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From pointing to animated arm movements and nodding, people regularly use gestures to create and accompany language.
Now, it has been suggested that humans may also understand the sign language used by apes, meaning humans may have an ancestral understanding of ape communication.
According to one study, great apes use more than 80 signals to communicate their daily goals. study It was published Tuesday in the journal PLOS Biology.
These gestures include a “big, loud scratch”, which means “groom me” – monkeys do this to clean bugs or dirt from each other’s hair. It can mean “shaking an object”, “let’s have sex”, “fix me” or “walk away”. “directed thrust” means “climb on my back” for bonobos or “move to a new position” for chimpanzees.
chimpanzees Sharing more than 90% of their gestures, bonobos are humans’ closest living relatives, according to the study. Their gestures have been suggested to be an important framework in the evolution of human language, according to study authors Kirsty E. Graham, a research fellow at the University of St. Louis. Andrews’ School of Psychology and Neuroscience in Scotland and principal investigator in the university’s Wild Minds Laboratory, said primatologist Catherine Hobaiter.
The researchers found that infants aged 1 to 2 used more than 50 movements from the monkey repertoire. Therefore, it was thought that humans may have retained their understanding of the essential features of monkey movements.
The researchers used data from 5,656 participants who watched 20 online videos that were cropped to show a gesture made by a bonobo or chimpanzee, but did not have a triggered response. Participants were asked to choose the correct meaning of the gesture from among four possible options.
To include in the videos, the researchers selected the 10 most common types of gestures previously found to have meaning for both chimpanzees and bonobos. Each was accompanied by a simple demonstration of the gesture to help inexperienced viewers identify the action in the clips.
Each participant was randomly assigned a “video-only” game or videos with one line of context describing what the monkeys were doing before they moved.
This type of comprehension study was used to test non-human species’ understanding of human language, but this time the model was reversed.
Graham told CNN via email on Thursday that participants were able to successfully interpret chimpanzee and bonobo movements with just over 50% accuracy – twice as expected by chance. Up to 80% success was achieved with certain moves, such as “mouth slam” (which means “give me that food”) and “big, loud scratching”.
This ability was still present in determining the meaning of more ambiguous gestures with alternative meanings; “object waving” was the only gesture in which participants could assign neither primary nor alternative meanings.
“The fact that our participants were able to interpret primate signals complements recent findings that suggest humans can detect emotional cues in primate vocalizations,” the study authors wrote.
“These movements are shared by all other great ape species, and if humans understand them, then this looks like a wonderful ape movement ability that may have been used by our recent common ancestors,” Graham told CNN.
However, the researchers added that the underlying mechanism that allows humans to understand apes is still unsolved.
Some possible explanations for this conundrum include humans, apes, who have biologically inherited the great ape repertoire, and humans who share the general intelligence to interpret signals, common body plans, and social goals, or the similarity of gestures to the actions they aim to evoke.
“We need to examine how participants understand gestures – do people inherit a vocabulary or a capacity, or are we reasoning about it? That’s a big question that will require a variety of approaches to tackle,” Graham said.
“However, this experiment is an important proof of concept, and from there we can play with the information participants receive and ask participants more questions about how they interpret movements. We are also examining different communities of great apes in the wild to get a more complete picture of their movements.”
The researchers noted that gorilla and orangutan movements can also be interpreted by humans, but the meanings of the movements in these monkey species have not yet been determined.
“Dogs are also interesting because we’re not that closely related, but we’ve tamed and co-evolved with them over tens of thousands of years,” Graham added, “so how we communicate with them can also be very instructive for researchers.”
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