Аудирование TOEFL

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Listen to part of a lecture in a biology class. The professor is discussing animal communication. Professor: Today we're going to talk about how animals communicate, and I want to focus on a concept called the 'referential signal.' A referential signal is a specific call or display that refers to a particular object or event in the environment. For example, vervet monkeys have distinct alarm calls for different predators—like eagles, snakes, and leopards. Each call triggers a different escape response: if they hear the eagle call, they look up; if they hear the snake call, they stand up and look around on the ground. This suggests the calls are not just expressions of fear but are referential—they convey specific information about the type of threat. However, some researchers argue that these calls might simply be variations in intensity of fear, not true references. To test this, scientists played back recorded alarm calls to monkeys in the absence of any predator. The monkeys responded appropriately to each call type, which supports the idea that the calls are referential. This research is important because it challenges the traditional view that animal communication is purely emotional and not symbolic.