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By on May 9, 2011, with 105 Comments

Now here is a great find, Dylan pointed out to me. I’m not sure if you’ve heard of the McGurk Effect before (I haven’t), but in short, it’s a perceptual phenomenon which demonstrates an interaction between hearing and vision in speech perception. In practice, this audio-video optical illusion effect may be experienced when a video of one phoneme’s production is dubbed with a sound-recording of a different phoneme being spoken.

Perhaps, it might be best if I just let you watch this short, yet professional video BBC produced. It explains the whole deal, and includes some real-life examples of McGurk effect in action. Have we just “discovered” a whole new field of optical illusions to be showcased on this site? Could be… BTW, it might take some time before the video loads. It’s somewhat large, comparing to our previous video illusions!

  • genie

    Thats freaky!

    • Ed

      it is so funny.. when you cross your eyes making the 2 faces melt to a middle one when they are side by side, it works the other way around as well. I can’t get the middle picture to show the F movements of the mouth that way, while normally when overlapping 2 images I can switch to either one of them.

  • bluepool

    OMG cool! ^^

  • ohmygosh


  • some random guy you’l never meet

    that is freaky!

  • hysteria

    Wow! My ears are deceiving me!

  • Myname

    This doesn’t really work for me, I hear pah pah pah all the time.

  • Kaerlion


    That – is – a – ma – zing!

  • Sushi

    Thats is so cool!

  • Janelle McDermott

    This messes with my mind

  • Mars

    wowow…. thats really interesting actually! And I am not saying that sarcastically. I mean it is generally interesting!!!

  • Dew Silverdrop

    SSSSSOOOOOO CCOOOOOOOOOOOOL! very confusing! a great optical illusion! ps first comment!!!

    • mike

      yours wasnt the first comment
      it was mine or maybe someone elses
      mine didnt show up because it was waiting ”moderation”

  • roarshack

    holy crap! does this work for distance perception too? when they showed him at different distances the lady was talking so i couldnt tell..

    this is really interesting ‘cuz i’m studying psychology right now.

    they really did an excellent job of explaining sensation and perception.. something my class couldnt do for 2 weeks xD

  • Nixygirl

    Very very cool!!! More plz :)

  • Kimon Frousios

    That’s brilliant!

    The sounds for “P”, “V” and “F” form the group of consonants produced by the lips. There are other groups of related consonants as well.
    If you look at related languages/dialects, you’ll see that sounds from the same group are often interchangeable.

    I wonder if the illusion would work with a consonant outside the P/V/F group, like L.

  • Katie

    I’ve seen that entire documentary. It’s really amazing, you guys should all check it out if you’re into documentaries! :)

  • Andrea

    Awesome! Even when you know it’s the same sound, you still hear it differently!
    For me, as a speech-therapist, this is incredibly interesting, keep ‘m coming!

  • margaret marker

    I heard immediately that it was ba ba ba and then changed to fa fa fa . did not see this illusion..

    • Dylan

      You did see the illusion- because it DOSNT change to FA FA FA- the only sound he ever makes in every shot is BA. It simply looks like he is saying FA and that overrides what your mind hears.

    • Maggie

      Ohhhh I see now.. or I hear now.. closed my eyes and the sound stayed the same.. open them and the sound changes.. cool

  • Care Bear

    That was awesome! It’s another reason I don’t believe anything I hear and only half of what I see.

  • http://www.moillusions.com moe

    it doesnt work on me!!!!!!!!!!!!!!!!!!
    In the second clip, i hear ‘faa’!
    is that normal?

    • Dylan

      If you hear a FA then it worked lol- he isnt saying FA- ever- its all BA. his mouth movements look like FA but the only sound playing is BA- on every shot.

  • William Lim ‘nkm’

    cool !!!, its heard like he said “ba” first, but next picture I heard he said “fa”, altough its was a same sound

  • fossda

    ive seen this illusion before! its amazing!

  • Amazed

    WHOAH! That’s spooky O.o

    (btw, first?)

  • Steve

    Brilliant! This illusion has been one of my favorites since I first heard of the effect a couple years ago.

  • Someone

    I don’t get it. It sounds exactly the same. At first I thought the illusion was the opposite of what it really was. I had to force hearing the F sound.

  • Macy


  • josephine

    When I try really hard, I’m able to get like one or two bas during a fa

  • mike


  • U.N. Owen

    Wow! I’ve been coming to MOI for about 2 years (I just got an iPad, and am getting your app next week), and whenever I come here, I get stuck – looking at illusion-after-illusion.

    This is (for me) the first time I’ve learned something I’d never heard of before. It is bizzare, to say the least.

    I wonder if this McGurk effect can open a new door here – one to audio illusions. As I said, never heard of this effect, but, it’s fascinating.

    Thanks for sharing this.

  • SDER

    Wow, that is pretty cool. No matter how much I tried, if I looked at the guy, all I could hear was “va” but if I closed my eyes, I would only hear the same sound over and over again. It never ceases to amaze me how our brain works. Thanks again for this wonderful illusion.

  • Typeaux

    Amazing. I could not make myself hear “BAH” when it was visually clear that the mouth was saying “FAH,” even when I knew that the sounds I was hearing were identical. This is a very powerful effect. I only wonder what *practical* use it has in the real world and not in a study of effects.

  • Phillip

    Huh? What’s the illusion? He said bah and then he said fah? It’s hardly misheard lyrics. Like “i’m not talking about millennium” of “”Excuse me, while I kiss this guy”.

    • Dylan

      He he- nope, he didnt say FA- that’s the point- he was still saying FA- so obviously the illusion worked very well :)

  • notarealname

    I CAN DIFFER AND it sais fbaa fbaa wen he sais it at the same time the diferent pics
    but i can differ

  • Anbonymous

    … Very nice. I had heard of this, but had forgotten what it was called.

  • Eric


  • Yusif Azari


    I closed my eyes and the sound changed

  • Jackal

    That’s really awesome!! I can’t believe that our vision makes such a difference on our audio perception.

  • jazz

    I swear he is actually saying “FA” and their just messing with us

    • SDER

      If you close your eyes while he says “fa” you’ll notice that he actually does say “ba”.

  • shawn


  • Jeffrey

    I’ll be interested to see this taken to a new level. Right now, I’m mildly intrigued, but I didn’t think it was all that exciting.

  • Chris

    I thought it was stupid. She said the picture changed but you can still hear “ba”. I was like, “BA?! I hear freakin’ ‘VA’.” Then after a while I got what they meant. Cool illusion.

  • Mark Fain

    this one is pretty sweet.

  • wandering_goat

    This is the first time the effect’s worked on me, but even so, I can only sometimes hear “fa”. It’s almost always “ba”, especially if I’m focusing on the video. I was trained in music, so possibly that makes a difference in how well it works.

  • faith


  • morgan rowley


  • morgan rowley

    its true you hear ba instead of va if you close your eyes but it goes back to va if you open them again.weird.

  • me123987645

    that is so cool! i closed my eyes when he started saying (what seemed to be) fa and i heard ba. this is a really cool illusion.

  • kimbo


  • Ryan St. George

    Eye thing eye here “Baw” two! (Welcome to my world.)

  • brad

    Heh, love this!

    Is the audio at the beginning of the video the same as at the end? the audio sample i mean with the theme park rides and screaming?

  • miles

    thats fake close your eyes and listen

    • Dylan

      Sorry, but you probably didnt understand because its in no way faked- because you can control which you hear yourself by looking when you chose at one side or the other- or indeed closing your eyes when looking at the left image to stop hearing FA, and hear the correct BA whenever you choose to. And that IS the illusion.

  • http://www.aol.com Worldy Guy

    Instead of “fa” I hear “va”. But that could be because I know a lot of Yiddish speakers.

    • http://www.moillusions.com moe

      it dosent work for me either!!!!!!!!!!!!!
      i don’t hear baa in the second one, i hear va!

    • Kat

      If I concentrated really hard on the “B” of BAA when his mouth was going FAR I could hear BAA

  • http://www.facebook.com/people/Adam-Merrill/100002108047836 Adam Merrill

    Wow, this is great! I’d looked at this effect before, but this is the first one that actually worked! As an interesting sidenote, I noticed that if you look at the center of the two images (with one face saying “bah” and the other saying “fa” at the same time) and kind of view them both with your peripheral vision, it sounds like two people sboth saying each sound, and one (the “fa” I think) is slightly delayed! That’s amazing!!!

  • DanG

    wow…….. not just neat… but scary awesome. Black magic or something.

  • Dallas Valerian

    Wandering Goat’s mention of music’s influencing what is heard is funny as “fa.” Do, re, mi will do that I guess.

    My experience made me here “va” as the alternate, because I’ve noticed in Spanish speakers among South Americans that V as in Victor is pronounced Bictor as though it’s a B.

    A friend who spoke also fluent French confirmed this for me, asserting that in French his V was distinct from B but that in English, they were the same sound. Further, the confusion only goes in one direction. Not only does he say voulez, and not boulez, nobody ever asks the way either to el vaño or to the vathroom.

  • Padma

    I do not get this at all!

    • fossda

      listen to the voiceover in the video

    • Rich Pro

      If you look at your right of the screen, it is saying baa but if you look at your left of the screen, it looks like its saying faa,However, if you close your eyes,you hear baa again.(They just changed the picture. The picture,but not the sound.)

    • Suor de Sapo

      Me too! I hear the same on both…Bahh!!!

  • diggo

    It’s not all that dissimilar to the psychoacoustic phenomena used when designing lossy audio codecs such as MP3. Watch Poppy Crum’s segment in this video:

  • http://www.facebook.com/people/Sal-Salubrius/1452412946 Sal Salubrius

    I love this! I saw the whole BBC show when it was on and was so amazed that I went to the website to show my husband and watched it over again!

  • Zenbot

    In linguistics the only difference between an “f” and a “v” is that the “v” is vocalized, meaning you actually emit a sound from your throat when you say “vat” vs. just air from your throat when you say “fat.” Otherwise, the placement of the tongue and teeth against the lips are basically identical. I am not surprised some of you may perceive a “va” sound instead of a “fa” sound. I have also been told that when people are training to read lips they have to use a lot of contextual interpretation for issues like this, such as knowing the person probably wasn’t saying “It’s fairy nice to meet you.”

  • Dylan

    Glad you found this video cool- I knew you and everyone here would like it if you’d not seen it before. I have noted that if you dont focus enough on the left side on the split screen shots, it will muddy the FA closer to the real BA.

  • Jeannine

    this is one of the coolest illusions I have ever seen – I had to immediately email it to my friends! Almost scary…

  • B_man


  • sally

    Osama….obama….osama…..obama….osama….obama….Cool! Almost the same.

  • wow

    try saying island view in the mirror silently..
    crazy how our minds work

  • http://www.idcredit.org/ Eric

    Brendan, never get a tattoo

  • http://www.paydayloantruth.org/ Glen

    The most interesting part about this is stated in the video: No matter how much you know about it, it still works. Almost all other illusions go away once you know the mechanics behind it.

  • http://www.weightlossdietpills.org/ Kyle

    Not exactly an illusion. I just spent a Semester on the Science of Speech sounds, it would take a while to explain what exactly is happening but essentially its a combination of human articulation sloppyness (lack of Invariance) and our brain trying to make sense of things contextually. Top Down preprocessing in action

  • Bill

    If your teachers had done a better job of teaching you pronunciation, there would be no effect.

  • Michael Carabini

    .This video demonstrates how looking at someones mouth movements affects the way we hear what they are saying. The man in the video is saying bah bah bah but when the same audio recording is played while he mouths out fah fah fah it sounds like he is saying fah fah fah. ..

  • Penny

    Close your eyes people!!

  • rajat

    stupid illusions!!!!!!!!!!!!!!!!!!!!!!!

  • Meghan

    The narrator doesn’t stop talking long enough for me to hear it. I only heard ba. Also, I knew that the noise was ba even when the image changed, and I still heard ba. Maybe if I wasn’t being told about this effect the results would have been different.

  • the man

    i didnt get any thing….wait!!! i think he is calling his father



  • dan

    if you close your eyes on the VA one…it will say BA. but what you see is what you hear. so if you don’t look you will hear correctly. when you close your eyes your hearing increases.

  • http://egrojsoft.info/ EgRoJ

    Incredible, I saw the video without sound, I guess the word is “PAAAAM”, and the second “BIIIIRD”. lol

  • jgfhjgf

    the narrator was too much talking!

  • tiny

    It doesn’t work for me. I know that I am supposed to hear first ‘bah-bah’ and then ‘fah-fah’, but I keep hearing ‘bah’, even when I consciously try to hear ‘fah’.

  • C-c-c-combo

    So what if you hear Bah? I figured out you can make a good enough -b- sound while still looking like you’re saying -f-. Since I figured that out all I can hear is bah.

  • saman

    good web

  • Zeb

    I think it would have looked better with a sexy girl’s lips doing it. When children are in speach class they are taught to look at the taechers lips to see the sound she is making, or some people learn to read lips. the sounds are almost the same, when you have one of those ABC toys that say the letter V and B sound the same.

  • jake

    I heard the Yamaha “I wanna ride” ad, and silently I moved my mouth to say “I wanna Fly”

    then it sounded like the ad was saying “i wanna fly”


  • Andy

    And this guy is a PROFESSOR?… It’s obvious for every phonetician that plosive consonants make unique “shock waves” recognized by our hearing, as opposed to the VAH. That’s not an illusion.

  • Kip

    I find the narrator speaks only when he’s doing the Fah and never the Bah. Even if I don’t watch the video I hear an F. I’m not sure if it’s because I’ve already seen it, but it’s generally when the narrator has spoken over the other sound.

  • Shane

    I’m deaf in one ear, so the hearing in my good ear is heightened, so it didn’t work for me. Although the theory is there, the practice didn’t work. It’s very similar to a prank my dad used to do on me. I’d be eating an orange or banana and he would come over and put an onion under my nose. after that, everything I ate tasted like onions. THANKS DAD!

  • AmetuerAspirant

    this is just baffling, though after most of the video, and concentrating very fiercely on the sound while watching, i was actually able to make the “vah” mouth make a sound vaguely b’ish. then the narrator started talking over and i couldn’t hear the sound well enough to do it. thank you a lot annoying British narrator…

  • Dem



  • Joex

    Reminds me of the seagulls in finding nemo…. lol…

  • zoakera

    Why cant i download or hear it using my mobile phone???
    Can anybody helppp
    plzzzzzz. . . . .

  • L.J

    I heard the “Vah” thing from the start with my eyes open. I have keen hearing and I had to lean Spanish. I’ve got used to “b” and “v” sounds.

  • Natalia

    This seems so silly to me. The only example they could show was “ba” vs. “va,” which are such similar sounds anyway. If one’s teeth are close together and make a good seal, and one tries to make a sudden or hard “v,” the way the sounds are made, and thus the sounds too, are almost identical. Of course, you are going to choose the one it looks like he’s saying. Sheesh. They should show a lot more examples if they are going to use this to illustrate a whole concept.

  • Chloe

    I can hear ‘PA’ and then ‘PVAH’ — ?!?

  • Tommy G Starfire

    Have you any wool?