Language Affects Sound Perception

This post originally posted here.

by Noiseman433 on Sat Dec 20, 2003 1:17 pm

I’ve always thought this was the case, nice to find some research has been done with it.

NEWPORT BEACH, CALIFORNIA–Neuropsychologists may owe a debt to the devil. At the 140th meeting of the Acoustical Society of America here last week, University of California, San Diego, psychologist Diana Deutsch demonstrated that an auditory illusion based on the tritone–also known as the “devil in music”–is perceived differently by listeners with different linguistic histories. And those perceptions might help psychologists understand how the brain rewires itself during childhood.

Played together, two notes a half-octave apart (such as C and F sharp) sound jarring; medieval musicians considered this combination, a tritone, so discordant that they dubbed it the “diabolus in musica.” But a tritone is music to Deutsch’s ears. For more than a decade, she has been studying an auditory illusion–the acoustical equivalent of an optical illusion–based upon the tritone.

With a computer, Deutsch created ambiguous notes by superimposing tones from many octaves and carefully shaping the relative loudness of the higher and lower frequency components, masking how high or low the note is. Although listeners can perceive one of these notes as, say, a C, they can’t tell its octave, whether high C, middle C, or low C. Indeed, the tone doesn’t really belong to any octave at all.

Things get interesting when people compare tritone pairs of ambiguous notes, such as an ambiguous C with an ambiguous F sharp. Even though neither note is higher or lower than the other–because higher and lower don’t have any meaning with ambiguous notes–people consistently perceive one tone as high and the other as low. But strangely, they don’t agree which is which. “The musical illusion is perceived very differently by different people,” says Deutsch. This is the tritone paradox.

Things got even weirder when Deutsch played ambiguous tritones to different groups of people. In 1992, she noticed that people from California and people from Southern England hear tritones in the opposite way; if a Californian thinks that a C is above an F sharp, the Britisher will swear that the F sharp is higher than the C. This led some psychologists to believe that a person’s perception of ambiguous tritones depends strongly upon the intonations of the language he learns as a child. Since then, psychologists have been trying to prove it.

At the Acoustical Society of America’s meeting last week, Deutsch described her latest experiment, in which she played ambiguous tritones to two groups of subjects who had emigrated to California from Vietnam. The first group came to the United States as children, and although Vietnamese was their first language, most no longer spoke it fluently. The second group, on the other hand, arrived in the United States as adults and spoke little English. The two groups perceived the tritones in the same way–but differently from their California neighbors. “This study presents strong evidence, we believe, that individual differences [in perceiving the tritones] are caused by individual speech patterns to which [the subjects] are exposed early in infancy,” says Deutsch.

“It reinforces the idea that early linguistic background affects perception,” says Magdalene Chalikia, a psychologist at Minnesota State University in Moorhead, who has shown that Greek speakers and English speakers perceive tritones differently. The tritone paradox gives neuropsychologists intriguing hints about the effects of training on the brain. The results suggest that as an infant learns its first language, the brain may adjust its neural connections in a way that affects the perception of sounds. But for the moment, scientists have little idea which languages cause which interpretation of the tritone paradox, much less how each language rewires the brain differently. “You can’t make predictions,” sighs Chalikia. “It’s frustrating.” The devil, it turns out, is in the details.


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