托福口语 Task 4

Today we're going to talk about a fascinating concept in animal behavior called 'sensory bias.' This is when animals have an innate preference for certain physical traits or signals, not because those traits indicate good genes or health, but simply because they stimulate the animal's senses in a pleasing way. This preference can drive the evolution of exaggerated features in mates. Let me give you two examples. First, consider the guppy. Female guppies, in experiments, were shown to prefer males with more orange spots. Interestingly, this preference exists even in populations where males don't have orange spots at all—it's a pre-existing bias for orange, possibly because orange resembles their favorite food, fruit. Second, think of the swordtail fish. Females prefer males with a long sword-like extension on their tail fin. Even when researchers artificially attached a sword to males of a related species that naturally lack it, females still preferred the sworded males. So, in both cases, the preference is not about quality but about an ancestral sensory attraction.