The ability to distinguish between sounds of varying pitch makes people capable of producing and understanding speech and music. And the way we are able to process pitch has been thought to be unique to our big-brained species.
But now, there’s evidence that a tiny monkey—the common marmoset from Brazil—can distinguish pitch the same way we do. That’s according to a study in the Proceedings of the National Academy of Sciences. [Xindong Song et al, Complex pitch perception mechanisms are shared by humans and a New World monkey]
Ten years ago, researchers identified a region of the marmoset brain that appeared to process pitch. But they needed to confirm that the animals did indeed notice changes in pitch—which presented a challenge: they had to find a way to get the animal to indicate that it had heard something. So they trained the marmosets to respond to a change in pitch with a behavior—specifically, they would lick a waterspout.
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The researchers then had the animals listen to a series of notes with the same pitch. And, at random, they’d change it up. “Just like, for example, when I say, ‘ma ma ma MA.’ Right, at some point I make the pitch a little higher.” Johns Hopkins neuroscientist Xiaoqin Wang, lead researcher of the study. The actual difference in pitch, he says, was much smaller than that. But you get the idea. “And, when the animal hears that change, it will lick the waterspout to indicate they hear the difference.” Which the miniscule monkeys indeed did.
Because both we and marmosets have this talent, the ability likely evolved in a common ancestor long-ago—this type of pitch perception may thus go back more than 40 million years ago, much earlier than previously thought. And the understanding of how the brain processes pitch may eventually explain why some people have perfect pitch, while others are tone deaf.
—Christine Herman
[The above text is a transcript of this podcast.]
