TOEFL Listening: ETS-TOEFL听力机经 - 5468_L9X48846O5_

Lecture: Animal Communication: Narrator: Listen to part of a lecture in an animal behavior class. Professor: So we've been talking about animal communication. We know that often animals can signals of various kinds to attract the mate, to mark their territory, to set in another animal and so on. But there's an interesting aspect of animal communication that, well, before we get into that, let's take a human communication for a minute. Say, uh, let's say you don't feel too well, say you've got a headache and you see a friend on campus, and the friend says, "hey, how are you?". How you're gonna respond, probably, Kimi? Kimi: "Oh, I'm fine, thanks". Professor: Of course. Or you come to my office and say "Professor Anderson, I sound like a thousand sources for my paper". Professor: "A thousand, really?" I doubt it. What am I getting at here? Emma? Emma: They were exaggerated. They don't always tell the truth. Human communication is'nt always a 100% honest. Professor: Right! Often what humans say is governed by social expectations, a moral standard, but sometimes causes us to suspect the truth. But in nature, animal communication is a completely different situation. Let's see, uh, for example, when there are two animals, two lions of equal strength that both have their eye on the same piece of food they both wanted, but only one of them is gonna get it. What happens is rather than fighting, each lion signals it's true level of aggressiveness, how bad at once that food and how hard it is willing to fight for it. And the lion that's more aggressive, well, it wins, it gets the food and the less aggressive one doesn't. Kimi: But it's interesting that a little exaggeration could have helped the loser, right? I mean, it it pretended to be more aggressive than it really was. Then it would have gotten the food. Professor: It would have. But does this sort of thing sending thoughts or unreliable signals actually happened in the animal kingdom? Let's imagine the potential long term consequences of dishonesty and animals in terms of natural selection and evolution. Hypothetically speaking, suppose that some animals in the species, and say species of bears, deceived other bears by exaggerating the strength or aggressiveness. That means they'd win more resources like food, also more access to potential mate. So in this scenario, the individuals who signals are unreliable would reproduce more. So that tree of deception, dishonesty would be passed on to their offspring, and their offspring, and their offspring. Emma: So we'd have more and more individuals in that species that are, well, cheating, lying to them screwed on it. Kimi: So eventually they wouldn't know who to believe and who not to. They just stop listening to signals all together. Professor: Exactly. The individuals in the species would evolve to ignore communication signals. And eventually they evolved further not to bother producing signals at all. Communication would break down completely. Talk about chaos, so we conclude that dishonesty wouldn't benefit a species in the long run, because communication could eventually stop happening. But of course in the real world, communication hasn't stopped, the thing dogs bark, etc. So we can conclude that those signals, because they exist at all, must serve the purpose. They must be beneficial to the species in the long run. So they can't be dishonest. That is there must be signal reliability, honesty, in the animal kingdom. Emma: But I mean animals probably aren't thinking about long term benefit to the species. What's to stop individual animals from in graduating to help themself in the footrun, like, in that hypothetical scenario? Professor: Good question. There's an interesting but controversial hypothesis to consider, the handicap principle. The handicap principle says that signaling involves cost. Cost, meaning the energy an animal must extend to make a signal. So if a weaker animal increases the volume of duration of its localization to ward off a stronger rival, let's say, that weaker animal can use up a lot of energy that it needs for other activities, like finding food, and that could threaten its survival. So this could be a reason for signal reliability. An animal won't exaggerated strength or aggressiveness because it simply can't afford to. Instead, the stronger, healthier individuals will send better signals and therefore win more resources and reproduce more.