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.
28-5: According to the passage, which of the following is true of the experiments on domestic hens conducted by Sherwin’s research team?
A: Only a small number of observer hens appeared to learn to avoid food that was demonstrated by other hens to be noxious.
B: Observer hens ingested food preferentially only after numerous instances of witnessing demonstrator hens preferentially ingest that type of food.
C: Observer hens appeared unable to recognize when demonstrator hens found a particular food especially palatable.
D: Observer hens appeared unable to recognize when demonstrator hens found a particular food especially palatable.
E: Demonstrator hens altered their behavior less obviously in response to noxious foods than in response to highly palatable foods.
看上面的讨论,大家都觉得选E,可是我不明白怎么从文中得出E是正确的呢,多谢NN指点!
另外这个题C,D答案给的是一样的,是不是其中有可能有个是正确。
[此贴子已经被作者于2005-8-5 11:05:10编辑过] |