GWD28-Q3

GWD28-Q3to Q6:
   Social learning in animals is said tooccur when direct or indirect social interaction facilitates the acquisition ofa novel behavior.  It usually takes theform of an experienced animal (the demonstrator) performing a behavior suchthat the naïve animal (the observer) subsequently expresses the same behaviorsooner, or more completely, than it would have otherwise.  One example of social learning is theacquisition of preferences for novel foods.
   Some experiments have suggested thatamong mammals, social learning facilitates the identification of beneficialfood items, but that among birds, social learning helps animals avoid toxicsubstances. For example, one study showed that when red-wing blackbirdsobserved others consuming a colored food or a food in a distinctly markedcontainer and then becoming ill, they subsequently avoided food associated withthat color or container.  Another experimentshowed that house sparrows consumed less red food after they observed otherseating red food that was treated so as to be noxious.  Studies on nonavian species have not producedsimilar results, leading researchers to speculate that avian social learningmay be fundamentally different from that of mammals.
   ButSherwin’s recent experiments with domestic hens do not support the notion thatavian social learning necessarily facilitates aversion to novel foods that arenoxious or toxic.  Even when demonstratorhens reacted with obvious disgust to a specific food, via vigorous head shakingand bill wiping, there was no evidence that observers subsequently avoidedeating that food. Sherwin’s research team speculated that ecological or socialconstraints during the evolution of this species might have resulted in there beinglittle benefit from the social learning of unpalatability, for instance, selectivepressures for this mode of learning would be reduced if the birds rarely encounterednoxious or toxic food or rarely interacted after eating such food, or if theconsequences of ingestion were minimal. In a related experiment, the sameresearchers showed that if observer hens watched demonstrator hens reactfavorably to food of a particular color, then observer hens ate more food ofthat color than they ate of food of other colors. These results confirmed that avianspecies can develop preferences for palatable food through social learning.
Q3:
Theprimary purpose of the passage is to discuss the
A.techniques used in certain experiments onsocial learning in birds
B.reasons for the differences between sociallearning in birds and in mammals
C.question of how social learningmanifests itself in birds
D.basis for a widespread belief about adifference in behavior between birds and mammals
E.possible reasons why birds may or may notlearn from each other in a particular way

为什么不是E呢...我觉得文章确实是在解释为什么跟着吃为什么不跟着吃。。