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. Ten years ago, researchers identified a region of the marmoset brain that period 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. The researchers then had the animals listen to a series of notes with the same pitch.