Humans are not
the only primates with the capacity for speech. Koko the gorilla
understands a silent form of communication, American Sign Language.
At The Gorilla
Foundation, where Koko has spent more than 40 years living immersed with humans
-- interacting for many hours each day with psychologist Penny Patterson and
biologist Ron Cohn, she is performing amazing vocal behaviours.The vocal
and breathing behaviors Koko had developed were not necessarily supposed to be possible.
And the
particular vocal repertoire of each ape species was thought to be fixed. They
didn't really have the ability to learn new vocal and breathing-related
behaviours.
These limits fit a theory on the evolution of language, that the human ability to speak is entirely unique among the nonhuman primate species still around today.
In a study published online in July in the journal Animal Cognition, Perlman and collaborator Nathaniel Clark of the University of California, Santa Cruz, sifted 71 hours of video of Koko interacting with Patterson and Cohn and others, and found repeated examples of Koko performing nine different, voluntary behaviors that required control over her vocalization and breathing. These were learned behaviors, not part of the typical gorilla repertoire.
Among other things, Perlman and Clark watched Koko blow a raspberry (or blow into her hand) when she wanted a treat, blow her nose into a tissue, play wind instruments, huff moisture onto a pair of glasses before wiping them with a cloth and mimic phone conversations by chattering wordlessly into a telephone cradled between her ear and the crook of an elbow.
"She doesn't produce a pretty, periodic sound when she performs these behaviours, like we do when we speak," Perlman says. "But she can control her larynx enough to produce a controlled grunting sound."
Koko can also cough on command -- not particularly groundbreaking human behavior, but impressive for a gorilla because it requires her to close off her larynx.
"The motivation for the behaviors varies," Perlman says. "She often looks like she plays her wind instruments for her own amusement, but she tends to do the cough at the request of Penny and Ron."
These behaviors are all learned, Perlman figures, and the result of living with humans since Koko was just six months old.
"Presumably, she is no more gifted than other gorillas," he says. "The difference is just her environmental circumstances. You obviously don't see things like this in wild populations."
This suggests that some of the evolutionary groundwork for the human ability to speak was in place at least by the time of our last common ancestor with gorillas, estimated to be around 10 million years ago.
"Koko bridges a gap," Perlman says. "She shows the potential under the right environmental conditions for apes to develop quite a bit of flexible control over their vocal tract. It's not as fine as human control, but it is certainly control."
Orangutans have also demonstrated some impressive vocal and breathing-related behavior, according to Perlman, indicating the whole great ape family may share the abilities Koko has learned to tap.
These limits fit a theory on the evolution of language, that the human ability to speak is entirely unique among the nonhuman primate species still around today.
In a study published online in July in the journal Animal Cognition, Perlman and collaborator Nathaniel Clark of the University of California, Santa Cruz, sifted 71 hours of video of Koko interacting with Patterson and Cohn and others, and found repeated examples of Koko performing nine different, voluntary behaviors that required control over her vocalization and breathing. These were learned behaviors, not part of the typical gorilla repertoire.
Among other things, Perlman and Clark watched Koko blow a raspberry (or blow into her hand) when she wanted a treat, blow her nose into a tissue, play wind instruments, huff moisture onto a pair of glasses before wiping them with a cloth and mimic phone conversations by chattering wordlessly into a telephone cradled between her ear and the crook of an elbow.
"She doesn't produce a pretty, periodic sound when she performs these behaviours, like we do when we speak," Perlman says. "But she can control her larynx enough to produce a controlled grunting sound."
Koko can also cough on command -- not particularly groundbreaking human behavior, but impressive for a gorilla because it requires her to close off her larynx.
"The motivation for the behaviors varies," Perlman says. "She often looks like she plays her wind instruments for her own amusement, but she tends to do the cough at the request of Penny and Ron."
These behaviors are all learned, Perlman figures, and the result of living with humans since Koko was just six months old.
"Presumably, she is no more gifted than other gorillas," he says. "The difference is just her environmental circumstances. You obviously don't see things like this in wild populations."
This suggests that some of the evolutionary groundwork for the human ability to speak was in place at least by the time of our last common ancestor with gorillas, estimated to be around 10 million years ago.
"Koko bridges a gap," Perlman says. "She shows the potential under the right environmental conditions for apes to develop quite a bit of flexible control over their vocal tract. It's not as fine as human control, but it is certainly control."
Orangutans have also demonstrated some impressive vocal and breathing-related behavior, according to Perlman, indicating the whole great ape family may share the abilities Koko has learned to tap.
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