Brain: Heard and Misunderstood

Every kid has played with optical illusions, such as the silhouetted vase that turns into two opposed faces. Equally bizarre but much less familiar are the tricks that can be played on the ears. Perceptual and cognitive psychologist Diana Deutsch of the University of California at San Diego has cataloged dozens of perplexing aural illusions and collected 18 of them on a CD, Phantom Words and Other Curiosities.

PT: Why is it so easy to fool your ears?

DD: The auditory system has to make do with pitifully little in the way of information. The brain has more than 100 million receptors in each eye. The ear has only 16,000.

On one track, a short spoken phrase is looped, and after a few repetitions, it begins to sound like singing rather than speech. Why does that happen?

Speech and music are much more connected than people are willing to accept. When listening to people speak a foreign language, it often sounds musical. The part of the brain trying to process it as speech gives up, and the pitches come through. We don't normally hear all speech as if it were sung, but in terms of general acoustical theory, we should.

Why is it so fun to play with these illusions?

Well, it's so surprising! It's like a magic show. But some people find it distressing. We like to believe that when we perceive the world, we're correct in our perceptions.

Deutsch's recordings can be heard at philomel.com.

Tags: auditory system, aural illusion, cognitive psychologist, diana deutsch, dozens, ears, foreign language, hearing, illusion, language, magic show, music, optical illusions, part of the brain, perceptions, phantom, pitches, receptors, repetitions, speech, spoken phrase, university of california, university of california at san diego, vase

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