Humans understand hand gestures of chimps and bonobos, says study
Humans are capable of recognizing and understanding hand gestures made by chimpanzees and bonobos, even though we stopped using them a long time ago, a reverse experiment carried out by researchers at St. Andrews University, Scotland, has found.
Video playback experiments are usually used by scientists to test language comprehension in non-human primates. These are a group of mammals that consist of simians which is a collective term for monkeys and apes, and prosimians, such as lemurs. Under research conditions, scientists use them to determine if the test subjects understand instructions given in human languages.
Researchers Kirsty E. Graham and Catherine Hobaiter at the Wild Minds Lab at the University of St.Andrews reverse the paradigm to determine whether humans could understand the gestures that our closest living relatives use during their communication. To make the study more interesting and get a large dataset to answer the question at hand, the researchers opened up the study to a large number of subjects by converting it into an online game.
How was the study conducted?
The researchers used the ten most common gestures used by chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) to make an online game. More than 5,600 participants were shown 20 short videos of ape gestures and asked to select the meaning of the gestures from four possible answers provided.
If the users were only guessing the answers, it would be expected that they would have a one in four chance of 25 percent likelihood of getting the answers right. However, the researchers found that most participants were able to interpret the meaning of the gestures more than 50 percent of the time.
The researchers even took the experiment a step ahead and provided participants with some context on what the apes were doing in the video. However, the improvement in getting the interpretation correct was only marginally better.
What does this mean?
Gestures used by apes are the first evidence of intentional communication recorded outside of human language. Over the years, researchers have identified more than 80 such gestures, and they have been found to exist even in distantly related apes such as chimpanzees and orangutans.
Although humans are more closely related to chimpanzees and bonobos, these gestures are no longer thought to be part of human communication. So, the finding that a sizeable number of people can correctly identify the gesture after so many years of evolutionary divergence can mean one of two things, researchers said in a press release.
Either human beings have retained an understanding of this ancestral communication system, or we, along with other great apes, share an ability to interpret meaningful signals by virtue of our general intelligence, physical resemblance, and similar social goals.
The research findings were published today in the journal PLOS Biology.
In the comparative study of human and nonhuman communication, ape gesturing provided the first demonstration of flexible, intentional communication outside human language. Rich repertoires of these gestures have been described in all ape species, bar one: us. Given that the majority of great ape gestural signals are shared, and their form appears biologically inherited, this creates a conundrum: Where did the ape gestures go in human communication? Here, we test human recognition and understanding of 10 of the most frequently used ape gestures. We crowdsourced data from 5,656 participants through an online game, which required them to select the meaning of chimpanzee and bonobo gestures in 20 videos. We show that humans may retain an understanding of ape gestural communication (either directly inherited or part of more general cognition), across gesture types and gesture meanings, with information on communicative context providing only a marginal improvement in success. By assessing comprehension, rather than production, we accessed part of the great ape gestural repertoire for the first time in adult humans. Cognitive access to an ancestral system of gesture appears to have been retained after our divergence from other apes, drawing deep evolutionary continuity between their communication and our own.
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