Pay attention to the first seconds of the following video. Depending on what you are thinking, depending on what your brain is focused on, you may hear one phrase or another. The phrase will always be the same, but every time you listen to the video you will hear a different phrase if you change your thought.
It's not a Matrix bug. It is not magic or witchcraft. It is just one more example of how sloppy our brains sometimes are, and that evolution is blind and random. Welcome to McGurk effect: what researchers call a 'perceptual phenomenon' and which arises from a mismatch between sound and visual signals.
Bike or Rental?
Before watching the following video, think about the word "bike" or "rental." Every time you play it, you will hear one word or another, just changing your thinking:
He McGurk Effect suggests that, in a multisensory conversation (that is, in which information reaches us from different senses), the brain is governed by a principle of 'causal inference'. From a pair of syllables, one visual and the other auditory, the brain calculates the probability that they come from the same speaker, and based on that one sound is perceived and another. That's why in the video you can hear "bike" or "rental" depending on whether you are thinking of one word or the other.
Michael Beauchamp, professor in the Department of Neuroscience at Baylor College of Medicine, explains the McGurk effect in a study: If we visually see lips pronouncing the syllable 'ga' and simultaneously hear the sound 'ba', our brain will 'hear' the 'da'. That is, what the eyes see can change what the ear perceives.
If you want to feel the magic again, here is the video again (sometimes the effect is not as powerful if you use headphones, by the way):
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The news
Every time you watch the following video you will hear something different even if nothing changes: the McGurk effect
was originally published in
Xataka Science
by
Sergio Parra
.