Logical reasoning PrepTest 141 · Section 4 · Question 20

Incorrect. This answer choice raises an alternative cause—other neurotransmitters also damage surrounding cells—thus weakening the argument.

Incorrect. This answer raises potential alternative causes—these other abnormal chemical levels could be causally related to the deterioration.

Incorrect. This answer seems like it eliminates an alternative cause. However, check the stimulus carefully—there's no indication that stroke patients have damaged or oxygen-starved nerve cells. That's only stated in the conclusion of the argument. Since this answer requires a jump, it doesn't strengthen the argument and can thus be eliminated.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
Leaking glutamate can kill nerve cells. Glutamate was higher in stroke patients who deteriorated over time. Therefore, glutamate leaking from damaged cells caused this deterioration.

Answer Anticipation:
While the stimulus tries to distract with science, at its heart, this is still a correlation/causation jump. Glutamate was found at higher levels in patients who were deteriorating after a stroke, so it must be the cause of the deterioration. The stimulus does provide information about how this causal relationship could happen, but it's still based on a correlation. As such, the common ways of strengthening a causal relationship apply here: eliminate an alternative cause; provide more examples of the cause and effect going together; show situations where the cause is absent and so is the effect.

Answer Explanation:
This answer eliminates a potential alternative cause. Note that the conclusion isn't just that glutamate is the cause of the deterioration, but that glutamate leaking from nerve cells is the cause of the deterioration. If the glutamate—which is established as being able to do this damage—can't come from anywhere else, then this source of the glutamate is more likely to be what is causing this damage.

Key Takeaway:
Science on the LSAT is meant to distract, not to be something that's tested. When you get an argument like this one that features unfamiliar language, scientific terminology, and medical conditions, skip trying to figure all that out and focus on the logic. In particular, questions about medicine and health tend to be about causation.

Incorrect. There's no need for these damaged nerve cells to survive—in fact, the more nerve cell damage there is, the more likely there is to be overall deterioration. This answer is out of scope of the argument.