HUMANS ARE NOT ALONE IN OUR EAR FOR PITCH BECAUSE MARMOSET MONKEYS SHARE OUR UNIQUE PERCEPTION ABILITIES

HUMANS ARE NOT ALONE IN OUR EAR FOR PITCH BECAUSE MARMOSET MONKEYS SHARE OUR UNIQUE PERCEPTION ABILITIES

Human’s ears apparently aren't alone in the ways we perceive pitch. A Johns Hopkins study finds evidence that marmoset monkeys share distinct features with human in the way they distinguish between high and low notes.

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The research sheds light on the evolution of vocal communication or song, suggesting that aspects of pitch perception might have developed over millions years ago. A summary of the findings was published this week in the Proceedings of the National Academy of Sciences.

Though pitch perception has been found in other animal species, human’s ears have always stand out as unique in their specialized abilities. "We didn't think any animal species, including monkeys, perceived it the way we do," says Xiaoqin Wang, professor of biomedical engineering at the Johns Hopkins University School of Medicine. "Now we know that marmosets, and likely other primate ancestors, do."

Marmosets, small monkeys native to South America, are known as highly vocal and social creatures. A decade ago Wang and his research team explored that the monkeys are able to process pitch. They located a region in the marmoset brain where nerve cells "fired" after exposure to sounds with pitch, like a melody's shift from high to low notes. Human brains show similar activity in that region, Wang notes.

What researchers were missing, though, was behavioral evidence that the marmosets could perceive and respond to pitch in the same way humans do. Wang's team spent years developing ways to test that.

They find out that marmosets share the three specialized features of pitch perception once thought to be unique to human’s ears.

-      - Marmosets are better at distinguishing pitch at low frequencies rather than high.

-     - Marmosets are able to pick up on subtle changes in the spread between pitches at low frequencies.

-      - Marmosets' sensitivity to rhythm appears to dictate their ability to detect pitch differences among simultaneous tones.

Wang says it's possible these specialized abilities with pitch evolved in ancient marmosets over millions years ago.

On top of the evolutionary implications of this study, Wang says "now that we have a primate relative we can study behaviorally and physiologically." Such research, he says, could investigate tone deafness and whether perfect pitch is a learned trait or inherited.

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