托福口语 Task 3

The concept of 'signaling theory' in biology suggests that certain physical traits or behaviors in animals have evolved primarily to convey information to other individuals, rather than for survival purposes alone. These signals are often honest indicators of the sender's quality or fitness, because they are costly to produce or maintain. For example, a peacock's elaborate tail is expensive to grow and makes the bird more vulnerable to predators, yet it accurately signals the male's health and genetic superiority to potential mates.

Professor: Let me give you a concrete example from a study on frogs. In certain species of male frogs, they produce a low-frequency croak to attract females. Now, you might think a louder or longer croak would be better, but actually, the depth of the croak is what matters. Researchers found that the size of the vocal sac and the body mass determine the pitch—larger frogs produce deeper sounds. And here's the key: producing a deep croak requires more lung capacity and muscle control, which is energetically costly. So only healthy, well-nourished males can maintain that deep call. Females, when given a choice, consistently prefer the deeper croaks, because those signals reliably indicate a male with better genes and stronger immune system. This is exactly like the peacock's tail—it's a costly signal that honestly advertises quality.