[讨论]gwd28-3-6

這是28篇

幫幫忙吧

我下星期就要考了

大家討論討論

28-passage one

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 naïve 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 (30) or a food in a distinctly

 marked container and then becoming ill, they subsequently avoided food 

associated with that color (35) or container. Another experiment showed that house sparrows consumed less red food after they observed others eating (40) red food that was treated so as to be noxious.  Studies on non-avian 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 (50) experiments with domestic hens do not support 

the notion that avian social learning necessarily facilitates aversion to novel 

(55) foods that are noxious or toxic. Even when demonstrator hens reacted

 with obvious disgust to a specific food, via vigorous head (60) 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 atability, 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. (80) 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.