The Sydney Opera House Illusion
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The Sydney Opera House Illusion

Hello. I… wood (would) be Lion (lying) if I said that today’s show was not going to be ella-phantastic because today we’re going to Banan – na ascorbic ac-id Pap-per towels tape Yard-stick 20 prepared slides for a microsc-hopefully have fun That’s right. It’s time for Michael’s toys a walk down memory lane for all of you hockey fans out there. Today we’re gonna talk about an illusion that I witnessed when I was in Australia I was in Sydney for Braincandy Live and I stayed in a hotel that had a magnificent view of the Sydney Opera House Take a look. It’s a beautiful view right? Watch what happens though, as I walk away from the window. The Opera House appears to grow larger or closer filling up more and more of the window until it dominates the entire view Okay so, obviously as I walk back and forth across my hotel room, the Opera House isn’t physically changing size. It’s just appearing to. This effect reminds me of a couple classic illusions, the first is the Ebbinghaus illusion We’ve all seen this one before we’ve got two orange circles. Now the question is which one of these circles looks larger? Since you’ve probably seen it before I’m sure you answered They’re both the same size, and you would be right; both of these orange circles are exactly the same size But people tend to say that this circle looks larger than this circle. That is, the circle surrounded by smaller circles looks bigger. So why? Is it because the circles that surround it are smaller? Does our brain get tricked into thinking that things are bigger if they’re surrounded by smaller stuff? Probably. But is that necessarily what’s going on in my hotel room? You see something else is going on in the Ebbinghaus illusion Not only is this circle, the one that tends to look larger Surrounded by smaller circles, the circles that surround it are also closer to it Because this circle is surrounded by larger circles those larger circles necessarily have to form a ring That’s further away from this orange circle, so there’s a larger gap in between them So what’s causing this circle to tend to look larger? Is it just the smaller circles around it? Or is it also the fact that it’s more crowded, that it’s container is smaller Well one way to investigate this difference is with the Delboeuf illusion This is a simplified version of Ebbinghaus where instead of changing the size of what makes the container, we’re only changing the size of the container itself, instead of using big circles, we’re using rings Now, which of these circles, the black solid circles in the middle, appears larger to you if you said they both look the same size Well then you’re pretty smart and have probably had a lot of experience with illusions because yes, they are the exact same size But people tend to say that this circle Appears larger the effect is quite mild I find it more mild to me than the Ebbinghaus illisuion But the fact that people do tend to say that the circle Surrounded by a smaller ring looks larger, leads credence to the idea that the size of the container something is in Does affect how we perceive its size So let’s go back to the Opera House illusion when I’m right up against the window, the Opera House is pretty far away. When I am on the other side of my hotel room It’s still pretty far away So it’s angular size, the angle that it takes up in my field of view has not changed very much But the window which is much nearer to me at all times is changing its angular size Quite quickly when I’m up right against the window I can’t even see the edges of the window in my field of view But from the back wall of the hotel room I can see the whole window So what this means is that as I walk backwards the container that surrounds the Opera House, the window Shrinks at a faster rate than the Opera House does, so what I’m left with is pretty much a version of this figure from the Delboeuf illusion. That probably has something to do with how this illusion works more so than the size of What surrounds the Opera House, because the objects that surround the Opera House when I’m near the window are Smaller in angular diameter than the objects that surround it when I’m on the back wall of the hotel room The illusion was really fun and honestly I spent most of my time in that hotel room walking back and forth enjoying the illusion you can see it for yourself by looking at anything out of any window as you walk away from the window since it’s closer To you its angular diameter will shrink at a faster rate than what you see out the window and whatever It’s framing will appear to get larger We have a lot to learn about our visual systems from illusions like these because we still don’t have all of the answers But there are some very intriguing things about them For example What we do know about the Ebbinghaus illusion is that we are not Born to be fooled by it if you show this illusion to young children like under the age of 10 or under the age of Seven they tend to not be fooled they say well both orange circles are the same size. What do you mean? So, there must be something that we learn as we grow up that teaches us to be more Context-sensitive to perceive objects that are maybe surrounded by smaller stuff maybe in smaller containers to be Larger, but this is only a perception thing not an action thing other studies have found that if you would present this illusion to adults Who are fooled by it But then you ask them to reach out and grab One of the orange circles in the middle they will form the same grip size for each circle Now this is considered evidence for what’s called the two-streams approach to vision. The idea that our visual processing center has two different modes, one is perception how large we think things are how far away they seem, and the other Controls our muscles our actions. How we interact with those things and that part Isn’t fooled by the Ebbinghaus illusion, the Delboeuf illusion also Has all kinds of great little treats to give us one is that it may play a role in how much food we eat You see if you ask someone to put some food on a small plate like this And then you give them a larger plate and tell them to put the same amount of food on it They tend to put way more food on the bigger plate while thinking that they put the same amount on now Researchers have found that in the last say about a hundred years the average plate size has increased by about fifteen percent so That coupled with the Deloeuf illusion may be one of the things behind us possibly eating more nowadays I have done many many videos in the past about angular size so be sure to check those out It’s a fascinating topic and the illusions that it is Responsible for are just… well they’re just a blast we still have so much to learn from them. Please stay curious and Applier your curiosity to making the world a better place and as always mug Cilinder for watching


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