GWD28-5

polaris16251

Social learning in animals
   is said to occur when direct
   or indirect social interaction
Line    facilitates the acquisition
(5)    of a novel behavior.  It
usually takes the form of
an experienced animal (the
demonstrator) performing a
behavior such that the naive
(10)    animal (the observer) sub-
sequently expresses the
same behavior sooner, or
more completely, than it
would have otherwise.  One
(15)    example of social learning
is the acquisition of prefer-
ences for novel foods.
     Some experiments
have suggested that among
(20)    mammals, social learning
   facilitates the identification
   of beneficial food items,
but that among birds, social
learning helps animals
(25)    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 subse-
   quently 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. 3 Studies
on nonavian species have
not produced similar results,
leading researchers to
(45)    speculate that avian social
learning may be fundamen-
tally different from that of
mammals.
     But Sherwin’s recent
(50)    experiments with domestic
hens do not support the
notion that avian social
learning necessarily facili-
tates aversion to novel
(55)    foods that are noxious or
toxic.  Even when demon-
strator 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
(65)    speculated that ecological
or social constraints during
the evolution of this species
might have resulted in there
being little benefit from the
(70)    social learning of unpal-
atability, for instance,
selective pressures for this
mode of learning would be
reduced if the birds rarely
(75)    encountered noxious or
toxic food or rarely inter-
acted 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
(90)    avian species can develop
preferences for palatable
food through social learning.

Q5:
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 Demonstrator hens reacted adversely to ingesting certain novel foods.
E Demonstrator hens altered their behavior less obviously in response to noxious foods than in response to highly palatable foods.


答案是E。

看过前人的讨论，E并不正确。但是我觉得B应该是正确的。正如标红的部分所述。难道是选项中only这个词太绝对了？

yorku

个人感觉应该选C
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.

C实际是对前半句的改写， disgust--adversely  certain food--specific food

victoria_cc

B貌似也不是很好，numerous不太对劲吧，文中说“ 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 ” ，并没有说明observer hens 要看很多次才会做出反应啊、