some things are discovered accidentally the discovery of penicillin was an accident Alexander Fleming came back from his holidays and noticed that something had killed the mold on an old petri dish he called it penicillin the microwave oven was invented accidentally a scientist working on a magnetron in 1945 noticed that some strange Force had melted a chocolate bar in his pocket many optical illusions were discovered accidentally as well the famous cafe wall illusion was discovered by a scientist as he sat in his local cafe probably the most incredible optical illusion certainly the most incredible one that
I've ever seen was also discovered by accident an undergraduate was working with photographs of faces for an experiment that he was working on when he noticed that under certain circumstances the faces turned into hideous and grotesque forms the effect was developed and named by Jason tangent Shawn Murphy and Matthew Tompson of the University of Queensland and they entered it into a worldwide competition the best illusion of the year contest 2012 they came second pipped to the post by a mindbending disappearing handrick it's a great trick but in my opinion the flashed face Distortion effect should
have won they were robbed the flashed face Distortion effect currently defies explanation let's jump straight into this illusion and initially I'm going to use the same video that was created for their entry into the contest in 2012 I'm going to play it twice for you first firstly I just want you to look at the faces on the video I think you'll agree that they are all perfectly normal and good-look faces there's nothing unusual about these faces at [Music] all now I'm going to play that exact video again with one new rule and that's to focus
your stare on the cross in the center of the screen so that you're only viewing the images with your peripheral vision it's important to note that the video I'm about to play is exactly the same video that you've just seen no images have been altered focus on the cross and I'll play that video [Music] again o [Music] [Music] so what's going on there I saw at least one Cyclops you like me probably this time saw those faces as grossly distorted and grotesque almost cartoonish the special effects department on a Hollywood film couldn't have done a
better job so what's going on science as yet hasn't fully worked out what exactly is happening in our brain to cause this effect certainly it's telling us something about how our brain is processing images from our peripheral vision the alignment of the eyes and possibly the nose seems to have a material effect on the illusion the presentation rate also seems to have a material effect I've had a go of making my own version of this aligning the noses and the eyes and keeping the presentation rate similar first of all let's look at the video normally
again to satisfy ourselves that these are all perfectly normal and pleasant looking people [Music] now let's watch it by focusing on the cross in the middle of the screen [Music] I've tried my version with a lower presentation rate and in some instances the results seem to be even more hideous [Music] we don't experience the world as it is we experience the world as our brain perceives it thank you so much to the discoverers of the flashed face Distortion effect for allowing their video to be shared if you enjoyed it then you'll love what's coming up
next I put together a selection of optical illusions last year and I'm going to play the best ones for you right now there are more examples of how our brain sometimes just gets things wrong please allow me just 20 seconds to plug this channel very nearly interesting is a brand new channel and I need all the help I can get please click that like button if you've enjoyed this video that's how YouTube knows you like it and they'll show it to more people and please consider subscribing that way I might see you again and now
you can support the channel on patreon where you'll find exclusive content and a grateful me there's a link in the channel description let's begin with the Lilac Chaser this illusion is over 20 years old and was created by Jeremy Hinton it's a visual illusion that demonstrates color adaptation if you follow the dots around you'll notice that the discs are simply disappearing for a split second but if you focus on the plus sign in the center you'll see that the Gap has been replaced by an after image of the opposite color in this case green that
image isn't actually there our brain has made it up if you stare at the cross for over 20 seconds you may experience a phenomena called Troxler fading where all of the dots disappear seemingly mopped up by the Green Dot which doesn't even exist I'll leave it running for another 10 [Music] seconds the penro stairs made popular by Lionel and Roger Penrose going clockwise you're always going downhill in one continuous loop this structure is impossible to recreate in three dimensions but it well and truly fools our brain which cannot make any sense of it I'll give
you another 10 seconds to imagine yourself walking down these NeverEnding steps [Music] the Herring illusion was discovered by German physiologist ELD herring in 1861 are those red lines parallel or are they Bode I'll give you 5 Seconds to work it [Music] out they are of course perfectly parallel but we see them as bod When lines are presented in front of a radial background our brain can't fully understand what's going on [Music] the hollow face illusion perfectly demonstrates that we have an incredible inbuilt bias for seeing faces as convex over millions of years of human evolution
we've recognized faces as convex because they are of course convex but if a face is presented as concave something kicks in we immediately convert it to convex such as the strength of this deep-seated cognitive bias these computer-generated Hollow faces play Havoc with our brain I'll leave this running for another 10 seconds there's such fun to [Music] watch the justr illusion is named after Polish American psychologist Joseph jastro any parent watching that struggled to dispair beir with wooden train tracks knows exactly what I'm about to say which piece of track is the longest I'll give you
5 Seconds to work it [Music] out they are of course exactly the same size but that's not what our brain is telling us there is no universally accepted explanation here as to why our brain is getting this wrong the most common theory is that the brain gets confused because of the comparisons with an inner and outer radius I'll digitally overlay the pieces of track to prove that they are in fact the same size now everything makes sense until I put it back into its original place and it all goes wrong again the Checker Shadow illusion
was published in 1995 by Edward Edelson your brain is telling you that tiles A and B are different [Music] colors they are in fact exactly the same color and shade your brain can see the Shadow and clearly expect a White Tile to be in the space marked B I'm going to slide the B tile now Out of The Shadow and put it next to a I haven't changed the color of that tile your brain [Music] has the spinning dancer it's one of the most stunning visual Illusions whether the spinning dancer is spinning clockwise or anti
clockwise depends entirely on how your brain is interpreting the image this illusion derives from the lack of visual cues for depth the crazy thing about this illusion is that it can switch directions at any moment sometimes looking away and then back at the screen can trigger this switch but other than that you've got no control over it once you see the spinning dancer switch directions it's not the video that's done that it's your brain I'll keep it running for 20 more seconds if it hasn't worked for you rewind it and have another go [Music] Roger
Shepherd's tables these Tables by Roger Shephard are an example of geometrical illusion they are stunning and the very best example of its type what would you say as the longest table the tabletops are a pair of identical parallelograms and our brain interprets them as objects in three-dimensional space this one clearly looks longer and thinner than this one they are however identical I can show graphically by moving the large tabletop over and I can even use a ruler to show you that they are the same if you don't believe me pause this video and compare the
length of your finger to both examples the zna illusion was discovered by German astrophysicist Johan Z ER in 1860 are the long lines parallel I'll give you 10 seconds to work it [Music] out the long lines are perfectly parallel the repeated short lines are either horizontal or vertical these short lines give the impression that the long lines are not parallel your perception of even the short lines may also be distorted let me take a away the short lines now your brain can make sense of [Music] it these horizontal lines are perfectly level and straight but
that's not how your brain is interpreting it the crazy thing is though if we use exactly the same image with colors of lower contrast your brain can make sense of it it was named the cafe wall Illusion by Richard Gregory in 1973 a member of his laboratory team noticed the effect on the wall tiles at their local cafe here's Richard in 2010 visiting that exact Cafe the sander illusion named after German psychologist Friedrich sander who published it in 1926 which diagonal line is the longest this one or this one I'll give you 10 seconds to
work it out you may not believe me but the lines are in fact identical in length our brain is getting confused about these lines within the distorted parallelogram to prove this you can pause the video and measure it on screen but I'll also disassemble it for comparison you do need to trust me here I have not changed the length of these lines your brain has I leave it on screen for another 10 seconds to see if you can make any sense of [Music] it thank you so much for watching this video If you enjoyed it
please click the like button that way YouTube will show it to more people and please consider subscribing that way I might see you again and please have a look at some of the other content on the channel there's lots of interesting things on there well very nearly interesting
