#10 - A recent study suggests that Alzheimer’s disease,

[Johnclem]

Hello,
For this lovely question i just want to know if my reson for eliminating E is right. I saw E as also strengthening the argument . As it states where the casuse doesn't occur the effect doesn't occur. However I ended up eliminating it because I felt it only strengthened the premise , but it left us hanging with whether or not Jacob and alzimer are related . Since if they were not we wouldn't be able to say the virus causes alzimers.


Thanks
John

[Claire Horan]

Hi John,

I agree with you that choice (E) does strengthen the argument due to its lack of connection to Alzheimer's disease (and thus, its lack of connection to the conclusion), but an answer choice that strengthens a premise can also strengthen an argument.

I would go further and say that answer choice (E) is largely irrelevant even to the premise that Creutzfeldt-Jakob disease is caused by a virus. It doesn't provide any support one way or the other. The fact that blood from healthy rats doesn't cause Creutzfeldt-Jakob disease in other rats only shows that blood transfusions alone don't cause the disease. It doesn't show what does cause the disease. In sum, answer choice (E) is consistent with 1) Creutzfeldt-Jakob disease being caused by a virus, 2) Creutzfeldt-Jakob disease not being caused by a virus, 3) Alzheimer's disease being caused by a virus, and 4) Alzheimer's disease not being caused by a virus.

You are on the right track. Try the method I modeled of asking yourself, if this answer choice is true: What can be true? What is likely to be true? What must be true? What must be false?

[dreamingofwharton]

Hi,

I understand why (D) is correct but still not very clear to eliminate (E)

(E) Blood from rats without Creutzfeldt-Jakob disease produced no symptoms of the disease when injected into other experimental rats.

Study is that blood was taken from humans and injected into rats, blood should have virus which caused that Creutzfeldt disease in rats.

Now, option (E) implicitly says that blood from rats without Creutzfeldt didn't have any virus, doesn't this increase our confidence in the conclusion by eliminating another alternate cause of virus presence? Had virus been already present in blood of these rats before injecting into them from humans then it would have weakened the conclusion that blood of humans had virus and caused the disease.

Please let me know what I am thinking wrong in my reasoning.

[Jeff Wren]

Hi dreaming,

The key to solving strengthen questions (like many LR questions) is to focus on the conclusion of the argument. The conclusion here is that Alzheimer's disease might be caused by a virus. Our answer really needs to focus on Alzheimer's disease. Creutzfeldt-Jakob disease is only relevant in the argument in so far as it relates to Alzheimer's disease, since that is what the conclusion concerns.

Answer E states that blood from rats without Creutzfeldt-Jakob disease produced no symptoms when injected into other rats. This supports the idea that Creutzfeldt-Jakob disease is caused by a virus. However, we already know that Creutzfeldt-Jakob disease is caused by a virus as that is directly stated in one of the premises. The problem is that this doesn't connect to the idea that Alzheimer's disease might be caused by a virus.

Answer D, on the other hand, directly connects Creutzfeldt-Jakob disease with Alzheimer's disease, which strengthens the conclusion.

[dreamingofwharton]

Hi Jeff,

Thanks for the response, much better now, however, wanted to confirm one reasoning to eliminate E.

Can we also say that (E) is wrong because the point of the study is the initial human-to-rat transmission. Whether rats can infect other rats with CJ disease doesn’t tell us anything about whether HUMAN blood contained a virus, or whether that virus is connected to Alzheimer’s. Overall, (E) doesn't provide us helpful info to increase our belief in the conclusion that virus caused the Alzheimer's.

[Dana D]

Hey dreaming,

The rat to rat transmission is definitely another issue with answer choice (E), yes. Perhaps if the rats with the disease could infect other rats this would strengthen the stimulus, but that would depend on that information being applicable to humans, which is not a given, so yes I would flag that issue with answer chioce (E) as well! Good job