Disturbing face distortion illusion

By Phil Plait | July 15, 2011 10:48 am

This is a pretty nifty illusion: as you look at a spot between two rapidly changing images of faces, your brain distorts the images, making them look really weird:

I could do without the title they chose for the video, but the paper on which it’s based is called "Flashed face distortion effect: Grotesque faces from relative spaces", which may not explain much, either. What it means, basically, is that as the faces flash, certain features get distorted by your brain, and the amount of distortion depends on how much that feature deviates from the rest in the set. In other words, someone with slightly larger eyes gets perceived by you as having huge eyes. Go ahead and pause the video and click through it; the faces are pretty much normal faces, so the distortion really is an illusion.

I think that’s pretty neat; I’m fascinated by how our brains perceive faces in particular, since people see them everywhere. I’d love to see some variations on this, like showing men’s faces, or a man on one side and a woman on the other. Would it work for animal faces too? Hmmm.

I’ll note that some people have a hard time seeing this illusion; my friend Richard Wiseman — who knows a thing or two on how the brain can be fooled! — doesn’t see it well. Do you?

Tip o’ the Nacker cube to Gizmodo and my old friend Bill Dalton.

CATEGORIZED UNDER: Cool stuff, illusion, Pareidolia

Comments (58)

Links to this Post

  1. 11. Eyecandy: Strange Faces « Tikkunista! | December 16, 2011
  1. Chip

    If I remember correctly I think there was an episode of the old Seinfeld sitcom that did a show about this exact thing.

  2. I saw this the other day, and I was wondering if the specific order, or even just the degree of variability if the faces from one to the next helped to emphasize the illusion. If you displayed the faces in a different order, or had made other choices for the left/right pairs, would the illusion go away? I wonder how it would work with a randomly ordered set of portrait pairs?

  3. Oh man, that’s awesome!
    The changing outline of the photos seems to have an effect. I wonder if the faces were masked to the same outer shape if the effect would be as pronounced…
    Some -DO- seem to be bug-eyed, too! Cool!

  4. HP

    I wonder if this is related to the distortions that occur that when you stare at your own reflection in extremely dim light?

  5. Joe Dickens

    There’s a problem with this… most of them ARE ugly. Some even look like they’re male and not female.

  6. Dr Dreadful

    Phil, you forgot to close your tag and now I have to lean to the right to be able to read the rest of the blog…

  7. Daniel J. Andrews

    Pretty cool. Hadn’t heard of this one before. One way I was able to substantially reduce the illusion was to set my eyes as if I was looking at one of those magic eye 3D posters or interpreting two overlapping aerial photos. Not terribly ground-breaking, but I do like knowing about illusions and how to see through them.

  8. ShavenYak

    HP: No, silly, that happens because your body is temporarily possessed by the soul of Queen Mary I of England.

  9. Gordon

    I’m not sure what I’m meant to have seen… faces?

  10. kevbo

    Holy crap. They look like cartoons to me when I look at the crosshair!

  11. Ethyachk

    Hmm… I get vague flashes, but mostly I just see a bunch of faces.

  12. George

    The effect even happens when you stare at just one face. Since the registration point seems to be the eyes, they stay steady perhaps implying continuity over the different faces. With that steady point of reference and everything around changing, it seems logical that one would interpret the successive faces as some kind of grotesque morphing. I reckon the effect wouldn’t be as pronounced if the registration point were the base of the neck or edge of the body such that the observer didn’t have a steady reference point within a facial feature.

  13. Brian

    I too got the effect even looking directly at a face. When looking at the crosshairs, I got lots of blocky outlines, almost like they were World of Warcraft avatars. I even thought I spotted a cyclops at one point!

    BTW, it’s spelled “Necker Cube” (unless “Nacker Cube” is some obtuse pun on “knackered”, in which case never mind).

  14. Sam H

    I didn’t watch the video, but Phil: why and how did 90% of BA suddenly decide to italicize itself?

  15. Elgarak

    The first time I watched it, I put my eyes close to the screen. Two images side-by-side, like stereoscopy, which I can do better watching close, right? The effect was there, but not very strong, and I was easily pushed out by focusing on just one face.

    Turns out that the effect works MUCH better when you move away, and really concentrate on the center cross. Helps if you watch on an iPad…

  16. Chief

    I was under the impression of the features of each face taking on the aspects from the other. The eyes on the left were superimposed on the face to the right, same with lips. I noticed that my focus was more on the right face as well, even though distortion was evident on the left and right one.

  17. ST

    It was actually kind of disturbing to watch.

  18. The effect works even if the faces DON’T flash.

    Stare at the crosshair, and pause the video. Frame advance to the next pair of faces. SO LONG AS you don’t take your eyes off the crosshairs, the two faces look like demonic ogres. The MOMENT you move your eyes to one of the faces, it pops into “normal” — then that face STAYS looking normal even if you move your eyes back to the crosshairs.

    In other words, it’s not the flash that’s distorting the face, it’s NOT LOOKING DIRECTLY INTO a face that you haven’t yet formed a mental picture of.

  19. Re #16: I don’t know. Even when I look directly at the flashing faces, they start looking kind of freaky to me.

  20. Paula Jones

    I saw this the other day, too. Freaky. I’m thinking maybe we are seeing ‘reality’ when we see those odd looking people. If we are all ‘agreeing’ on a consensus reality for our daily physical existence then we have ‘agreed’ to appear a certain way to one another. When you play with this little photo montage you are seeing what we REALLY look like.
    Ha! Now we know…ewwwww!

  21. I was able to see it. Before reading your explanation for the effect, my thought was that there was some lag in the brain with processing different parts of the face which resulted in overlap.

  22. Calli Arcale

    That is really really freaky. I see it very strongly as long as I fixate on the cross. If I look at the faces, they look fine, even while flashing, but when looking at the cross they look hideously deformed — alien, even.




  24. Jeffersonian

    Awesome effect. I saw pigs and all sorts of evil homunculi that would have enticed David Cronenberg.

  25. Peptron

    Not sure if that effect has a name, but you can reproduce it easily in front of a mirror.

    Stand in front of the mirror, looking at yourself directly, and make funny faces. Opening your mouth big, your eyes big, shrinking them, etc.

    Now: Do the exact same thing, but looking at some point next to your reflection in the mirror, so that your reflection is in your peripheral vision. As you switch expressions, your face will become monstrously distorded. Your eyes will become monstrously huge, your mouth will almost cover your entire face, etc.

  26. james

    I think what is happening is, your brain is trying to recognise facial features… But can only normally do this with one face at a time… It can’t cope and turns each face into a mix of the two.

    It works for me, even with the video paused.

    This gives strong evidence towards the theory that our visual system works by making decisions. This type of image causes it to make a mistake about what it is seeing.

    So seeing, is not always believing.


    Why does the title bother you?

  28. tmac57

    Someone should sent this to David Icke.

  29. Anchor

    I can see it even when looking DIRECTLY AT the faces. But I notice the ‘carryover’ effect from the previous face is also more pronounced when fixating near or between the eyes. When fixing on the nose or nostrils or the mouth, the effect is much dampened and all look pretty ordinary. The eyes seem to carry the least amount of dreadfulness. Most of the grotesquery seen in the peripheral field seems to take place in or near the mouth – just where one would expect any evolved instinctual expectation of danger might lurk. (Presumably the response is associated with the primitive parts of the brain like the limbic system or reptilian cortex). After all, our ancestors had to avoid being eaten, and the mouths of predators are threatening and have the power to terrify at the mere sight of them.

    It would be interesting to see flash-faces carrying wide open-mouthed toothy smiles or ‘happy-faced’ laughter on one side to see if the effect is even more magnified over the neutral expressions like those here. It might produce quite a striking parade of grimacing monsters, demons and gargoyles.

  30. Seth

    I see it very strongly. Everyone looks like a crazy alien to me. However, I noticed that if I pause the video and continue to stare at the cross, the faces still look extremely distorted, even though they do not change. So there must be something more to this than just the changes between the different faces.

  31. Peptron

    @27. Seth

    To me, it seems to be almost exclusively caused by the fact that the peripheral vision doesn’t see details and has to “guess” what’s there based on what was there before. Break the continuity, and you shortcut the brain.

    All you have to do is to look at the 1st two faces, stare at the center until you start to get an after effect, and then click somewhere else in the video. Voilà, without any flashing you get the distorded effect.

  32. Cynthia Moreno

    Wow thats friggin weird.

  33. Required

    I also would like to know what is wrong with the title? If it’s the first thing worth mentioning, shouldn’t it at least be worth explaining?

    Here’s an explanation of why the title is fine:

    It seems to me the illusion is being demonstrated using photos of attractive women in order to show a difference between the real faces and the distortions of the illusion. I imagine someone who notices a grotesque distortion on an unattractive person might not be able to convince themselves after the fact that the person isn’t actually that weird looking.

    What’s your reasoning for not finding the title appropriate?

  34. tmac57

    My guess is that the effect is caused by the persistence of vision coupled with the extreme differences between subsequent images.Features that are compatible within one face when carried over to the next are incongruous,and unexpectedly odd.Your brain is trying to reconcile the images into some coherent flow,but keeps getting thrown a curve between what it expects to see and something vastly different.Either that or they are reptilian aliens.Those are the only two possible choices.

  35. Grand Lunar

    Very weird indeed!

  36. QuietDesperation

    It’s quantum. We really are demonic ogres, but our minds correct it to something bearable when we make a direct observation of the faces.

    Most of the time the eyes just bug out, but occasionally I swear I see snake eyes.

    Be afraid.

    “I’m fascinated by how our brains perceive faces in particular, since people see them everywhere. “

    We’re wired for it.


  37. CR

    Not to put words into Phil’s mouth, so to speak, but I think he dislikes the title because ‘pretty’ and ‘ugly’ are very subjective terms. Might not someone feel that the opposite is occuring (ugly to pretty, in other words)?

  38. Didn’t really work for me. I saw lots of different faces flickering and running through in the sequence but none seemed particular grotesque or misshapen.

    Just looked like some photos had been taken from closer up and some from further away. Was that the illusion? Certainly NOT the best one I’ve seen or that you’ve posted here, but then maybe it’s just not working for me.

  39. Robert

    I wonder if this could detect face blindness? Face blindness causes some individuals to be unable to distinguish faces. Most of them go through their entire lives without ever being diagnosed – they distinguish individuals using broader height, hair colour, size etc characteristics.
    The fact that this doesn’t show to some makes me think that it might be somehow related.

  40. Andre

    I think this illusion is occurring because of a number of things:

    1) Individual backdrops have been removed and replaced by a white background. Therefore, the head and hairdo size distortions are being played-up for dramatic effect.

    2) The color tones of the pictures are not constant. Half of the frames have been color shifted towards the green end. Pretty ghoulish.

    3) The portraits themselves are off-putting. No one is smiling. Some have cold-sores and others fresh pimples.

    4) The images are washed out. They are not sharp. It’s as if they were taken at a low resolution and enlarged 300%. Normal human faces are not creamy pale.

    In conclusion, this “trick” is heavily biased.

  41. Rift

    #5- sigh

    And people thought Phil was wrong for his “don’t be a dick” speech a year ago, because he didn’t give specific examples.

    Exhibit A.

  42. panini

    I’ve seen this video around the intertubes and most men are commenting “they are actually ugly”. Can we talk elevatorgate again?

  43. Lisa

    I feel like this has nothing to do with the flashing. I kind of see it if I follow the directions and stare at the cross, but I feel like I’m not even really seeing the faces. If I actually allow myself to look at the faces, then I occasionally think, WOW that person was really weird looking, but if I go back and look at the still frame it turns out they were just a weird looking person.

  44. Robert @ 38, I have always believed that I have a touch of face blindness (or prosopagnosia) and I do get the monsterism effect when I stare at the center, but not if I focus on one face. I’m guessing that this is just an issue with our face-processing software – “do these lips on the right go with that chin on the left and those cheeks that just appeared?” We wind up creating patchwork faces out of pieces of four or more different faces at once.

    Testing, testing: does this fix the italicization issue?
    Drat, apparently not.

  45. Neeneko

    This is a fascinating demonstration at how human’s image processing tends to malfunction when exposed to things it didn’t evolve for.

    The reason you get such a strange effect is the vast majority of what you ‘see’ is essentially generated. Human vision is remarkably low resolution, only about 100k pixels. We generate a fuller image by constantly moving our eyes around to cache data, then the brain fills in the blanks based off what it expects to see. If you take the movement away and then give the brain ‘impossible’ input, its ability to generate the rest of your vision can get very glitchy.

  46. Alexrkr7

    I think the title is inaccurate and a childish way of describing what’s happening. First of all they’re not all women. Secondly, “pretty” is subjective. Thirdly, it’s not pretty to ugly; it’s normal human faces to (at least to my eyes) distorted versions of human faces. Much like those effects you get on mac webcams. Lastly, this is a really cool demonstration of the inaccuracy of our perception and the title doesn’t get that point across. If the video weren’t here or described by Phil I would assume it were some 14 year olds dumb photoshop jobs and not a cool piece of science.

    Take a look at the comment section of the video on youtube. Most people seemed to be confused about what’s supposed to be happening because of the title.

  47. Ok2panic

    I just see faces. No distortions.

  48. Becki

    One thing I noticed when I slowed down the faces: the eyes of every woman seem to be in the same place. Other head parts, however, were different distances from the eyes. Maybe it was just the small segment I went through. But when I watched it through the first time, the eye size seemed to be related to how much “movement” there was in the rest of the head. More distance between, say, the eyes and the hairline or the ears, the more the eyes looked distorted to me. Just a thought.

  49. Grimoire

    Why does the title bother you?

    Because it’s 2011, and we have to be politically correct to a level of obsessive compulsiveness that would otherwise be considered a candidate for medical intervention.

    Pretty and ugly are now banned words as their usage in this case might bring offense to the Ogre and Orc-American communities. Beauty is now a taboo concept unless it relates to something completely lifeless and random like a star cluster.

    Are there any other words we should fear? Might as well get them all out of the way, and reduce language to vague neutrality.

    Meanwhile, the rest of us who can still think clearly will continue to use the tools of language to their fullest extent, and sometimes wish we are not the same species as the terminal hand wringers.

  50. Grimoire

    I’ve seen this video around the intertubes and most men are commenting “they are actually ugly”. Can we talk elevatorgate again?

    Or those are people who are seeing the distortion effect to a high degree, creating spooky, hideous faces that an an actual sane person who does not fear using applicable words might suggest are ugly.

    But, no, because it’s men it has to be something terrible. BING! Surprise! You’re the bigot here! Oops!

  51. JediBear

    The only real effect it has is making my eyes water. I don’t know if that’s because I can’t simultaneously focus on the cross and recognize the faces as such or what…

    Which is another question, we’re looking at images out of focus. Is this an optical illusion, or an optical effect? Or some of each?

  52. Teshi

    I am so pleased people here are discussing the illusion and not, “Lol, all these women are ugly anyway” which is what seems to be the general feeling elsewhere.

    I hate to break it to the heterosexual male internet, but this is what most people look like. Take the makeup off your girlfriend, tie her hair out of her face, sit them face onto you in bright, white light, have them not smile, photograph her and she will very likely look like this. Normal. Also, all of them are women. Someone suggested they were not– they all are women. Some women just have a square jaw.

    People always look much better in real life motion, I find. Static faces are always not as we expect them to be.

    I see this illusion just fine. It also works for me if I cover one of the faces and look at the cross, so it’s not that there are two faces visible that is the problem. I think it’s that we do not get the right proportions until we look straight at something.

    I wonder if it would work with animal faces? Perhaps monkeys or something further from humans like sheep or cows.

    I tried it again and …weird, now I don’t see it. Perhaps after a while my brain has got used to seeing either those particular faces are has adapted to seeing them normally out of the corner of my eye.

  53. I can’t see it, I just see women.

  54. QuietDesperation

    I am so pleased people here are discussing the illusion and not, “Lol, all these women are ugly anyway” which is what seems to be the general feeling elsewhere.

    Good start…

    I hate to break it to the heterosexual male internet, but this is what most people look like.

    …and right off the bigotry cliff. And this is what sparks the controversies. Instead of addressing specific people who actually made comments you don’t like, you lump together an entire group.

    I see the effect to a very strong degree. To me the distorted faces look like something from an X-Files episode, or drawings of the moth men.

  55. Carey

    Thanks for that, QD.

    @Teshi #52: I hate to break it to you, but heterosexual male internet users are not a single hive mind. This only appears to be a case of badly chosen words, so I encourage you to choose more carefully next time.

  56. QuietDesperation

    …the whole aim of Newspeak is to narrow the range of thought. In the end we shall make thoughtcrime literally impossible, because there will be no words in which to express it.” – Syme, from Orwell’s 1984

  57. JS

    I think if you look at the cross like you are suppose to, the illusion is there. I believe it is due to the eyes and eye brows and possibly the mouths making these women look like aliens.


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