但当黑猩猩在巩固与同类的社会联系时，也会微笑。
But chimpanzees also smile when they're trying to strengthen a social bond with another chimpanzee.
作者们写道，虽然在布林格的实验中黑猩猩清楚地明白如何合作，但它们更倾向于将自己的伙伴视为社会工具，能达到其目标的工具。
While the chimpanzees in Bullinger's experiment clearly understood how to collaborate, they likely viewed their partners as social tools, means to reach their own goals, the authors write.
它们生活在母系社会中，当然在倭黑猩猩的世界也有雄性，但负责做主的却是雌性，可想而知，它们的世界比黑猩猩平静多了。
It lives in a matriarchal society - there are blokes, but the birds are in charge - and it is more peaceful than the chimpanzee world.
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