Q20 - Neural connections carrying signals

[ManhattanPrepLSAT1]

Question Type
Sufficient Assumption

Stimulus
The argument concludes that the influence the amygdala has on the cortex is greater than the influence the cortex has on the amygdala. The argument offers as support that the neural connections carrying signals between the two is stronger from the amygdala to the cortex rather than the other way around.

Answer Prephrase
The influence that a region of the body has on another is relative to the development of the neural connections carrying signals from that region to the other.

Correct Answer
(E) is correct. This answer links the amount of neural connections from one region of the body to another with the amount of influence that region has over the other.

Incorrect Answers
(A) is too weak. This fails to suggest which of the two regions exerts more influence over the other.

(B) is too weak. This establishes the amygdala as the region of the brain that exerts the most influence over the cortex, but fails doesn't indicate whether that influence is greater than the influence the cortex exerts on the amygdala.

(C) is too weak. While suggesting there is a link between neural connections and influence, this answer choice doesn't indicate whether the influence the amygdala exerts over the cortex is greater than the amount of influence the cortex exerts over the amygdala.

(D) is out of scope. Whether the amygdala is controlled by one or more other region of the brain doesn't eliminate the possibility that the amygdala could be influenced more by the cortex than vice versa.

#officialexplanation

[mdiaz.rod]

When I did this question I was between answer choices (D) and (E) and ended up choosing (D).

Looking at it now I see that (E) is the better answer because it links the development of neural connections to the influence and enables the conclusion to be drawn.

My reasoning with (D) was that if the amygdala is not controlled by some other part of the brain then the argument could never be weakened on the grounds that another part of the brain is actually exerting a greater influence on the cortex rather than the amygdala. It still seems like a pretty good answer. How do you avoid falling into traps like these?

[ohthatpatrick]

Hey, there.

Good question. Let me emphasize at the outset that my answer is SPECIFIC to Sufficient Assumption questions.

Sufficient Assumption is the most mathematical question type in Logical Reasoning.

To steal an analogy from Matt Sherman, this is essentially our task on Sufficient Assumption:
7 + 3 + _?_ = 15

Where '7' and '3' are the Premises, '?' is the Sufficient Assumption, and '15' is the Conclusion.

Our task in these problems is to logically (mathematically) prove the conclusion is true. We know the idea we're trying to prove. We know the premise ideas we have to work with. There is normally only 1 or 2 possible ways the correct answer could function. So we can fully predict the correct answer to these questions on 90% of them.

It's important that we know what an airtight argument really feels like: it's boring, mathematical, and mentions everything twice.

Here's an airtight argument:

Bob plays golf. No who plays golf is cool. Thus, Bob is not cool.

Notice that this properly drawn conclusion is a claim about "Bob" and about "whether or not he's cool".

Notice also that I have premises about "Bob" and about "whether or not someone is cool".

Everything is mentioned twice. That's the hallmark of an airtight argument.

If I say instead:
Bob plays golf. No who plays golf is cool. Thus, Bob is not invited to my party.


When we look at this conclusion, we should hear the record-scratch sound-effect and think, "not invited to my party??" Where did THAT idea come from?

I refer to a new term in a conclusion as The New Guy. The power of seeing The New Guy is that he MUST be in your correct answer.

Any crucial term in the conclusion that is ONLY mentioned in the conclusion MUST be in your correct answer (or some identical synonym to that term).

For this example, we would want a sufficient assumption that says "if you're not cool, you're not invited to my party".

Would we accept "if you're not invited to my party, you're not cool"? No. That's the most famous trap answer on Sufficient Assumption. That backwards logic won't allow us to prove the conclusion.

Would we accept "if you're not cool, you're not coming to my party."? No. "not coming" is not the same thing as "not invited".

Would we accept "if you're invited to my party, you're cool."? Yes. This is the contrapositive of the missing link we mentioned before. This is the most famous sneaky-correct answer on Sufficient Assumption.

So when I hit the conclusion on Q20 here, I see "the amygdala exerts a greater influence on the cortex than vice versa."

What's the New Guy? "Exerts a greater influence".

I don't see that term anywhere in the evidence, and yet it's the crux of what I'm trying to prove in my conclusion.

Hence, I can safely eliminate (D) since it doesn't mention that absolutely-critical wording of "exerts a greater influence".

The part of the conclusion that was NOT new was "the amygdala" and "the cortex".

What did we know from the premise about them?
Connections from A to C are better developed than from C to A.

What are we trying to prove?
A exerts a bigger influence on C than C exerts on A.

What is the missing link?
"better developed connections" --> "exert greater influence"

I've explained this all very structurally and robotically, because Sufficient Assumption is actually asking us to perform a very structural and robotic task.

But just to briefly address your argument for (D) conversationally, let's accept that the amygdala is not controlled by any other region of the brain.

That means that the cortex is the only region of the brain that exerts influence on the amygdala. We could thus say that the cortext exerts more influence on the amygdala than any other region of the brain exerts on the amygdala.

But would we still have any idea which is bigger: the amount the cortex influences the amygdala vs. the amount the amygdala influences the cortex?

No. (D) has nothing to do with judging Amygdala vs. Cortex. It only helps you judge Cortex vs. Other Regions of the Brain.

Hope this helps. Let me know if it elicits other questions.

[katherine.morales15]

I was between answer choices C and E for this question. I understood that a link between better developed connections and a greater influence needed to be made.

Answer choice C mentions both of these ideas. Is answer choice C wrong because it states that the cortex is the one that has the most highly developed neural connections when the argument only states that the connections between C and A are less developed than A and C?

Also, can you explain why answer choice E is correct?

[austindyoung]

I was between answer choices C and E for this question. I understood that a link between better developed connections and a greater influence needed to be made.

Answer choice C mentions both of these ideas. Is answer choice C wrong because it states that the cortex is the one that has the most highly developed neural connections when the argument only states that the connections between C and A are less developed than A and C?

Also, can you explain why answer choice E is correct?

So, we are looking for an answer that allows a causal connection to be drawn. ohthatpatrick did a fantastic job above explaining why (E) is correct here. The conclusion involves The New Guy, "greater influence" and that needs to be connected with development of neural connections.

The causality is really just a secondary issue in this problem; we're concerned about connecting the terms and filling the gap here. However, it is somewhat important for eliminating (C), which I'll get to.

So, (E) really does that perfectly. The only thing we know about the amygdala and the cortex are their neural connections relative to each other, and that the former has a greater development than the latter. From this, a conclusion is drawn about the amygdala having a greater influence. Well why? We need to connect the variables that we have, and greater development--->greater influence works perfectly-- which is what (E) says.

But why not (C)? It deals with the same variables, and isn't a mistaken reversal. You were on the right track- it is because "most" is present. But, that's not really the only reason it's wrong. In a Sufficient Assumption Question, we can actually have stronger-worded correct answer choices since we are looking for something that 100% guarantees the conclusion. But, "most," in answer choices still should be looked upon with a careful eye.

(C) is incorrect because it is out of scope for what we need. Put it into a conditional and it states, "If it has the most highly developed neural connections to the cortex, it has the most influence on the cortex."

There are a few problems with this.

First, (pardon the redundancy) what is it telling us? It's saying that if the part of the brain has the greatest neural connection to the cortex, then it is the most influential. That's all we get. Does it say that as neural connections increase that influence increases? No. We don't know if there's causality here, because we're dealing with a "most" statement. There's nowhere left to go, and we don't know if it has the greatest influence because of these connections.

Second, it actually could be because of something else entirely, and this part of the brain just happens to have the most highly developed neural connections. In other words, there could be no causal connection between the two, and it could even be a third factor that causes the influence, or the relationship could be reversed.

Finally, (E) works on the other hand because we actually have proportionality. The more you have of this thing, the more this second thing happens. Ahhh, causality. This involves degree, which the stimulus also deals with (it's not dealing with absolutes) and (E) is perfect.

[lsat2016]

Hello,

Could anyone explain answer choice B? I thought it bridged the gap because it both mentioned the word "influence" and "amygdala". Also, although it does seem extreme, I thought it was just going over filling the missing gap between the premise and the conclusion.

Thank you

[ohthatpatrick]

Sure thing. No worries about extreme on Sufficient Assumption.

ANY time a question stem is structured
"Which of the following, if true / if valid / if assumed .... "
there is no way to be too strong.

They are asking us, "IF you were to assume this, WOULD it prove the conclusion?"

Let's make this argument slightly easier to talk about by using a simple metaphor:

You've got a bunch of people in a room [parts of the brain] that all have some cash [influence]. They're going to give certain amounts of cash to people and receive certain amounts of cash from others.

And let's allude to the premise by saying that Andy is taller (more developed) than Charlie.

The conclusion wants to prove that Andy gave more money to Charlie than Charlie gave to Andy.

(B) says that Andy gave Charlie more money than anyone else gave to Charlie.

Okay, but we're not trying to compare how much money Andy gave Charlie vs. how much money everybody else gave Charlie.

We're trying to compare how much money Andy gave Charlie vs. how much money Charlie gave Andy.

I don't care if Andy gave Charlie $20 and everyone else gave Charlie less than $20. It could still be true that Charlie gave Andy $50, and that would invalidate the conclusion.

Continuing these answers in metaphorical form:
(A) the amount of money Andy gives other people depends (in what way?) on how much money Charlie gives other people.

[I don't care how much they give other people / just how much they give each other]

(B) just discussed above.

(C) "The person who gave Charlie the most money was the TALLEST person in the room". Cool ... but is Andy the tallest person in the room? I know he's TALLER than Charlie, but I don't know if he's the tallest. So this answer doesn't tell me anything about Andy, and therefore I can't use it to judge whether Andy gave Charlie more money or vice versa.

(D) "Other people in the room are not controlling how much cash Andy gives away". Okay. I don't really care whether they do or don't control Andy's cash. I just need to judge whether Andy gave Charlie more than Charlie gave Andy.

(E) "The amount of money you give someone is directly proportional to how tall you are" (i.e. the taller you are, the more money you'll give someone)

Sweet! I know Andy is taller than Charlie, so I know that Andy gave Charlie more money than Charlie gave Andy.


Hope this helps.

[JaylaJ306]

May someone confirm how E is the correct answer, considering that it does not contain the new "pop tart idea" from the conclusion. I have been following the suggested advice to eliminate answer choices that do not contain the new idea from the conclusion for all sufficient assumption questions. As a result, I skimmed E and eliminated it quickly because it did not mention the word "cortex". Please help.

[Annie Levin]

To the question about pop tart idea, in this case "cortex" isn't the pop tart idea in the conclusion; the cortex is mentioned multiple times in the premise, so it's not new when we see it in the conclusion. The new concept that pops up in the conclusion in this case is "greater influence"--that's what we need to address. Answer choice E address "influence," our pop tart idea in this case.