Many people think that leaving a social situation without saying goodbye is rude—and it turns out that apes(类人猿) would agree.
As humans, we typically say we are leaving, shake hands or use other body language to signal when interactions with others are ending. Now Durham University researchers have discovered that apes such as bonobos and chimpanzees have a similar system, using gestures and physical contact to start and finish play or grooming sessions(梳毛时段).
The study observed 1,242 interactions within groups of bonobos and chimpanzees at zoos in the United States, Switzerland and France. In 90 percent of cases, bonobos used an "entry signal" before starting an interaction as well as a form of "exit signal" to end an interaction in 92 percent of cases. Chimpanzees used entry signals in 69 percent of cases and exit signals in 86 percent of cases. The closer the relationship between the animals, the shorter the gestures, researchers found. "When you're interacting with a good friend, you're less likely to put in a lot of effort in communicating politely," researcher Dr Raphaela Heesen said.
The ability to work for common causes was seen as a particularly human characteristic, made easier by our ability to communicate through language, butcollaborationcould also be seen in apes.
While the researchers were already aware that apes used signals to begin interactions, before the study they did not know if they did anything to mark ending and leaving them. Some earlier studies had compared apes with children who had not learnt to talk. When an adult played with a child and then suddenly stopped, the child would protest and want to keep playing. The apes did not appear to protest and so it was assumed that they did not require a signal to end an interaction. Dr Heesen said, however, that she had seen two bonobos interrupted while grooming each other. They then gestured to signal that they wanted to continue the grooming.
The study suggested the idea of "joint commitment" to shared attempts might have developed from our ape ancestors. The behavior among bonobos, in particular, has "some similarities to what, in humans, is considered 'social etiquette(社交礼仪)'."
