Speaker 1: one is further away. So the brain is like constantly
19:49
Speaker 1: using all of these little cues and tricks to put
19:53
Speaker 1: together a conception of what it's seeing at any given
19:56
Speaker 1: point in time. And then what what um optical allusions
20:00
Speaker 1: are are Again these things you can produce to to
20:04
Speaker 1: reliably trick the brain into making these wrong decisions. That
20:07
Speaker 1: that shows its hand. It reveals how the brain functions
20:12
Speaker 1: to take these shortcuts and the tricks that uses. Right,
20:14
Speaker 1: Like a brain you think you're so smart, you're really dumb.
20:18
Speaker 1: Look at this, and the brain says, oh, stop looking,
20:22
Speaker 1: stop looking at those things, look at normal things. Um
20:27
Speaker 1: kind of like sorry, I kind of like the apparent
20:30
Speaker 1: motion ones, although I can't look at a lot of them. Um,
20:34
Speaker 1: those are the ones where something is drawn in such
20:38
Speaker 1: a way that it looks like it's moving when it's
20:40
Speaker 1: not right. The very famous snake illusion is a great example.
20:44
Speaker 1: And you know, this is another one of those theories
20:47
Speaker 1: that to me is a little weak. But one of
20:49
Speaker 1: the theories is that, um, they're these almost like unnoticeable
20:54
Speaker 1: rapid eye movements that we make. Uh how do you
20:57
Speaker 1: pronounce that? Yeah, no, s A C C A D
21:02
Speaker 1: E s YEA CICADs the cads. I think you could
21:05
Speaker 1: probably get away with either one. All right, Well that's
21:07
Speaker 1: what they're called. And uh, it's it's like Pruett Taylor
21:10
Speaker 1: Vince syndrome. You remember him. Yeah, he's a great actor,
21:15
Speaker 1: Yeah he is. Um, so those little movements he usually
21:19
Speaker 1: get smoothed out by the brain, so we you know,
21:21
Speaker 1: get like a static picture. But um, what it's causing
21:25
Speaker 1: in this case is perceiving motion where there was no motion.
21:28
Speaker 1: And then the other theory on this one for apparent
21:30
Speaker 1: motion illusions is there's just so much information going on
21:35
Speaker 1: that uh, you know, there's just confusion. Right. I saw
21:40
Speaker 1: one that actually combined the two that that's basically said, Um,
21:44
Speaker 1: the the CICADs are creating the illusion of motion, but
21:49
Speaker 1: what they're really doing is because the brain is being
21:52
Speaker 1: hit with all this visual information that is just totally
21:55
Speaker 1: doesn't make sense that we never never happen in nature
21:59
Speaker 1: except maybe in motion. That these CICADs actually each time
22:03
Speaker 1: your eye makes this tiny movement, it refreshes this overwhelming
22:08
Speaker 1: um overload of information onto the brain, which creates the
22:13
Speaker 1: sensation of movement. Oh yeah, pretty cool. Well, one of
22:18
Speaker 1: the cool aspects of all of this to me is
22:21
Speaker 1: um is the fact that once you've once you've seen
22:25
Speaker 1: the illusion and the trick to it, you can't undo that, right,
22:30
Speaker 1: So the brain is like a, ha, you know, I
22:32
Speaker 1: got this one, like you know, the famous one, the
22:35
Speaker 1: old lady or the or the young woman, the black
22:39
Speaker 1: and white. It's a you know, classic illusion. And once
22:42
Speaker 1: you you know, you can stare at and be like,
22:44
Speaker 1: I just see the young lady or I just see
22:46
Speaker 1: the old lady. Once you've seen both, then your brain
22:50
Speaker 1: has like I said, it says ah, and it files
22:52
Speaker 1: that away as prior knowledge and a little folder in
22:55
Speaker 1: the brain and you can't undo that. So once you've
22:58
Speaker 1: seen it, and you've seen the trick. You can aways
23:00
Speaker 1: look at it and kind of make that flip in
23:02
Speaker 1: your mind, right exactly. And it's the same thing too
23:05
Speaker 1: with them contour less figures. Where is it a wine
23:09
Speaker 1: goblet or is it two people's faces facing one another?
23:12
Speaker 1: Kind of thing? Right? Oh yeah, yeah, yeah, you know
23:15
Speaker 1: the negative space. Yeah, And apparently the trick to those
23:18
Speaker 1: is you focus on the black or the white and
23:22
Speaker 1: you see whichever one appears to be in the foreground,
23:25
Speaker 1: because what your brain is doing is saying, um, I
23:28
Speaker 1: need a foreground and I need a background, and then
23:30
Speaker 1: I've got something to work with, and depending on what
23:33
Speaker 1: it's which one it's looking at, it decides this is
23:36
Speaker 1: the foreground or this is the background. So it's either
23:38
Speaker 1: a wine goblet in the foreground or it's two people's
23:41
Speaker 1: faces in the foreground. You know, I wonder if this
23:43
Speaker 1: stuff if they know anything about because they didn't see
23:46
Speaker 1: anything in the research, but if they know anything that
23:49
Speaker 1: that this is like a brain exercise and helps you out,
23:55
Speaker 1: like you know, playing suduco or doing word puzzles, or
23:58
Speaker 1: if the brain is like stop looking at these, you know,
24:03
Speaker 1: I don't like this I can't take anymore, you know,
24:06
Speaker 1: or you know, like literally maybe, or if it causes
24:08
Speaker 1: stress on the brain by by taxing it in a
24:12
Speaker 1: way that it is not accustomed to or doesn't say
24:15
Speaker 1: it doesn't like. Obviously the brain doesn't have a you know,
24:17
Speaker 1: it's not a little person, but you know what I'm saying. Yeah, no,
24:21
Speaker 1: I know what you mean. But the brain, even if
24:24
Speaker 1: it's not a little person, it could still not like things. Right,
24:28
Speaker 1: So let's take another break and then, um, I want
24:31
Speaker 1: to tell everybody what my favorite optical illusion of all
24:34
Speaker 1: time is. Alright, chuck, Yeah, I'm ready. Well there's two
24:59
Speaker 1: one I like slightly less than the other. Okay, so
25:03
Speaker 1: start with the second place one. Okay, I knew you
25:06
Speaker 1: were gonna say that. I think that's a great way
25:08
Speaker 1: to do it too. So you've got um, I don't
25:11
Speaker 1: know the name of it. I'm sure there is a name,
25:13
Speaker 1: but actually I think it's the contour less figure as well.
25:17
Speaker 1: You take three circles, and you cut a pie slice
25:21
Speaker 1: out of all of them, like a pac man, and
25:24
Speaker 1: you orient those pie slices so that each one forms
25:27
Speaker 1: what appears to be the corner of a coherent square,
25:31
Speaker 1: and you look at it, and you're like, well, there's
25:33
Speaker 1: a square right there with some that's overlaying four circles.
25:37
Speaker 1: But if you stop and think about it, there's no
25:39
Speaker 1: line whatsoever that that makes that square. It's your brain
25:44
Speaker 1: exclusively filling in some suggestible information to say, well, there's
25:50
Speaker 1: a square over a field of four circles. It's pretty
25:53
Speaker 1: neat to me. I like that one. Uh so what's
25:56
Speaker 1: what's number one? Um? Yeah, it's called the Addleston checkerboard. Okay,
26:04
Speaker 1: surely you've seen this one, right, So I'm looking it
26:06
Speaker 1: up as we speak. It's from the nineties. There was
26:08
Speaker 1: an M I. T Vision researcher named Edward Addolson and um,
26:13
Speaker 1: he created this checkerboard where on the checkerboard there's you know,
26:17
Speaker 1: dark and light squares like a normal checkerboard, and then
26:20
Speaker 1: there's like I think, a cylinder on the checkerboard and
26:23
Speaker 1: it's casting a shadow. And so um, he says, look
26:28
Speaker 1: at this white square and then look at this black square, um,
26:32
Speaker 1: which is lighter, which is darker. And you say, well,
26:35
Speaker 1: that's easy. The darker square, figure B say, is obviously
26:39
Speaker 1: darker than figure A. And he says that's wrong, that's
26:43
Speaker 1: absolutely wrong. Figuring and figure B are exactly the same
26:46
Speaker 1: color and shade. Um, I'm looking at it. I've seen
26:49
Speaker 1: that one for sure. The whole thing. Um, it really
26:53
Speaker 1: really works because it takes it takes advantage of two
26:56
Speaker 1: different um tricks that you can play on the brain,
27:00
Speaker 1: or it takes advantage of two different shortcuts the brain makes. Right.
27:03
Speaker 1: One is that cylinder is casting a shadow, that's putting
27:07
Speaker 1: appears to be putting Figure A into um well into
27:12
Speaker 1: a shadow. Right, So your brain automatically makes assumptions that
27:16
Speaker 1: if something is in a shadow, it would normally be lighter,
27:21
Speaker 1: which is in this case an incorrect assumption. It's actually
27:24
Speaker 1: the same shade as the other one. And then the
27:27
Speaker 1: other assumption that's making is that because that square is
27:31
Speaker 1: surrounded by um squares of a darker color, uh, and
27:36
Speaker 1: it seems and it's in a shadow, it seems to
27:38
Speaker 1: contrast it where the other figure figure B is a
27:42
Speaker 1: dark square surrounded by light. Uh, it seems to be
27:45
Speaker 1: darker because of the it's surrounded, because the context of
27:49
Speaker 1: the squares that it's surrounded by. So your brain is
27:52
Speaker 1: using two different things, the presence of a shadow and
27:55
Speaker 1: then the context where if something is surrounded by lighter stuff,
27:59
Speaker 1: it seems darker. If something surrounded by darker stuff, it
28:02
Speaker 1: seems lighter. UM. And that's just not always the case, obviously,
28:06
Speaker 1: because Edward Adolson proved it's not. So you want to
28:09
Speaker 1: know My favorite the classic Ebbing House illusion E B
28:16
Speaker 1: B I N G H A U s uh. This
28:19
Speaker 1: one is sort of similar, but it's not so much
28:22
Speaker 1: about color, but it uses adjacent objects and a lot
28:25
Speaker 1: of these do too. They use other things surrounding something
28:29
Speaker 1: to trick your brain. Uh. And in this case, it's
28:32
Speaker 1: it's the classic one. Go look it up. It's the UM.
28:36
Speaker 1: You have two orange dots. One on the left, let's say, uh,
28:40
Speaker 1: is surrounded by six larger gray dots, and the other
28:44
Speaker 1: one on the right is surrounded by eight smaller dots.
28:47
Speaker 1: It's very simple, that's why I love it. And the
28:50
Speaker 1: orange dots are the same size, but they look completely
28:53
Speaker 1: different sizes, and it's just it's so simple. And I
28:59
Speaker 1: think this is one of the one is that UM
29:01
Speaker 1: and too they have this contest every year, I think
29:04
Speaker 1: for like, I don't know, it's been going on for
29:06
Speaker 1: at least ten or twelve years, right, uh for new
29:10
Speaker 1: illusions and like we said earlier. You know, a lot
29:12
Speaker 1: of these new illusions are still just sort of riffs
29:15
Speaker 1: on the classics. Um. But the one that won a
29:18
Speaker 1: couple of years ago was a new version of the
29:22
Speaker 1: ebbing House illusion where um, it's actually a video that
29:25
Speaker 1: you have to play, so it moves. Um that the
29:29
Speaker 1: outer dots they it looks like at pulsates and uh,
29:33
Speaker 1: well it is pulsating. They get bigger and smaller, and
29:37
Speaker 1: the orange dots stays the same, but it looks like
29:39
Speaker 1: it's shrinking and expanding, right, So it's kind of cool.
29:43
Speaker 1: It's just to just to play on the ebbing House illusion.
29:46
Speaker 1: But that's that's what we were saying earlier too. It's
29:48
Speaker 1: like it's almost like they invented all of them in
29:50
Speaker 1: the nineteenth century and then now we're just able to
29:53
Speaker 1: perfect him a little more. Yeah, pretty cool. Another thing
29:57
Speaker 1: I thought was really neat was that there's this biological
30:01
Speaker 1: basis that is the same for everyone on planet Earth, obviously,
30:05
Speaker 1: but they did find there some across different cultures that
30:11
Speaker 1: they didn't take the same visual cues necessarily. And the
30:14
Speaker 1: classic Mula Layah illusion that everyone has seen, and that's
30:20
Speaker 1: just the really simple one of two straight lines, horizontal lines, uh,
30:25
Speaker 1: and they have arrows on the ends. On one of them,
30:28
Speaker 1: the arrows are pointing out. On the other the arrows
30:31
Speaker 1: are pointing in. And those two horizontal lines appear to
30:34
Speaker 1: be different links. And so they did a study in
30:36
Speaker 1: South Africa and they found that most of the European
30:39
Speaker 1: South Africans thought, yeah, like, look at them, they're different links.
30:43
Speaker 1: Then they showed it to like, you know, the bushmen
30:45
Speaker 1: of South Africa, and they're like, no, dummies, they're the
30:50
Speaker 1: same weak can't you see that? And the researchers are
30:53
Speaker 1: like what yeah, and they really, I mean, they had
30:57
Speaker 1: some theories about it. Uh. That kind of makes and
31:00
Speaker 1: so that Western societies may be a little more used
31:03
Speaker 1: to these things that are built in straight lines and
31:05
Speaker 1: a little more geometrical, where the other culture might be
31:09
Speaker 1: like just more attuned to nature where there aren't so
31:12
Speaker 1: many straight lines. Right. And because the explanation for the
31:16
Speaker 1: what was it, the Meyer the mula, the Mueller liar effect,
31:20
Speaker 1: or optical illusion is that depending on which way the
31:25
Speaker 1: arrow was pointing, whether at the at the end of
31:27
Speaker 1: the line or away from the line um, the brain
31:31
Speaker 1: is used to seeing corners right. Two walls coming together
31:34
Speaker 1: at a ceiling make that that same kind of arrow,
31:38
Speaker 1: and one that's pointing away means the point of it
31:41
Speaker 1: is further away, so it would make the line look longer,
31:43
Speaker 1: whereas one that's pointing inward would make it look like
31:46
Speaker 1: the corners closest to us, right, so it would seem
31:49
Speaker 1: like the line is shorter. But but the explanation was that, well, bushman,
31:54
Speaker 1: have never seen two walls come together at the ceiling,
31:56
Speaker 1: so that's why it didn't happen to them. But the
31:58
Speaker 1: thing that just proved that is that, um, they trained
32:03
Speaker 1: UH computer to to look at this stuff, and they
32:06
Speaker 1: didn't train it on three dimensional objects, so it wasn't
32:09
Speaker 1: familiar with walls coming together with the ceiling, and it
32:12
Speaker 1: was fooled by it as well. So they were like, well,
32:14
Speaker 1: we we have no idea. What's going on? Then, bushman
32:17
Speaker 1: or magic is what they said. I wonder why so
32:20
Speaker 1: many of these UH illusion UH enthusiasts seemed to be
32:27
Speaker 1: like German and Austrian. I think I had to do.
32:31
Speaker 1: That was where the UH largely where psychology took off. Yeah,
32:37
Speaker 1: I guess that makes sense. I guess Escher was Dutch
32:40
Speaker 1: buzzy but um, yeah, it seems like a lot of
32:43
Speaker 1: these are like German and Austrian. Yeah. I think it
32:47
Speaker 1: has to do with that was where the hot seat
32:50
Speaker 1: of psychology and brain research was at the time. Interesting,
32:55
Speaker 1: h you got anything else? Actually I do have one more.
32:58
Speaker 1: There was um a guy named Hermann von helm Holtz.
33:02
Speaker 1: Oh he wasn't German, right, No, nice Irish guy who's
33:06
Speaker 1: from Indiana. Von Helmholtz came up with these um squares
33:12
Speaker 1: right that are not Actually they don't have confining lines
33:16
Speaker 1: or defining lines. They're just equal lines of squares or
33:20
Speaker 1: lines lines equally apart that formed to the brain a square.
33:24
Speaker 1: But ones that are horizontal seems smaller and shorter than
33:30
Speaker 1: ones that are vertical, which is weird because if you
33:35
Speaker 1: are wearing like a horizontally striped shirt, everybody's like, you
33:38
Speaker 1: look fat in that shirt. Well, von Helmholtz, you don't.
33:42
Speaker 1: You should actually look slimmer, which surprised me. So I
33:46
Speaker 1: started wearing horizontal stripes as a result. You got your
33:49
Speaker 1: Charlie brown shirt out. Yeah, because that was sort of
33:52
Speaker 1: the old I don't know if it's true or not,
33:54
Speaker 1: but they said that the New York Yankees designed their
33:57
Speaker 1: pin stripes to make Babe Ruth look thinner. I could
34:00
Speaker 1: totally buy that, but I don't know if that's true.
34:01
Speaker 1: I thought they had been stripes before then. But Babe
34:04
Speaker 1: Ruth was eating a steak while they were fitting him
34:06
Speaker 1: for and he said, thanks for thinking of me. But
34:08
Speaker 1: he wasn't even using silver. Is he eating it with
34:10
Speaker 1: his hand? Yeah? And he also, um uh, blended a
34:14
Speaker 1: steak into a milkshake and drank that along with his
34:17
Speaker 1: regular steak, right, And he didn't take a cigar out
34:20
Speaker 1: while he drank it. He just put that in the
34:22
Speaker 1: corner of his mouth. Yeah, And it's after dinner cognac.
34:25
Speaker 1: That's why we love Babe Ruth. Ye, you know what,
34:28
Speaker 1: we didn't get into it all. And I don't know
34:30
Speaker 1: if they even count as illusions or if there's something
34:32
Speaker 1: else or those and they were a boy, they were
34:34
Speaker 1: all the rage and the early nineties I feel like
34:37
Speaker 1: were those um magic I yeah, where you stare at
34:41
Speaker 1: the thing and all of a sudden a ship pops
34:43
Speaker 1: out at you. If you're you know, lucky enough to
34:47
Speaker 1: be able to see it. I know a lot of
34:48
Speaker 1: people that would just endlessly not be able to see him,
34:50
Speaker 1: and it would frustrate them to no end. I think,
34:52
Speaker 1: if I remember correctly, they advised that you stare into
34:56
Speaker 1: the middle ground. Yeah, and sort of like unFocus your eyes. Yeah,
35:00
Speaker 1: I was looking those up. Um. There's a Mental Floss
35:03
Speaker 1: article on it that was pretty brief and it made sense.
35:06
Speaker 1: I think they were machine vision learning researchers who were like, hey,
35:10
Speaker 1: let's make some money on the side if they start
35:12
Speaker 1: with like a depth map of something and put it
35:15
Speaker 1: in gray scale. And I think they make two of them,
35:18
Speaker 1: so your eyes are getting the two different versions of it,
35:22
Speaker 1: but one smaller than the other, so it really makes
35:25
Speaker 1: it pop as far as depth goes. And then somehow
35:28
Speaker 1: the random repeating pattern that overlays it transmits that information
35:34
Speaker 1: to your brain unconsciously. Well, so you did look it up,
35:38
Speaker 1: then I did. I don't know if I got it
35:41
Speaker 1: fully right because it's it's actually kind of complex, but
35:44
Speaker 1: I thought they did a pretty good I would describe me.
35:46
Speaker 1: Could you see those? Yeah? Sometimes sometimes Yeah, I always
35:50
Speaker 1: could see them. And that's another one of those where
35:52
Speaker 1: once you see it you can just immediately like draw
35:55
Speaker 1: it out. Um. And of course that's there's the one
35:59
Speaker 1: Ethan's supply and mall Rats sort of the one joke
36:04
Speaker 1: through that movie. It was he just stares at this
36:05
Speaker 1: thing like through the whole movie and he couldn't see it.
36:08
Speaker 1: I couldn't see it, poor guy. What a great joke,
36:11
Speaker 1: you know, speaking of that something that's always bothered me.
36:14
Speaker 1: Stephen King said, and one of his books or something
36:16
Speaker 1: like that, he was talking about how you can't unsee something.
36:19
Speaker 1: I thought you said, he's talking about Mall Rats. He was,
36:22
Speaker 1: and he he used the Man in the moon as
36:24
Speaker 1: an example. He's like, it's like the man in the moon.
36:26
Speaker 1: Once you see it, you can't unsee it, right can
36:30
Speaker 1: I Like, I've seen the man in the moon before
36:32
Speaker 1: and I totally can't find him again, so you can
36:37
Speaker 1: un see it. Stephen King is wrong? What is the
36:39
Speaker 1: man in the moon? What are you talking about? You've
36:41
Speaker 1: never seen the man in the moon now, so I
36:44
Speaker 1: guess probably look it up. I think it would help
36:47
Speaker 1: to see somebody else pointing it out. And then when
36:50
Speaker 1: you see the when you look at the full moon,
36:51
Speaker 1: you you should be able to see it. But there's
36:54
Speaker 1: a man looking down. It's Jackie Gleeson. I don't think
37:00
Speaker 1: are you looking it up right now? Yeah? I'd never
37:04
Speaker 1: do that was a thing that's weird. And then the
37:06
Speaker 1: Japanese think it's a rabbit and that the rabbit is
37:09
Speaker 1: up there making mochi. Really, I don't know what other
37:13
Speaker 1: cultures think. Those are the two I'm familiar with. Huh yeah,
37:18
Speaker 1: so mochi. All right, if you want to know more
37:22
Speaker 1: about optical illusions, type those words into the search bar
37:25
Speaker 1: at how stuff works better yet, go to Michael Bach
37:29
Speaker 1: dot d E and just have some fun. Uh. And
37:32
Speaker 1: since I said d E, it's time for a listener mail.
37:37
Speaker 1: I'm gonna call this Aussie slang. We love our and
37:41
Speaker 1: I said Aussie. I met Aussie, right, we love our
37:44
Speaker 1: Australian listeners. We've got a lot of them. They've long
37:48
Speaker 1: supported the show, so we'd like to shout them out. Yeah, Australia. Uh,
37:51
Speaker 1: he said, get eye, fellas. That's pretty good. I'm not
37:55
Speaker 1: gonna read the whole thing like that, but I will
37:57
Speaker 1: just nailed Canberra. I'm a debut a listener from down
38:00
Speaker 1: on and I'm doing my best to get through your podcast.
38:04
Speaker 1: I love the show and finish every show with a
38:05
Speaker 1: smile and some new fact to tell my mates about. Anyway,
38:08
Speaker 1: I got a quick story for you to have a
38:09
Speaker 1: laugh at and possibly be very confused by the Other night,
38:13
Speaker 1: my mate and I were going on a uh Marcus
38:15
Speaker 1: run M A C C A S. I think we've
38:18
Speaker 1: talked about that before, right, didn't that beer? I don't know?
38:22
Speaker 1: Uh Fosters was us Chilian? And he goes, OHI mate,
38:28
Speaker 1: after we've been to Macus, we can drop by the
38:30
Speaker 1: sub grab a packet dairies and then the bottle. I'll
38:33
Speaker 1: grab a slab of EV Studies and head back to
38:36
Speaker 1: yells and get piste. Okay, so let me let me
38:40
Speaker 1: oi mate, Hello friend, after we've been to Marcus after
38:45
Speaker 1: I don't know what that was. Next, can we dropped
38:48
Speaker 1: by the servo? We can go hang out with Tom Servo.
38:53
Speaker 1: I bet you anything. A servo is like a gas station.
38:56
Speaker 1: Grab a pack of dirries, Uh, get some milk and
39:01
Speaker 1: then the bottle. Oh uh, get a bottle, grab a
39:06
Speaker 1: slab of v B Studies, get some ribs. I think
39:11
Speaker 1: I think that's it, uh, and head back to yours
39:15
Speaker 1: and get pissed uh and then go to sleep. I
39:18
Speaker 1: think you're right on the money. Yeah, I know you
39:22
Speaker 1: guys don't often do request be rad If you guys
39:24
Speaker 1: did a podcast on Aussie slang's history and meanings, mostly
39:28
Speaker 1: because I would love to hear Chuck's Aussie accent. Oh
39:30
Speaker 1: well yeah, granted he didn't wait, he didn't translate it
39:34
Speaker 1: himself now, so we'll never know whether I was completely right.
39:37
Speaker 1: Someone someone will uh. And I'd love to hear both
39:40
Speaker 1: of you pronounced as much Assie slang as possible. But
39:43
Speaker 1: also because i'd like to have facts about why I
39:46
Speaker 1: speak the way I do. Stay rad And that is
39:49
Speaker 1: from Liam and he said, ps, we swear a lot
39:53
Speaker 1: down here. Uh. And if that's why you can't do
39:56
Speaker 1: an Aussie slang podcast, I don't blame you. Well, I
40:00
Speaker 1: swear a lot. I r L Liam, but we just
40:03
Speaker 1: keep it clean for the show. That's right. Nice? Yeah,
40:08
Speaker 1: well thanks Liam. I'm not gonna do an Australian accent
40:11
Speaker 1: because it would hurt everyone's ears. Uh. If you want
40:15
Speaker 1: to get in touch with us, like Liam did, you
40:16
Speaker 1: can tweet to us. I'm at josh um Clark and
40:19
Speaker 1: at s y s K podcast, Chuck's on Facebook dot
40:22
Speaker 1: com slash Stuff you Should Know, and Charles W. Chuck
40:25
Speaker 1: Bryant and you can send us an email to Stuff
40:28
Speaker 1: Podcasts at how stuff works dot com, and it's always
40:30
Speaker 1: hang out with us at her home on the web.
40:32
Speaker 1: Stuff you Should Know dot com For more on this
40:39
Speaker 1: and thousands of other topics. Does it How stuff works
40:41
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