Q12 - The retina scanner

[catie0128]

I see how the answer is A, but why cant it be B?

[ManhattanPrepLSAT1]

The conclusion is that a retina scanner can be used to determine whether the scanner has ever scanned a retina of that person before. This means that it is within the retina scanner's capacity to determine whether it has scanned a retina of that person before - not that it will scan one retina and thereby determine whether it has ever scanned a retina of that person before, but whether it has ever scanned that retina before.

Also, this answer choice contradicts a premise of the argument that no two eyes have the same pattern of blood vessels in the retina. Answer choices that contradict a premise are not usually a good idea.

It needs to be true though for the conclusion to follow that the pattern of blood vessels in any retina does not potentially change between being scanned for the first time and then again for a second time. Otherwise the retina scanner will not correctly identify that it has scanned that eye before. This assumption is best expressed in answer choice (A).

(B) contradicts a premise.
(C) is irrelevant. The conclusion isn't that we'll be able store information on everyone's retinas. This answer choice would change the task of the conclusion.
(D) is irrelevant. The number of blood vessels in an eye, does not need to be the same for everyone.
(E) doesn't need to be assumed, because the conclusion is about whether one retina scanner would be able to detect an eye previously scanned by the same retina.

Hope that helps!

[austindyoung]

Matt's reason for eliminating AC (B) is solid. I struggled with this problem and got it correct. But I eliminated (B) for another reason.

I saw the conclusion as stating that (and this is different than Matt's reading) the retina scanner could determine if it had scanned a person's retina/s EVEN IF it had only scanned a retina from one eye.

That's because the conclusion says "whether it has EVER scanned A retina of that person before."

Now- here comes the problem. If the conclusion had said "both retinas" then (B) wouldn't be attractive. The problem that we LSATer's are asking is:

"Well, if a person only had one of their retinas scanned and inputed into the machine, and the other retina was scanned later, for the first time, then according to the argument given, it would determine that it had NOT "ever scanned a retina of that person before."

Now both (A) and (B) look attractive and we are seemingly in trouble.

Nope! Negation Test time. When we negate (B)
We see it doesn't destroy the argument. Why? Well, it seems that the LSAT had banked on you and I making our own unwarranted assumption doing this problem here.

Even if people don't have exactly the same pattern for each eye, the scanner could still be able to determine whether or not that person had their other retina scanned before. It doesn't matter how, but that it is not precluded from this stimulus shows that (B) does not need to be true.

I hope this helped for others who didn't catch Matt's way of reading the conclusion.

PS I wrote this on an iPhone and am too lazy to spell check.

[WaltGrace1983]

I get why (A) is right and all the others are wrong. However, for (A) to work, wouldn't we need to assume that there is at least one person who has an eye disease?

[ohthatpatrick]

Consider how (A) sounds when you negate it:

"diseases of the human eye DO alter the pattern of blood vessels ..."

Is there anything hypothetical about that?
No, it's a statement about what diseases of the human eye do out there in the real world.

Consider this sentence:
Watermelon is a delicious fruit.

Does that sentence 'assume' that at least one watermelon exists? No.

Assumptions only come from reasoning ... i.e. they only come from going from one idea to another.

We're not going to be taking individual sentences apart and saying that we are assuming that the 'noun' exists, or the 'verb'/'adjective' is possible.

A single idea is just a single idea. If it's presented as something hypothetical, then we don't have to believe that the sufficient idea exists. But statements presented as factual claims don't contain internal assumptions.

Hope this helps.

[lsatzen]

This might be redundant, but I had different reasons for eliminating (C) and (E). Hope a different perspective is useful to future LSAT students. MLSAT staff can feel free to ignore this post!

Premise:
(1) Retina scanner stores information about patterns formed by blood vessels
(2) This information allows it to recognize any pattern it has previously scanned
(3) No two eyes have identical patterns of blood vessels in retina

Conclusion:
(1) A retina scanner can be used successfully to determine for any person whether it has ever scanned a retina of that person before.

Real-time thought process:
Author is giving us neat fact about retina scanners. Could be background information or premises, unsure at this point. More features about the retina scanner, this doesn't seem like background information. Okay, previous sentence definitely was not useless background info, keep it in mind. Ah Ha! Author concludes that because of the two features of the retina scanner, it can determine its previous scanees. But wait, what if someone who has been scanned before gets in a gruesome accident and disfigures his / her eye beyond recognition? Move onto answer choices.

Answer Choices:
(A): Here we go, this perfectly addresses the issue that I thought of while reading the stimulus.
(B): Well this just plain contradicts the information given to us in the stimulus. Eliminate.
(C): This seems like a tempting answer choice, because what if there is too much information to be held in the entire system of retina scanner, what if we have to delete some previously stored data to make room for new data? But this concern is irrelevant because the conclusion is not concerned with the entire network of retina scanners, it is focused on a single / particular retina scanner. Further, the conclusion is about those who have been scanned, this answer choice includes those who potentially have not been scanned. Eliminate.
(D): Irrelevant. Concerned with patterns they form.
(E): Incorrect. This requires the additional and unwarranted inference that being cross-referenced within the supposed system of retina scanners causes some sort of interference with the readings.

[JennyF651]

The retain scanner is very awesome. I am using this with the help of my computer. Sometimes my windows laptop showing an error 0x80248007 otherwise It gives me the best scanning experience.

[Emmeline Ndongue]

Adding my thoughts on C

important premise: stored info allows the scanner to recognize any pattern it has previously scanned.
Con: the scanner can tell if it has scanned a single retina of a person before.

using the negation method, (C): IF there aren't enough scanners to store info of everybody, Con would fall.
suppose [1]all the scanners have used up its space, and [2]scanning a retina that hasn't been scanned before nor has its info stored for multiple times, you would get the [3]same result that it hasn't scanned it before, thus making the conclusion invalid.

but in order to do that, it has already take
[1] what if all the scanners combined aren't up to its capacity yet?
[2] what if it's not used to scanned sb who hasn't been scanned before?
[3] without storing info, the scanner can't recognize if a retina's pattern has previously been scanned
unwarranted assumptions for (C) to work.

so (B) is definitely a better answer choice