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"Perceptible Difference" -- The Discovery Files

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Results of a new study involving macaque monkeys suggest that speech and music might have shaped the human brain's hearing circuits. Using functional magnetic resonance imaging (fMRI), researchers monitored the brain activity of macaques and healthy human volunteers and how it responded to harmonic sounds, or tones. Humans were more sensitive to pitch, a key component of speech and music, than were the macaques.

Credit: NSF/Karson Productions

Audio Transcript:

Do you hear what I hear?

I'm Bob Karson with the Discovery Files, from the National Science Foundation.

You're playing one of your favorite jams for your macaque monkey and he's like, "meh." Before you think he's lost touch, you might wanna check a multi-institution study on macaques' perception of sound and how it's processed in their brains compared to human brains.

To measure brain responses in both, fMRI or functional magnetic resonance imaging was used, to scan for activity in certain areas of the brain as it happens. Various sounds were played two ways: Example a normal macaque call: (Sound effect: sound :03) Then the team digitally removed the tonal qualities of the same sound. (Sound effect: sound :03)

Result: The brains of the humans were much more responsive to the pitch quality of the calls than were the brains of the macaques themselves. Humans showed a stronger preference and sensitivity for sounds with pitch -- the kind of sounds we hear in speech or music -- suggesting those sounds may have shaped the development of the human brain's hearing circuits. The monkeys may see what we see, but they seemingly do not hear what we hear and may experience music and other sounds differently.

Guess that means your macaque won't be complaining that your singing sounds (Sound effect: monkey screech) "pitchy."

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