An ape, directly socialized with humans, has learned the vocal and breathing control found in human speech, according to new research.
Koko the gorilla, famous for her ability communicate with her keepers using American Sign Language, has also developed breathing and grunting patterns associated with the ability to talk – something scientists thought to be impossible in her species.
Postdoctoral researcher Marcus Perlman at the University of Wisconsin-Madison and Nathaniel Clark at the University of California studied 71 hours of video footage of Koko interacting with her keepers and identified vocalizations thought to be impossible for gorillas.
The researchers say that they have "found examples of Koko performing nine different, voluntary behaviors that required control over her vocalization and breathing." The 44-year-old ape's sign-language training began in 1972, and she has spent most of her life working with humans.
According to the paper published in the July issue of "Animal Cognition," video records show Koko huffing and grunting into a telephone, huffing on the lenses of eyeglasses, performing a fake cough, blowing her nose, performing her version of a ‘raspberry’ (folding her tongue lengthwise and blowing air through it), and blowing into her hand as a communicative gesture.
The researchers say that these recorded signs suggest that under certain circumstances, apes are able to develop flexible control over their breathing, and that they can use this control to perform attention-getting vocalizations and socially transmitted, learned behaviors like whistling.
"These were learned behaviors, not part of the typical gorilla repertoire," the scientists concluded
"She doesn’t produce a pretty, periodic sound when she performs these behaviors, like we do when we speak. But she can control her larynx enough to produce a controlled grunting sound," Perlman said.
"Koko bridges a gap. She shows the potential under the right environment conditions for apes to develop quite a bit of flexible control over their vocal tract," he explained. "It’s not as fine as human control, but it is certainly control."
In the 1930s and 40s, researchers raised chimpanzees alongside human children, attempting and failing to teach them to speak. Ever since, says Perlman, scientists had accepted "that apes are not able to voluntarily control their vocalizations or even their breathing" – until now.
In another recent study, research showed that bonobos communicate with high-pitched calls that require context to understand – much like human babies do. The findings were hailed as capable of providing valuable new insights into how humans developed the ability the use language to communicate.
The lead author of the bonobos study, Dr. Zanna Clay, commented that "the more evidence we gather from studies of our great ape relatives, such as bonobos, the more we learn that many capacities thought to be uniquely human actually have their foundations firmly rooted in the primate lineage."