TOEFL Listening

🎧 Listening Transcript

Listen to part of a lecture in a biology class. The professor is discussing animal communication. Professor: Today we're going to look at how animals communicate, and specifically at a type of signal called a 'honest signal.' Now, in evolutionary biology, an honest signal is one that reliably indicates some quality of the animal, like its health or strength. For example, consider the peacock's tail. It's heavy, bright, and hard to grow, so only a truly healthy peacock can produce and carry such a tail. Thus, the tail is an honest signal of fitness. But why is it honest? Because it's costly to produce and maintain. If it were cheap, any weaker peacock could fake it, and the signal would lose its meaning. This costliness is what makes the signal reliable. However, not all signals are honest. Some animals use deceptive signals, like when a harmless snake mimics the warning colors of a venomous one. This is called a 'dishonest signal' because it falsely suggests danger. But dishonest signals only work if honest signals are common; otherwise, predators would learn to ignore the warning. So, in nature, there's a balance between honesty and deception, and that balance depends on the costs and benefits of each strategy.