Weird Fact #22: Your eyes can cause your ears to hear things that aren’t there.
There’s a great old line that most of us have used at one point or another in the heat of an argument: “Who am I going to believe? You or my own ears?”
After your mind is completely blown by today’s weird fact, you might never ask that question again or at least you won’t be sure of the answer.
First, a little background. Many years ago a researcher named Harry McGurk was testing the effects of mothers’ voices on their babies because… well…because scientists lead boring lives. At one point McGurk redubbed the voice of a mother saying one syllable over video of her saying a similar but different syllable. At first glance, the result would seem to be something like one of those hilariously retranslated kung fu movies. But oddly McGurk heard something pretty similar to the sound he saw the woman say, NOT the sound he actually redubbed. It was so bizarre that his first thought was to recheck the tape. But it was playing correctly. His ears however were not hearing it correctly. Instead, he was hearing something closer to what his eyes told him she was saying.
What McGurk had accidentally stumbled upon remains among the most extraordinary audio/visual illusions I’ve ever experienced. He published it in a paper called “Hearing Lips and Seeing Voices.”
Now, if you are tired of people “bahing” “gahing” at you like you are a five-month-old, you might take a brief moment to think about the awesome implications of this perceptual effect and why it is so utterly freaky. It’s not just your conscious mind making the assumption that the syllable is what’s shown. You ACTUALLY hear the other syllable or at least some middle “compromise” syllable that your brain has decided upon. By simply closing your eyes, you will hear something completely different. Open them and the sound will change back.
We tend to think of our senses as separate feeds of raw information pouring into our pre-frontal cortex but they are not. What you think you see and hear is actually filtered and combined into a single coherent whole before it ever reaches your consciousness and its adjusted along the way for your listening and viewing pleasure. This is why, no matter how hard you try and no matter how much you know about the effect, you can’t hear the real syllable being said as long as your eyes see something else. Your brain simply won’t allow it because it doesn’t make sense. At an unconscious level, it alters the sound for you so what you are seeing syncs up with what you are hearing and it does this even if you consciously know what the real sound is and what you should hear. Your eyes still override your ears and send you a false message.
Before you are too hard on your brain for blatantly getting caught in a lie like this, you should remember that it is the result of millions of years of evolution, most of which took place well before the invention of video tape that psychologists could redub to fool babies (or other psychologists). In fact, your brain is just doing what it is supposed to do. It knows that lips which make a “gah” or “dah” shape shouldn’t sound like “bah” so it assumes, not unreasonably, that your ears made an error, one which it helpfully fixes for you.
But the very fact it can correct this error and change the sound before you mentally “hear” it is simply incredible. Like Neo in “The Matrix,” we are left to question whether what we are seeing and hearing is actually reality and we don’t even need the pain of having that creepy prong shoved into the back of our cerebellum — nor the even worse agony of watching Keanu Reeves attempt to convey human emotion.
The fact is that your brain lies to you every day. The theater of the mind shows you not what your senses perceive but an overall picture it develops for you based on the best information available.
And if there are any parts that don’t seem to make sense?
Well, those wind up on the cutting room floor.