Humans can recognize and understand chimpanzees

Humans retain an understanding of other great apes’ gestures even though we no longer use them ourselves, according to a study by Kirsty E. Graham and Catherine Hobaiter of the University of St Andrews, Scotland, published January 24^th in the open access journal PLOS biology.

The discovery of gestures used by great apes provided the first evidence of intentional communication outside of human language, and over 80 such signals have now been identified. Many of these gestures are shared by non-human apes, including distantly related apes such as chimpanzees and orangutans. Although humans are more closely related to chimpanzees and bonobos, these simian gestures are believed to be absent in human communication.

The researchers tested people’s understanding of the 10 most common gestures made by chimpanzees (Pan Caveman) and bonobos (Pan panic) with an online game. Over 5,500 participants were asked to watch 20 short videos of monkey gestures and choose the meaning of the gesture from four possible answers. They found that the participants performed significantly better than randomly expected, correctly interpreting the meaning of the chimpanzee and bonobo gestures over 50% of the time. Giving participants contextual information about what the monkeys were doing in the video only slightly increased their success rate in interpreting the meaning of the gesture.

Video playback experiments have traditionally been used to test language comprehension in nonhuman primates, but this study reversed the paradigm to assess, for the first time, humans’ ability to understand the gestures of their closest living relatives. The results suggest that although we no longer use these gestures, we may have retained an understanding of this ancestral communication system. The authors say it remains unclear whether our ability to understand certain great apes gestures is inherited, or whether humans and other great apes share the ability to interpret meaningful signals because of their overall intelligence, physical similarity, and similar social goals.

The authors also add a link for people to take a quiz version of the experiment (no data is collected): https://research.sc/participant/login/dynamic/505CF355-CEF5-44ED-B2F1-2CBA484BD2FA

Graham adds, “All great apes use gestures, but humans are so gesturing—they use gestures as we speak and sign, learn new gestures, pantomime, etc.—that it’s really difficult to spot common apes gestures by looking at them.” just watching people. By instead showing participants videos of common ape gestures, we found that humans can understand these gestures, suggesting they may be part of an evolutionarily ancient, common gestural vocabulary of all great ape species, including us.”

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Please use this URL in your reporting to enable access to the freely available paper PLOS biology: http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3001939

Citation: Graham KE, Hobaiter C (2023) Towards a dictionary of the great apes: Inexperienced humans understand common nonhuman ape gestures. PLoS Biol 21(1): e3001939. https://doi.org/10.1371/journal.pbio.3001939

author countries: United Kingdom

Financing: This research was funded by the European Union’s 8th Framework Program 287, Horizon 2020, under grant agreement No. 802719 to CH (https://ec.europa.eu/info/research-and-innovation/funding/funding-opportunities/ funding- programs -and-open-calls/horizon-2020_en). This work was supported by the Gorilla Awards in Behavioral Science, which provided the Gorilla.sc license fee and an unlimited participant award to KG (https://gorilla.sc/). The funders played no role in the study design, data collection and analysis, the decision to publish, or the preparation of the manuscript.