You hear with your eyes and see with your ears


It is common knowledge that we see with our eyes, hear with our ears, taste with our tongue and smell with our nose.


But it isn’t true. In the Seventies, Harry McGurk and John MacDonald stumbled on a curious but important effect. They dubbed the syllable ba onto a video of a girl mouthing ga. When they watched the video, they clearly heard the syllable da.


They weren’t taking anything, and the effect wasn’t caused by too many late nights: we’re all fooled by it. There are internet videos with this effect. When you close your eyes and watch them, you’ll hear the syllable ba. When you open your eyes you won’t hear one thing and see another: you’ll clearly hear the syllable da. Knowing about the trick and how it is caused won’t make it go away.


In the opposite direction, the information that reaches your ears can change what you see. When a single flash of light is accompanied by a series of beeps in quick succession, we see multiple flashes of light.


We have the impression that we piece the world together in consciousness. We have the illusion that we see and hear things through our senses. But in fact, the world is interpreted long before we’re aware of it. Not only does consciousness not combine the information from our senses, it doesn’t even know which senses are providing the information


Dr Chris Paley is the author of Unthink, which has been published in six languages.

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