#17 - Science writer: The deterioration of cognitive

[ericau02]

I am a little confused on how one would be able to catch that connection or linkage btween the two. I have re read it over a couple times but still are not able to see the connection.

[Adam Tyson]

The author is arguing that microglia (immune cells) cause cognitive deterioration, and provides two bits of evidence. One is that microglia attack the BA deposits and, in the process, destroy healthy surrounding cells, which causes that deterioration. That causal chain is complete - we have been given all we need to see one way that microglia are to blame.

Then there's the second bit of evidence: acetylsalicylic acid slows the deterioration. What does that have to do with microglia? The stimulus neglects to tell us, so we should be asking ourselves what that has to do with the conclusion. There's a gap there.

When we are asked to strengthen the argument, look for a weakness that needs fixing, a gap that needs to be filled. The bit about BA deposits is already solid and needs no help, so we should be looking to that other premise about acetylsalicylic acid to try and connect that to the conclusion. That's how we know to link those two things, Erica! Because that is the only weakness in the argument that we are trying to strengthen! If we know that the acid is somehow related to the microglia, reducing it or blocking it in some way, that gap will close, and the argument will be better.

In this way, this works a lot like the mechanistic approach to a Justify the Conclusion question, where we seek to connect the rogue elements. We should always be looking for those gaps and considering how to fix them, or to take advantage of them, or to describe them, depending on what type of question we are asked.

[ericau02]

Great thanks Adam!!!

[Oneblackcoffee]

Complete Question Explanation

Strengthen—CE. The correct answer choice is (B)

This stimulus can appear intimidating for students who may not be comfortable with science terminology. However, just as in reading comprehension, our focus is not on the exact scientific process described. We do not need any independent knowledge of Alzheimer’s or brain physiology in order to answer the question. We just need to focus on the internal logic of the argument as we would in any other stimulus.

The stimulus begins with the conclusion: The deterioration of cognitive functioning in Alzheimer’s patients is caused by the activities of microglia. The causal reasoning can be diagramed as follows:

• Activities of microglia (cause) Cognitive decline (effect)

The scientist supports the causal relationship by observing that Alzheimer’s patients are unable to eliminate a certain protein from their brain, where it builds up. Apparently, the microglia attack both the harmful deposits, as well as healthy brain cells, which causes the cognitive decline.

It isn't immediately apparent how the premise about acetylsalicylic acid (aka Aspirin) supports the conclusion that the activities of microglia are involved in the cognitive decline of patients suffering from Alzheimer's, which is precisely why answer choice (B) works so well: it connects that premise to the conclusion of the argument!

Answer choice (A): I understand why this seems like an attractive answer choice: it shows that the immune system is the very reason why patients cannot eliminate the protein BA from their brain, where it builds up and causes the microglia to attack the deposits. It's a vicious circle, if you will. However, this does not support the observation that the microglia specifically are responsible for the decline! Remember - the microglia are the brain's immune cells, not the brain's "immune system." We can blame the immune system for the buildup of deposits, but that doesn't establish that the microglia are responsible for attacking those deposits, thus causing cognitive decline.

Answer choice (B): This is the correct answer choice. As mentioned earlier, the statement that certain anti-inflammatory drugs can slow cognitive deterioration had no direct relevance to the conclusion. If answer choice (B) is true, however, it does! If anti-inflammatory drugs both decrease the production of microglia, as stated here, and also help ameliorate the cognitive decline, as stated in the premise, it becomes even more likely that the microglia is involved in this cognitive decline. Answer choice (B) establishes correlates the decrease of microglia with the slowing of cognitive decline, which naturally supports a causal relationship between the two.

Answer choice (C): The stimulus already states that the microglia attack the protein deposits, and thus, we would expect them to also decrease the buildup of protein deposits in the brain. This does not provide additional information to support the argument and is therefore irrelevant.

Answer choice (D): This answer choice actually weakens the argument, because it suggests an alternative cause for the cognitive decline - it's not microglia, it's the protein itself, that causes the decline.

Answer choice (E): Even if microglia are active in patients whose brains have other diseases, we have no reason to suspect that the effects of this activity involve any cognitive decline.

Hi,

I understand why (B) is correct, but I was hoping to dive a bit deeper into (C). While the stimulus does say that the microglia attack the protein deposits, it doesn’t say that the microglia are successful in decreasing these deposits. Thus, by saying that the microglia are actually successful in decreasing the protein deposits (answer (C)), we can rule out that the protein deposits are an alternative cause of the deterioration of cognitive faculties.

Thanks for your help in advance.

[Paul Marsh]

Hi Oneblackcoffee! You're right that ruling out alternate causes can often be a good answer for a Strengthen question in which the argument in the stimulus uses cause and effect reasoning. And you make a good point about how answer choice (C) sort of weakens a possible alternate cause of excess protein buildup. However, (C) is still wrong for a couple reasons.

First, the additional fact that microglia decrease protein deposits doesn't really eliminate the possibility that protein deposits are an alternate cause of cognitive function deterioration. Just because the protein deposits decrease doesn't mean that they're wiped out, or even reduced by a significant amount. It could be that any excess protein build-up still causes cognitive function deterioration. So the alternate cause isn't eliminated, making (C) a poor strengthener.

Second, while there is a gap between the microglia "attacking" protein deposits and the microglia "decreasing" protein deposits, it's a fairly small one. In other words, it's an assumption but it's not much of an assumption. If I say, "Man I really attacked those cupcakes in the breakroom yesterday," it's probably safe to say I decreased their number a bit.

For both of those reasons,(C) is overall a poor strengthener. The question stem asks us which answer choice "most helps", and Answer Choice (B) (for all the reasons explained very well by other instructors above) clearly does more to strengthen gaps in the argument.

As a final note, this is another good example of why pre-phrasing (coming up with a good answer before looking at the answer choices) is so important. When pre-phrasing a Strengthen question, the most important thing is to look at gaps in reasoning between the premises and the conclusions. Here there is a clear gap between the premise regarding acetylsalicylic acid and the conclusion, so identifying that allows you to be on the lookout for any answer choice dealing with acetylsalicylic acid. Hope that helps!