Chatty Marmosets Have Something To Say About Vocal Learning
MELISSA BLOCK, HOST:
Robert, let's try a quick experiment here.
ROBERT SIEGEL, HOST:
BLOCK: See if you can make this mouth sound. (Making squeaky sound).
SIEGEL: That's easy for you to say.
SIEGEL: (Imitating squeaky sound). Not very well.
SIEGEL: E for effort, Robert. Well, it turns out that imitating sounds is something that humans are really good at. It's part of what makes us special. And NPR's Geoff Brumfiel reports that researchers now think a species of monkey might possess similar skills.
GEOFF BRUMFIEL, BYLINE: Learning to make sounds by listening to others is called vocal learning, and there's just a few species that can do it - mostly birds and humans. Now, don't get me wrong, chimpanzees are smart. They can learn some sign language, but they can't learn to talk.
ASIF GHAZANFAR: We didn't think that mammals - and primates in particular - besides us actually had any type of vocal learning.
BRUMFIEL: Asif Ghazanfar is at Princeton University. Now research he's published in the journal Science suggests there's at least one species of monkey that might be able to learn vocally, the common marmoset. Marmosets aren't your typical primate. They're tiny with big, round eyes and long, fluffy tails.
GHAZANFAR: They're cute and they smell. They wash themselves in their own urine. I'm not sure why they do that.
BRUMFIEL: But Ghazanfar says once you get over the smell, these little guys are interesting. Marmoset mommies always give birth to twins and they need help raising them, so everyone gets involved.
GHAZANFAR: The father sticks around and helps take care of the offspring. Moreover, older siblings will help take care of younger siblings and group members that are unrelated to those infants will also help out.
BRUMFIEL: Sound familiar? That's how humans do it. Ghazanfar thinks all the child care is what gives marmosets another special trait - they're super talkative.
(SOUNDBITE OF MARMOSET CHIRPING)
GHAZANFAR: They're chattering nonstop, and that is also very different from our close relatives, the chimpanzees.
BRUMFIEL: To see if all that yammering was passed on from parents to babies, Ghazanfar devised an experiment.
GHAZANFAR: Almost every other day, we simply took one of the infant marmosets, and for a very brief time, we separated it from its parents and then recorded its vocalizations.
(SOUNDBITE OF MARMOSET INFANT CHIRPING)
BRUMFIEL: The very young infants made low, raspy sounds - not your typical marmoset chatter.
GHAZANFAR: It kind of has this rough, noisy characteristic to it.
BRUMFIEL: But over time, that changed.
GHAZANFAR: When they reach about two months of age then they're going to produce these very kind of clear, whistle-like calls.
(SOUNDBITE OF MARMOSET CHIRPING)
GHAZANFAR: They really are annoying, unfortunately.
BRUMFIEL: The amount of time it took to go from the low, rough call to that high squeak depended on how much feedback the baby marmosets were getting from their parents. In other words, the marmosets were learning through listening, vocal learning.
Erich Jarvis studies vocal learning in birds like parrots at Duke University. He says there's been a long-held view in science that when it comes to learning how to imitate sounds...
ERICH JARVIS: You have it and you don't have it. And humans and parrots are the haves and nonhuman primates are the have-nots.
BRUMFIEL: This new work shows that's probably not the case. The marmosets are able to pick stuff up, though Jarvis still isn't convinced that this learning is as complex as what humans and birds can do.
JARVIS: There is something in between, all right? Not necessarily black and white, but a continuum.
BRUMFIEL: Both researchers agree that studying marmosets could be useful for us humans. Because we're both social primates, these little monkeys might be able to provide clues about human disorders that make learning language difficult. Geoff Brumfiel, NPR News. Transcript provided by NPR, Copyright NPR.