Gorillas use a nonvocal form of "baby talk" to communicate with infants, a new study says. A first among primates, the discovery may give insight into how similar human communication evolved.
Lowland gorillas converse with each other primarily through nonvocal gestures.
Watch video of gorillas interacting with infants.
While researching how captive gorillas communicate during play, study leader Eva Maria Luef noticed that animals older than three years had a special way of interacting with younger gorillas. (See lowland gorilla pictures.)
With infants, the older gorillas used touch and repeated gestures—such as grabbing or stroking the infant's jaw—more frequently than they did when communicating with their peers.
"We were surprised that ... [gorilla] infants are addressed differently," said Luef, of the Department of Education and Psychology at Berlin's Freie University.
The behavior is evidence of a "gestural motherese," according to the study, published in June in the Journal of American Primatology.
Human motherese, or baby talk, is a universal mode of connection between adults and infants. Regardless of their language, people baby-talk in the same way, with a raised pitch and a swooping, sing-song style.
So far, the rhesus macaque is the only nonhuman primate known to use vocal baby talk.
(Also see "Monkeys Recognize Poor Grammar.")
Gorilla "Baby Talk" Observed
The team observed 24 gorillas, which they separated into four age groups: infants, juveniles, subadults, and adults.
The scientists focused on the animals' behavior during play bouts, which are started and ended via nonvocal communication-an exchange of signals involving the head, limbs, and body posture used to manipulate another gorilla's behavior.
Analyzing the video footage, the scientists then noted each gorilla's nonvocal signals.
The team saw that gorillas in the three older groups touched infants more, which may be because the youngsters themselves communicate with their mothers via touch, Luef said.
"The adults, when addressing them, may have that in mind, knowing the infants prefer tactile gestures," she said.
Luef is less certain about why the older gorillas repeated their gestures with infants, but it's possible that the older gorillas know that their messages are easier to comprehend when repeated, she said.
Gorilla Study Insight Into Human Evolution?
The research "provides some welcome [observation-based] evidence for what many primatologists probably already have observed and suspected," Steve Ross, director of the E. Fisher Center for the Study and Conservation of Apes, said by email.
Overall, "like many studies with primates, I think there is the potential to use this information to form some ideas about how human behavioral and cognitive processes have evolved," said Ross, who was not involved in the study.
For instance, primate infants learn mostly through passive observation, unlike human babies, who are actively taught many behaviors and concepts.
The repetitive motions and touches of the gorillas represents "an interesting middle ground that may help us understand when, in evolutionary time, other more-involved teaching abilities arose in our common ancestors," Ross said.
Study author Luef added that, in general, nonvocal language is too often neglected in primate-communication research. By contrast, human studies often incorporate both verbal and nonverbal language.
"That's the holistic approach to how we communicate—and we should do the same thing with apes."