Apes don't have a spoken language, but researchers at St Andrews University have discovered that people can often understand the precise meaning of the signals they use. Peter Smith reports
Humans are able to better understand other great apes than first thought possible, according to a new study.
Research has shown that gestures made by bonobos and chimpanzees can have their meaning determined by adult humans, even though we do not use such gestures ourselves.
The study, which was conducted by Dr Kirsty Graham and Dr Catherine Hobaiter, has now provided fresh evidence to highlight the strength of understanding between humans and some of our closest living ancestors.
They looked at data which was sourced from 5,656 volunteers, taking part in an online game where they were asked to select the meaning of bonobo and chimpanzee gestures in 20 videos.
Included within these were signals to "groom me", "give me that food" and "let's have sex".
The participants were also provided each time with an illustration of the gesture, some of which had more than one meaning. Identifying the correct definition depended on the context of the gesture.
At random, each participant was allocated either to watch the gestures with text on what the apes were up to before the gesture or without this information. They were then asked to select the correct meaning from four possible answers.
When the results were analysed it revealed that the participants were better than chance at correctly identifying the meanings of the gestures, regardless of whether any context was provided.
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Those who were given contextual information made an average success rate of 57% and those who were given nothing scored 52%.
Writing in the PLOS Biology journal, the researchers said: "Participants were highly successful at detecting the meaning for which gestures were used in the specific instance of communication that they saw.
"Where gestures had alternate meanings, these were also detected more often than chance in two gesture types.
"That our participants were able to interpret primate signals complements recent findings that suggest humans may be able to perceive affective cues in primate vocalisations."
Dr Graham and Dr Hobaiter said it was unclear how humans and other great apes are able to understand such gestures, arguing that it could be due to a combination of "cognitive mechanisms" in humans and biological inheritance in non-human apes.
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