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Krulwich Wonders: What's He Saying? 'Bahh' Or 'Fahh'? A Brain Mystery

Friday, September 23, 2011 - 02:05 PM


I love illusions, where your brain makes weird things happen. Those of you who come here often have seen some doozies, but this one ... oooh, this is one of the strangest.

The question is: Which is more powerful, your eyes or your ears? Watch this clip and experience "The McGurk Effect." Your ears will feel ashamed.

Source: YouTube

The McGurk Effect is named for a psychologist from Scotland, Harry McGurk, working with John MacDonald. The experiment shows that while our senses seem separate — you wouldn't think what you see should affect what you hear — it turns out, that's totally wrong. If our eyes see one thing and our ears hear a different thing, when sight and sound grapple in our brains, the eyes win. Eyes tell ears what to hear. Or so it seems.

Not only that, even if your brain knows this is an illusion, you still can't hear the truth unless you close your eyes. The illusion is that powerful.

Why Does This Happen?

Does sight always beat sound? Professor Lawrence Rosenblum in the video seems to suggest that experimental results may vary depending on which sense is "more salient." I'm not sure what that means. Nosing around, I found some experiments where you see lips saying "gah" while the sound is saying "bah" and my brain chooses neither of them, and settles for a middle-of-the-road "dah." But nowhere could I find an explanation for why my ears keep surrendering to my eyes.

Does anybody know?


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Comments [7]

Ayo from Minneapolis, MN

Well, I think as Humans we tend to create an experience from what we EXPECT from our observations. We know that the visual experience should reach our brain first, and it's safe to say that this split-second could be quite the implication for the brain's general synthesis of experience. The rest of the experience may have to fall in line behind our brain's sort of "predictive" model.

Jan. 11 2012 12:26 PM
coolgirl20 from ealing

hi! this was brill,how did you make it find out this./ Not true excuse me while i puke for a week in the toilet rubbishhhhhhhh.fuc this crap

Jan. 10 2012 02:37 PM
coolgirl20 from ealing

fuc this rubbish website

Jan. 10 2012 02:33 PM
coolgirl20 from ealing

that was rubbish also it dosen't even make sense,working on something for 25 years and hardly knowing anything about it - means nothing it shoudnt even be on the internet.

Jan. 10 2012 02:30 PM

I think Sophie Molholm has the answer, or at least she is working on it. I recently went to a lecture she gave about the differences between how neuro-typical children process visual and auditory information and how the brain "integrates" the two compared to children with autism. She used "The McGurk Effect" to demonstrate integration. I think you can find her at Albert Einstein College of Medicine. I also think she was on All Things Considered.

Nov. 19 2011 08:24 AM
TBS from NYC

Some researchers are trying to harness this cross-talk between visual & auditory systems to help the blind -

Sep. 28 2011 02:45 PM

Rosenblum says it's about salience, so maybe the thought I'm having has been disproved, but I wonder if the effecy reflects that we interpret what we see a little faster or sooner than what we hear. Then it's not because visual information is weightier because it's vision, but dominates only because it arrives first, and our brain does not change it's theory of what's happening on the fly--or can not do it least within intervals short as between sight of an utterance and the sound of it. This interval might be close to the size of an atom of experience, in other words.

I suppose there's a comparison to be made to the speeds or durations of backward masking and other perceptual oddities of very fast happenings. McGurk might not be even in the same ballpark. (Sound takes about 4 milliseconds to travel 4 feet from lip to ear, I reckon).

Diminishing brightness actually slows how fast we perceive what we're looking at (it's a reason we're advised to drive more slowly, I suppose), which suggests an experiment to test whether it's about sequentiality vs salience. Maybe sight is never slower than hearing though.

Sep. 25 2011 05:24 PM

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