They say that seeing is believing, but sometimes an optical illusion causes us to see what isn’t there. The same is true for musical illusions, which cause us to hear what isn’t there. Listen to one musical illusion and find out what it tells us about the infant brain.
A 'noteworthy' finding. I'm Bob Hirshon and this is Science Update.
For years, psychologist Diana Deutsch of the University of California at San Diego has been studying a musical illusion called the tritone paradox. Listen carefully to these two notes.
Was the second note higher or lower than the first?
It turns out that the tones are constructed so that neither answer is correct, but some people insist the second note is higher, while others report the opposite.
Deutsch thinks that the way we perceive the paradox depends on the language we heard as infants. Recently, she studied a group of adults who had come to the United States from Vietnam as children.
"...who had been exposed to one language in infancy, and later acquired a different language. Would such people hear the tritone paradox in accordance with their first language, or would they hear it in accordance with the language which they now speak?"
The researchers found these young adults heard the paradox the way fluent Vietnamese speakers did, despite not having spoken the language since early childhood. So Deutsch says this musical illusion's more than just a curiosity. It shows how our mother tongue leaves a lasting imprint on our brains.
For the American Association for the Advancement of Science, I’m Bob Hirshon.
Making Sense of the Research
According to Webster's New World Dictionary, an illusion is defined as:
"an unreal, deceptive, or misleading appearance or image; a false conception, perception, or interpretation of what one sees; or the misleading image resulting in such a false impression."
As most of us probably would imagine, this definition centers on a visual image. Illusions, in fact, are most commonly known as optical illusions. There are a wealth of books, pictures, posters, and websites that deal solely with these optical illusions. The famous endless staircase and the impossible triangle are both examples of optical illusions.
It's not hard to think up numerous examples of optical illusions. But how many auditory illusions have you come across? Auditory illusions differ in that our brains trick our ears, not our eyes. They are much less common, but they do exist. As you just heard, this Science Update looked at the tritone paradox, which is produced when two notes, related by a half-octave, are played in succession. Those hearing the two notes may have very different perceptions of which note is higher. It seems that our perceptions of auditory illusions are as individual as we are!
As William James, psychologist, wrote: "While part of what we perceive comes through our senses from the object before us, another part (and it may be the larger part) always comes out of our own mind."
Now try to answer the following questions:
- What is the name of the musical illusion studied by psychologist Diana Deutsch?
- Which note did you think was higher, the first or second?
- Which answer is correct? What might influence how we hear these two notes?
- Ask your classmates which note they thought was higher, then ask them if they or their parents speak another language. What were your results?
- Can you come up with any other auditory illusions, which may in fact be influenced by our heritage?
One great optical illusion site is Sandlot Science. Here you can learn the secrets behind optical illusions and try some for yourself.
To learn more about the tritone paradox, and to hear examples, visit Tritone Paradox.