The McGurk effect is a phenomenon that demonstrates the interaction between the ears and the eyes in speech perception. You can try the experiment yourself using three short video clips.

With the first clip, make sure that the sound on your computer is turned up. Play the clip but do not (I repeat, do not) look at the screen.

• Click here to watch the first clip.

What sound did you hear?

Now turn the sound on your computer down. Watch the second clip and try to lip read the man. What sound is he producing?

• Click here to watch the second clip.

Finally, turn the sound on your computer back up. Now watch and listen to the final clip and again try to identify the sound that is being produced.

• Click here to watch the third clip.

Results

1. In the first clip (audio), the sound that is being produced is ba-ba
2. In the second clip (vision), the man’s lips are saying ga-ga
3. In the third clip (perceptual), things aren’t so straightforward. The most likely sound that you think you heard is ga-ga

In case you didn’t guess, the three clips are identical. This auditory illusion is explained by Dr John Medina:

Personally, I don’t think that the man in Dr Medina’s video demonstrates the effect well - his mouth doesn’t articulate the ga-ga sound very convincingly and the effect is lost on me. But I like Dr Medina’s explanation and I have used it in the lesson plan below.

the-mcgurk-effect.pdf

A couple of interesting facts that I found about the McGurk effect on Wikipedia:

• The effect is very robust; that is, knowledge about it seems to have little effect on one’s perception of it. This is different from certain optical illusions, which break down once one ’sees through’ them.

• Study into the McGurk effect is being used to produce more accurate speech recognition programs by making use of a video camera and lip reading software.

Posted by admin on Sunday, February 22nd, 2009 at 1:51 am.