Social learning in animals is said to occur when direct or indirect social interaction facilitates the acquisition of a novel behavior. It usually takes the form of an experienced animal (the demonstrator) performing a behavior such that the naive animal (the observer) subsequently expresses the same behavior sooner, or more completely, than it would have otherwise. One example of social learning is the acquisition of preferences for novel foods.

Some experiments have suggested that among mammals, social learning facilitates the identification of beneficial food items, but that among birds, social learning helps animals avoid toxic substances. For example, one study showed that when red-wing blackbirds observed others consuming a colored food or a food in a distinctly marked container and then becoming ill, they subsequently avoided food associated with that color or container. Another experiment showed that house sparrows consumed less red food after they observed others eating red food that was treated so as to be noxious. Studies on nonavian species have not produced similar results, leading researchers to speculate that avian social learning may be fundamentally different from that of mammals.

But Sherwin's recent experiments with domestic hens do not support the notion that avian social learning necessarily facilitates aversion to novel foods that are noxious or toxic. Even when demonstrator hens reacted with obvious disgust to a specific food, via vigorous head shaking and bill wiping, there was no evidence that observers subsequently avoided eating that food. Sherwin's research team speculated that ecological or social constraints during the evolution of this species might have resulted in there being little benefit from the social learning of unpalatability, for instance, selective pressures for this mode of learning would be reduced if the birds rarely encountered noxious or toxic food or rarely interacted after eating such food, or if the consequences of ingestion were minimal. In a related experiment, the same researchers showed that if observer hens watched demonstrator hens react favorably to food of a particular color, then observer hens ate more food of that color than they ate of food of other colors. These results confirmed that avian species can develop preferences for palatable food through social learning.


The primary purpose of the passage is to discuss the


techniques used in certain experiments on social learning in birds

reasons for the differences between social learning in birds and in mammals

question of how social learning manifests itself in birds

basis for a widespread belief about a difference in behavior between birds and mammals

possible reasons why birds may or may not learn from each other in a particular way

考题讲解

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正确答案: E. 可能的原因为什么鸟可能或不可能以特定方式学习彼此。

该文章主要讨论的是动物社会学习在鸟类和哺乳动物之间的差异。文章开始提出了动物社会学习的定义,并介绍了它如何在哺乳动物中表现出来。文章接着讨论了实验的结果,其中有些实验表明,在哺乳动物中,社会学习有助于识别有益的食物,而在鸟类中,社会学习有助于避免有毒物质。然后,文章讨论了 Sherwin 最近的实验并得出结论,尽管家禽表现出对特定食物的厌恶情绪,观察者鸟仍然不避免食用这种食物,可能是因为在这种物种进化过程中存在一些生态或社会约束。最后,文章讨论了家禽可以通过社会学习发展出对可口食物的偏好。由此可见,本文的主要目的是讨论鸟类和哺乳动物之间在社会学习方面可能存在的差异,以及可能的原因,因此,正确答案是 E 选项:可能的原因为什么鸟可能或不可能以特定方式学习彼此。

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