Hi shweta234

Remember that your job on inference/must be true questions is to pick the safest, most conservative answer you can find - even if it's boring and doesn't seem to say much. In fact, the more boring it is, the better answer it is for inference/must be true.



The passage uses the word "suggests" - note that this is not "proves" or "demonstrates" or "guarantees". But answer choice A says that the experiment provides "conclusive evidence." That is very strong language, and it should jump out to you when you read it. "Wow - conclusive evidence! Do they really have conclusive evidence? That would be pretty strong for a GMAT passage ... usually nothing gets proven 100% in an RC passage."

Meanwhile, E is extremely conservative and says something pretty obvious: if the researchers believed that the data from the experiment was strong enough to at least "suggest" that anteaters could be using a special sense to find unseen prey, well, the anteaters' results must have been better than random chance.

Does that help?

Best, Jennifer
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Hi Smiti
I understand you have asked for expert help and i am not one but just trying to help.

First lets get these facts straight
1) There is an animal by name Ant-eater (because it eats ants or whatever!)
2) It has two kinds of sensory's organs that can locate prey
3) the researches have identified them as electroreceptors and tactile receptors.
4) electroreceptors respond even to smallest of electrical fields where as tactile receptors respond to really strong electrical fields (like 1000 times greater that what electroreceptors respond to)

Now lets approach the questions

1. According to the passage, which of the following is a characteristic that distinguishes electroreceptors from tactile receptors?

(A) The manner in which electroreceptors respond to electrical stimuli its mentioned they respond to weak electrical signals but this dos not gives us the difference between the two receptors.
(B) The tendency of electroreceptors to be found in clustersthe passage merely mentions that electroreceptors but the passage does not say anything about how tactile receptors exist.So we cannot really comment on this and cannot identify any difference with 100% surity.
(C) The unusual locations in which electroreceptors are found in most species.The passage mentions that both the receptors are found on the anteater's snout. So this is infact a similarity between the two receptors.
(D) The amount of electrical stimulation required to excite electroreceptorsThe only difference between electroreceptors from tactile receptors that the author is pointing out is at the amount of electric simulation they respond to. In the passage the author mentions that while electroreceptors respond to "extremely weak electrical fields", the tactile receptors (also present on the anteater’s snout) responds to electrical field strengths about 1,000 times greater that those known to excite electroreceptors.
(E) The amount of nervous activity transmitted to the brain by electroreceptors when they are excitedThe passage just mentions that there is only recording of the transmission of nervous activity to the brain. No mention of the amount of nervous activity that is transmitted. Hence no basis for any comparison.

2. 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. The passage did not mention about any difficulties that the researchers might have faced in verifying the existence of the anteaters.
(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.No mention of this either. In the first paragraph the passage just says that the anteater's snout has some electroreceptors that respond to weak electrical fields and there are some tactile receptors on its snout that respond to extremely strong electrical fields.
(C) Researchers found that some areas of the anteater’s snout were not sensitive to a weak electrical stimulus.Yep! exactly how we summarized the first para in option B above.
(D) Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.The passage mentions that tactile receptors respond to strong electrical fields (about 1,000 times greater than those known to excite electroreceptors. However, the passage doesn't say that it responds easily or more easily. These tactile receptors just respond to strong electrical fields. Thats it!
(E) Researchers tested small areas of the anteater’s snout in order to ensure that only electroreceptors were responding to the stimulus.The passage says "The researchers made this discovery by exposing small areas of the snout to extremely weak electrical fields". Here the passage does not details out about how the researches have conducted the experiment.

3. The author of the passage most probably discusses the function of tactile receptors (lines 7-11) [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 electrical field strengths about 1,000 times greater than those known to excite electroreceptors.] in order to

(A) eliminate an alternative explanation of anteaters’ response to electrical stimuli.This is our answer. See if he had merely known that anteater has two kinds of sensory organs and both respond to electrical field then it could have been possible that when researchers were applying electrical fields to stimulate electroreceptors may be tactile receptors were responding. In that case the research would be rendered useless. By mentioning the fact that these tactile receptors need 1000 times greater electrical field than what electroreceptors need to respond the author has eliminated the possibility we mentioned above. This information about tactile receptors ensures us that it is indeed the electroreceptors that are responding and not the tactile ones.
(B) highlight a type of sensory organ that has a function identical to that of electroreceptorsThe passage does not mention any of the functions of tactile receptors. So this is irrelevant.
(C) point out a serious complication in the research on electroreceptors in anteaters.What sort of complication?? the passage doesn't mention any and if we are talking about response to electrical fields then that just cannot be a complication because electroreceptors respond to very weak electrical fields and tactile one's to very strong electrical fields and in order to identify electroreceptors the researchers exposed small areas of the snout to extremely weak electrical fields.
(D) suggest that tactile receptors assist electroreceptors in the detection of electrical signals.tactile receptors respond to electrical stimuli that is 1000 times greater than those known to excite electroreceptors. Cant see how tactile receptors can help electroreceptors.
(E) introduce a factor that was not addressed in the research on electroreceptors in anteaters.Cant see how this can be the answer. If the author is introducing any information it has a purpose.

I have explained only 3 answers. If you need help with other 3 also let me know. Happy to help

Q3: Last line of the passage clearly suggests that the researchers are agreeing that anteaters located the chambers quickly because of electroreceptors. Hence E

This ability quickly to locate unseen prey suggests, according to the researchers, that the anteaters were using their electroreceptors to locate the nesting chambers.

Q4. The hypotheseis that needs to be strengthened is "anteaters use electroreceptors to detect electrical signals given off by prey"

researchers experimented anteaters in a weak electrical field and concluded that anteaters can detect weak electrical signals and hypothesized their theory that anteaters use electroreceptors to locate their prey. But according to the passage, researchers are still not sure of any electrical signals emanating from termite mounds. This points out a gap in their hyposthesis. option B fillls the gap.

let me know if any further questions.

Ya... What you said about 3 is absolutely correct. Then how come the answer is E? It should be A. Your reasoning suggests A more than E. Am I missing something? 4 is fine.





C

Having discovered the electroreceptors, researchers are now investigating how anteaters utilize such a sophisticated sensory system. In one behavioral experiment, researchers 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, 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 to locate unseen prey suggests, according to the researchers, that the anteaters were using their electroreceptors to locate the nesting chambers.

I have divided the second para into three parts(using different colors)
Experiment in Red text already says that anteaters use electroreceptors to locate their prey. So if the question was about this experiment, option A would have been a better option. But the question talks about the experiment in blue text which only talks about how quickly anteaters were able to locate the prey colonies because of elecroreceptors.
Also, the last line of red text says anteaters use electroreceptors to detect electrical signals and the text in green says that researchers have been unable to detect any electrical signals emanating from prey colonies. This again holds against A which says conclusive evidence.

let me know if any further questions.

why C is the answer of question 102? isn't D a possible choice??

102. Which of the following can be inferred about the experiment described in the first paragraph?


(D) Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electro receptors..
==>here it is written that tactile receptors were more easily excited than electro receptors...
but there is no such comparison done that who will be more easily excited


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 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 respondto
electrical stimuli, such receptors do so only in
response to electrical field strengths about 1,000
times greater than those known to excite
electroreceptors.

hope it helps
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Im not quite sure to understand what do you mean

C say

(C) Researchers found that some areas of the anteater’s snout were not sensitive to a weak electrical stimulus.

Instead D say

(D) Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electro receptors..

Now, tp be honest D is the mostemtive answer choice among the others \(BUT\) D talks about electrical stimulus stronger instead the passage talks about



is not the same thing at all.........

For C we have

That's it. Hope is fine my explanation
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For question 5, I picked A, but the OA is E. Any explanation to this question?
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Just check the last two lines of the last para.

Still, researchers have observed anteaters
breaking into a nest of ants at an oblique angle and
quickly locating nesting chambers. This ability to
quickly locate unseen prey suggests, according to the
researchers, that the anteaters were using their
electroreceptors to locate the nesting chambers.

Even I chose A but then re read the last paragraph when I found my answer incorrect.

Hi sayantanc2k,
Can you please provide an explanantion for Q2?

My two cents:
Which of the following can be inferred about the experiment described in the first paragraph? [ 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 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 electrical field strengths about 1,000 times greater than those known to excite electroreceptors.

The likely options to get the reader confused :
(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.

Why is C the OA?
The finding of the little experiment is bold faced and is what we want to get our inference from. So from this sentence we know that electroreceptors are clustured at the tip of the snout, and hence, only this part responds to electrical fields. Which would mean some areas of the snout are not sensitive to a weal electrical stimulus.

Why is D not correct?
The ease with which or the affinity to strong electrical stimulus by tactile & electroreceptors has not been compared anywhere in the passage. Passage just talks about that tactile receptors getting excited to strong electrical stimulus. In fact, passage doesn't even mention, implicitly or explicitly, that electroreceptors get excited at all to strong electrical stimulus.

Hope this helps.
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Hi jennpt, can you please provide an explanation for

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.Clearly wrong
(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. Clearly wrong
(C) Researchers found that some areas of the anteater’s snout were not sensitive to a weak electrical stimulus.How can we infer this?
(D) Researchers found that the anteater’s tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.Clearly wrong. This was not what the experiment was about
(E) Researchers tested small areas of the anteater’s snout in order to ensure that only electroreceptors were responding to the stimulus.I picked this even though I did not fully support it but I could not find a better answer.

4. 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.

Here I was stuck between C and D. What through me off if the word "Consistently" in C. This was a one time experiment but the choice says consistently. D made more sense to me because the ant eaters reacted to the weak stimuli more than to no stimuli.

As always, thank you!
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Hi oasis90,

This is a fun one. I like picturing these crazy sophisticated anteaters and their supercool nose technology.

For Q2, I'll be honest, I initially picked E too. However, the truth is we really don't know how or if they made sure that only electroreceptors were responding. But we can prove C by putting two and two together (typical GMAT inference structure):
*We know that tactile receptors don't respond to weak electrical charges
*We know that tactile receptors are on the animal's snout
Therefore, we know that there are some areas on the animal's snout (namely the tactile receptors) that don't respond to weak electrical charges. This is the super-safe answer we can prove.

For Q4, I didn't like "consistently" in C very much either. But this was the key finding from the study - that the anteaters could be trained in this way - so I wouldn't characterize it as a one-off event. The researchers must have been able to replicate that happening a few different times in order to make that conclusion. If the results of the training had been inconsistent, the researchers could not have said they "successfully trained an anteater".

But D goes too far. What do we know about strong vs. weak stimuli? At least when it comes to electrical charges, we know that anteaters use different receptors to detect strong stimuli than they do to detect weak stimuli. Really, that's all we know. I don't have any evidence to make a comparison about how readily (easily/quickly) they detect strong vs. weak. In your note, you mentioned weak stimuli vs. no stimuli, which isn't the same as strong vs. weak.

Hope that helps; let me know.

Best, Jennifer
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Thanks Jennifer for the thorough explanation. This is kind of subtle. I thought about putting 2 and 2 together but maybe what threw me off is the word "Area". If the wording of the choice was "Some parts/receptors/mini-organs don't respond to weak stimuli" I would have selected it. When I saw area, I thought maybe tactile and electro receptors are both in the same vicinity so area is a generalization. Perhaps I am overthinking single words like I did with "consistently" below.

I think for Q4 I should have paid more attention to the word "readily" because, as you mentioned, there is no mention of that. and yes strong vs no is not the same as strong vs weak

Thanks again for your detailed explanation. I am reading many interesting and challenging OG passages and I will be reaching out with more questions.

Kind regards,

Oasis
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5. 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.

Hi Experts,
I was stuck between A and E while trying to figure out the answer. While E seems right A is too direct and directly picked up from the passage. Please explain why E is better over A.

Thanks

6. Which of the following, if true, would most strengthen the hypothesis mentioned in lines 17-19 [Such evidence is consistent with researchers’ hypothesis that anteaters use electroreceptors to detect electrical signals given off by prey]?

Here the passage is asking us to strengthen the hypothesis that anteaters actually use electroreceptors to detect electrical signals(weak signals) given off by its prey.So lets look for options that actually strengthens this fact.

(A) Researchers are able to train anteaters to break into an underground chamber that is emitting a strong electrical signal. Yes researchers can train the anteaters but here we need something to strengthen the fact that anteaters use electrical signals to detect their prey. This option doesn't give us that
(B) Researchers are able to detect a weak electrical signal emanating from the nesting chamber of an ant colony.Here the researchers detect that there are weak electrical signals coming out from the ant colony and as a result the anteaters can detect this signals and reach the prey. This is providing evidence to the fact that anteaters use electric signals to detect their prey and we can conclude this because now we know that these ants give out signals
(C) Anteaters are observed taking increasingly longer amounts of time to locate the nesting chambers of ants.The information about the time taken by the anteaters to locate the nesting chambers of ant is not relevant or useful in showing that these ant eaters use electrical signals to locate their prey.
(D) Anteaters are observed using various angles to break into nests of ants.Yet again the information about the angles anteaters use to break into nests of ants. gives no evidence or clue to conclude that they use electric signals to detect their prey.
(E) Anteaters are observed using the same angle used with nests of ants to break into the nests of other types of prey.Same as option D

I hope this helps

Passage map:
Overall the passage describes how a recent discovery concerning the Ant-eaters electroreceptors was made.
P1 – describes the experiment that led to the discovery and dispels the potential that the discovery is an alternate (tactile)
P2 – Applies the discovery to practical application – how the anteaters use it and some unexplainables.

Q1
A is incorrect as it is not the manner of response but the degree of stimulation required to get a response
B is incorrect because this cannot be supported
C is again not supportable
D is supported by the last sentence of the first para. , which states that although tactile sensors are triggered in the same way, the difference is that tactile requires 1000x greater electrical field strength
E ‘excited’ makes E incorrect

Q2
The first para. Describes an experiment in which two disparate electric stimulations were applied to small areas of the snout of the ant-eater – 1 low electrical field and 1 electrical field 1000x greater.

What can we infer?

A is incorrect for a number of reasons. Firstly, it seems researchers didn’t really have difficulty; second, the electroceptors were exposes to a large, not ‘narrow’, range.
B is false. We are told that “nervous activity TO THE BRAIN” not “IN THE BRAIN” increased.
C is correct because some receptors responded to weak electric fields, others responded to electric fields 1000x greater, so we can infer that “others” weren’t sensitive i.e. if they were sensitive then they wouldn’t require 1000x stimulation.
D is incorrect because logically the electroreceptors must be triggered first (before) the tactile receptors. E is false. We are told that electroceptors were discovered by exposure to weak electrical fields. The researchers didn’t explicitly test for the electroceptors. We are told that the reseachers “discovered” electroreceptors by “recording the transmission of resulting nervous activity “

Q3
Read the highlighted part and think about WHY this is in the passage.

Here, the author brings up tactile receptors, which are ALREADY KNOWN (as inferred since electro are only just discovered), to dispel/ refute the possibility that these may be the receptors causing the results that were seen.

Now imagine if the author hadn’t stated this in his passage and some random scientist came across and asked “what about tactile receptors? You forgot that these could be the cause”>?

A captures the above perfectly.
B is incorrect. The tactile may be similar but that’s not why the author brought this up.
C is incorrect – its not a complication, the author is merely dispelling
D is incorrect because the author points out two dissimilarities, not similarities
E is incorrect because the author does not bring this up to discuss something that wasn’t included in research. He dispels!

Q4
The experiment in question is a behavioural experiment in which researchers trained the ant-eater to differentiate between two troughs of water based on electric signals.
A is incorrect because the experiment only involved a ‘weak electric field’, and we know that tactile is triggered by 1000x greater fields
B is incorrect – we don’t know this. In fact later on we are told that electric signals aren’t given off.
C is correct – it can be 100% supported since the researchers trained the anteaters to detect a stimuls.
D is incorrect since we have no information on the ‘readiness’ by which the anteaters respond to stimuli
E is incorrect since we can’t support how anteaters interact between environments

Q5
The researchers in question observed anteaters break into nests that weren’t emitting signals, and eat their prey at oblique angles, quickly.

A is incorrect – the finding is generally weak. We are told that the reasearchers “as yet have been unable to detect” signals, so the observation isn’t exactly conclusive.
B – knowing what “atypical” means can help – it means “not representative”- if all this time we are told of evidence relating to one ant-eater then how can another observation relating to one ant-eater be non-representative?
C I incorrectly selected this. But I see that its incorrect as the observation was in fact used as evidence to support the claim the anteater uses their electroceptors for this hunting.
D is incorrect – probably the easiest to eliminate. We know the system isn’t exactly simple. If it were then the scientists would produce conclusive and strong conclusions.
E is correct because we are told that “researchers observed anteaters breaking into a nest….at an oblique angle and quickly locating nesting chambers”

This is analogous to someone walking into their bedroom at nighttime with the lights turned off and getting into bed. This person would rely on other sensors to navigate his way as well as his familiarity. What’s insinuated by E is that the fact the anteaters got into the nests awkwardly, but so quickly, makes it hard to believe that the anteater got lucky in identifying the ants.

Q6
The hypothesis is that anteaters detect prey via electroreceptors.
What have we got to believe this?
Pretty weak evidence – an observation (noted in Q5 above).

We need to strengthen this.
A – the ability to train the anteaters to detect STRONG signal does not serve as evidence to support the notion that anteaters rely on their electroreceptors, which detect WEAK SIGNALS.
B – This would 100% strengthen. It would explain why anteaters are so QUICK at locating prey.
C – This would weaken the hypothesis. How would this strengthen? It wouldn’t. It goes against the observation also.
D – It was moreso the QUICK ability of the anteaters to locate their prey. We need something that shows a reliance on electroreceptors and this answer choice just doesn’t do that.
E – the angle itself isn’t what led scientists to hypothesize that anteaters rely on their electroreceptors, again, it was the QUICK ability. This doesn’t strengthen.
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Hi AG95,

You messaged me to ask about how to eliminate answer choice B on question 3. I'm posting my response here in case it can help others as well.

Answer choice B can't work because it says "a function identical to that of electroreceptors." Identical is an extreme word, so you should always be suspicious of it in any RC answer choice. You would need really extreme language in the passage to justify that answer. However, the passage doesn't say that they have the exact same function - it says that they can have some of the same function (responding to electrical stimuli) but that the tactile receptors are not nearly as precise as the electroreceptors. So we can't justify an answer that says they have identical function.

Hope that helps - please let me know.

Best, Jennifer
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