Reading Comprehension

Australian researchers have discovered electroreceptors

(sensory organs designed to respond to electrical fields)

clustered at the tip of the spiny anteater's snout. The

researchers made this discovery by exposing small areas of

(5) the snout to extremely weak electrical fields and recording

the transmission of resulting nervous activity to the brain.

While it is true that tactile receptors, another kind of

sensory organ on the anteater's snout, can also respond to

electrical stimuli, such receptors do so only in response to

( 10) electrical field strengths about 1,000 times greater than

those known to excite electroreceptors.

Having discovered the electroreceptors, researchers are

now investigating how anteaters utilize such a sophisticated

sensory system. In one behavioral experiment, researchers

(15) successfully trained an anteater to distinguish between

two troughs of water, one with a weak electrical field

and the other with none. Such evidence is consistent with

researchers' hypothesis that anteaters use electroreceptors

to detect electrical signals given off by prey; however,

( 20) researchers as yet have been unable to detect electrical

signals emanating from termite mounds, where the favorite

food of anteaters live. Still, researchers have observed

anteaters breaking into a nest of ants at an oblique angle

and quickly locating nesting chambers. This ability quickly

(25)to locate unseen prey suggests, according to the researchers, that the anteaters were using their electroreceptors

to locate the nesting chambers.

) Which of the following can be inferred about the experiment described in the first paragraph?
(A) Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths.
(B) Researchers found that the level of nervous activity in the anteater?s brain increased dramatically as the strength of the electrical stimulus was increased.
(C) Researchers found that some areas of the anteater?s snout were not sensitive to a weak electrical stimulus.
(D) Researchers found that the anteater?s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.
(E) Researchers tested small areas of the anteater?s snout in order to ensure that only electroreceptors were responding to the stimulus.

OA - C

Kindly explain reason and especially why it cannot be D

saxenashobhit wrote:Australian researchers have discovered electroreceptors

(sensory organs designed to respond to electrical fields)

clustered at the tip of the spiny anteater's snout. The

researchers made this discovery by exposing small areas of

(5) the snout to extremely weak electrical fields and recording

the transmission of resulting nervous activity to the brain.

While it is true that tactile receptors, another kind of

sensory organ on the anteater's snout, can also respond to

electrical stimuli, such receptors do so only in response to

( 10) electrical field strengths about 1,000 times greater than

those known to excite electroreceptors.

Having discovered the electroreceptors, researchers are

now investigating how anteaters utilize such a sophisticated

sensory system. In one behavioral experiment, researchers

(15) successfully trained an anteater to distinguish between

two troughs of water, one with a weak electrical field

and the other with none. Such evidence is consistent with

researchers' hypothesis that anteaters use electroreceptors

to detect electrical signals given off by prey; however,

( 20) researchers as yet have been unable to detect electrical

signals emanating from termite mounds, where the favorite

food of anteaters live. Still, researchers have observed

anteaters breaking into a nest of ants at an oblique angle

and quickly locating nesting chambers. This ability quickly

(25)to locate unseen prey suggests, according to the researchers, that the anteaters were using their electroreceptors

to locate the nesting chambers.

) Which of the following can be inferred about the experiment described in the first paragraph?
(A) Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths.
(B) Researchers found that the level of nervous activity in the anteater?s brain increased dramatically as the strength of the electrical stimulus was increased.
(C) Researchers found that some areas of the anteater?s snout were not sensitive to a weak electrical stimulus.
(D) Researchers found that the anteater?s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.
(E) Researchers tested small areas of the anteater?s snout in order to ensure that only electroreceptors were responding to the stimulus.

OA - C

Kindly explain reason and especially why it cannot be D

the first sentence says that the receptors are clustered at the tip of the snout - implying that there are no receptors in other parts of the snout, which means that there are other areas of the snout (not the tip) that will not respond to electrical stimulus.

D actually says the opposite of what the passage does. According to the passage, the tactile receptors only respond to such receptors do so only in response to ( 10) electrical field strengths about 1,000 times greater than that excite electroreceptors. Tactile is less sensitive - it requires a stronger pulse to respond.

Hi Geva,

Option D says "tactile receptors were more easily excited by a strong electrical stimulus". In other words tactile receptors respond easily to stronger signals(electrical field strengths about 1,000 times greater than). Tactile receptors seem to be sensitive to strong electrical stimulus. So isn't this inference correct which can be verified by facts given in para?

saxenashobhit wrote:Hi Geva,

Option D says "tactile receptors were more easily excited by a strong electrical stimulus". In other words tactile receptors respond easily to stronger signals(electrical field strengths about 1,000 times greater than). Tactile receptors seem to be sensitive to strong electrical stimulus. So isn't this inference correct which can be verified by facts given in para?

Ok, let's really take D apart: Researchers found that the anteater?s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.

so the compariso is that tactile is more easily excited...than electroreceptors (to strong electrical stimulus).
The problem is that you do not even know how the electroreceptors respond to strong stimulus - the experiment only subjected them to weak stimulus. So we can't really infer for strong.

but even if we could infer, D actually goes in the opposite direction: if the electrorecetors are more sensitive than tactile receptors (because electro responds to weak stimulus, while tactile needs a 10,000 stronger electro-hammer to the head to even notice) then logically electro will be even MORE sensitive to strong stimuli than their tactile counterparts: Think of your girlfriend, who wakes up at your every move, while you sleep like a log through anything. If a bomb drops outside while you both sleep, who will wake up first?

Thanks Geva, Now I understand what mistake I was making. I had assumed that electro-receptors ONLY respond to weak signals. So I was thinking that they will not respond when 1000 times strong signal is given. In-correct assumption on my part which made me select wrong choice.

Thanks for explaining - girlfriend example brought me to reality

saxenashobhit wrote:Thanks Geva, Now I understand what mistake I was making. I had assumed that electro-receptors ONLY respond to weak signals. So I was thinking that they will not respond when 1000 times strong signal is given. In-correct assumption on my part which made me select wrong choice.

Thanks for explaining - girlfriend example brought me to reality

You're welcome. I was assuming that you're a male hobhit.

Which of the following can be inferred about anteaters from the behavioral experiment mentioned in the second paragraph?

(A) They are unable to distinguish between stimuli detected by their electroreceptors and stimuli detected by their tactile receptors.
(B) They are unable to distinguish between the electrical signals emanating from termite mounds and those emanating from ant nests.
(C) They can be trained to recognize consistently the presence of a particular stimulus.
(D) They react more readily to strong than to weak stimuli.
(E) They are more efficient at detecting stimuli in a controlled environment than in a natural environment.

11. The passage suggests that the researchers mentioned in the second paragraph who observed anteaters break into a nest of ants would most likely agree with which of the following statements?

(A) The event they observed provides conclusive evidence that anteaters use their electroreceptors to locate unseen prey.
(B) The event they observed was atypical and may not reflect the usual hunting practices of anteaters.
(C) It is likely that the anteaters located the ants' nesting chambers without the assistance of electroreceptors.
(D) Anteaters possess a very simple sensory system for use in locating prey.
(E) The speed with which the anteaters located their prey is greater than what might be expected on the basis of chance alone.

Which of the following, if true, would most strengthen the hypothesis mentioned in lines 17-19?

(A) Researchers are able to train anteaters to break into an underground chamber that is emitting a strong electrical signal.
(B) Researchers are able to detect a weak electrical signal emanating from the nesting chamber of an ant colony.
(C) Anteaters are observed taking increasingly longer amounts of time to locate the nesting chambers of ants.
(D) Anteaters are observed using various angles to break into nests of ants.
(E) Anteaters are observed using the same angle used with nests of ants to break into the nests of other types of prey.

I answered these questions wrongly.I marked them as BAA but the correct answers are CEB. Can any1 explain?

Thanks,
Shreeraj