LSAT 90 - Section 4 - Question 14

This is a Strengthening question.

The psychologist's argument uses scientific reasoning, so we have a phenomenon and a hypothesis. The stimulus describes some observations, which can easily sound like an experiment. If interpreted as an experiment, it's a pretty badly designed experiment. So thinking about what controls we need to improve this "experiment," in other words, contrasting this with what an ideal experiment would look like, will help you solve this question.

The stimulus says most people's blood pressure rises when they talk, but extroverted people experience milder surges when they speak than do introverted people, for whom speaking is more stressful. So we have kind of a classic setup in the premise with two different groups of people and two different results. And the conclusion, or the hypothesis, is that this suggests that blood pressure increases result from the psychological stress of communicating rather than from the physical exertion of speech production.

This is strange. What if physical exertion is something that does affect blood pressure? It sounds reasonable to say that this might be a competing explanation that we would want to examine. If the psychologist had said that it is stress that causes blood pressure to increase and not, for example, the color of the hat someone is wearing, then sure. It makes sense that we would not examine the color of people’s hats since this is unlikely to affect blood pressure.

But the conclusion is ruling out physical exertion while the premise did not give us reasons to do so. In fact, physical exertion is not mentioned at all. And that is why this is a badly designed "experiment." It is not really even an experiment, but rather just an observation, as it does not control for physical exertion or anything else, for that matter. Imagine how weak this argument would be if introverts happened to physically exert more when they spoke than extroverts. Now not only does stress vary with blood pressure, physical exertion also varies with blood pressure. How can you say it is the stress, and not the physical exertion, that is causing the surge in blood pressure?

If you really wanted to figure out if it is psychological stress that causes increases in blood pressure, you would collect a bunch of people and randomly split them into two groups. You would not care if they were introverts or extroverts because these distinctions only mattered since they were thought to be good proxies for the speakers’ stress levels. The conclusion wasn't that introversion caused an increase in blood pressure. It was that stress caused the increase. And because the groups are totally random, people who do a lot of physical exertion and people who do not would be spread out across the two groups as well. Now you have controlled for physical exertion.

And then you intervene in one of the groups. It does not matter which one because they are equalized at the moment. You intervene by stressing out one of the groups as they speak (maybe by inducing conversation on controversial topics), and whatever differential blood pressure you observe, you can be pretty sure it was due to your psychological intervention. That is how you design an ideal experiment.

So you have two options if you want to strengthen this crappy argument. One option is to control for physical exertion: say that the amount of physical exertion is the same for both introverts and extroverts. Another is to say that physical exertion simply does not matter for blood pressure, just as the color of somebody’s hat does not matter.

Correct Answer Choice (D) strongly suggests that physical exertion doesn't matter. On first blush, (D) might seem irrelevant because it does not mention introverts, extroverts, or blood pressure. This is why I generally try not to anticipate answers in Strengthening or Weakening questions, especially in scientific reasoning. LSAT writers can always think of things I cannot think of, and I might be digging myself into a hole by trying to anticipate the answer.

(D) says deaf people experience increased blood pressure when they sign, i.e., communicate, but no change when they move their hands for any other reasons. So (D) is suggesting that it is not the physical exertion that is causing blood pressure to increase. If it were, you would expect to see an increase in both situations.

Do you see how physical exertion, while not equalized, has now at least been somewhat accounted for? (D) does not control for differences in physical exertion between the two groups (for example, it could still be the case that introverts move their hands more than do extroverts) but it does strongly suggest that even if there were differences in physical exertion, it would not be relevant, like the color of your hat.

So what is causing this blood pressure increase? In one situation, they are communicating, and in the other, they are not. So (D) is in fact also hinting that the stress attendant with communication might be causing blood pressure to increase. So (D) is great. Even with (D), you can still poke holes in the argument, but this is okay. In Strengthening questions, you just need to make the argument a little bit better.

Answer Choice (C) says introverted people who do not have chronically high blood pressure often sense the rises in blood pressure that occur when they speak in conversation. So there is a subset of introverts who do not have chronic high blood pressure, and this subset can sense their blood pressures go up. Maybe they feel flushed, dizzy, etc. This doesn't help the argument. Imagine if this group was not so sensitive and could not sense this increase. This would not change the fact that the blood pressure for this group still went up.

In addition, how does this group of introverts relate to introverts in general? And what about introverts who do have chronically high blood pressure? Are they as sensitive? What about extroverts who do or do not have chronic high blood pressure? (C) is silent on all of these questions and completely useless.

Answer Choice (E) is a little better than (C) in that at minimum, it is a comparison. (C) just told us something about a random subset of introverts, but (E) says extroverts are more likely to have chronically high blood pressure than are introverts. On top of that, extroverts are also more likely to take medication to lower their blood pressure.

So (E) is actually kind of relevant, and if anything, it is revealing another hole in the reasoning. It is telling us that extroverts are potentially carrying in this baggage that could undermine the conclusion. If extroverts are taking medication to lower their blood pressure, the observed difference in blood pressure between the two groups could just have been the result of this medication. (E) is offering a competing explanation for why the extroverts’ blood pressure did not go up as much. And I rarely say this, but if this were a Weakening question, I think (E) would actually be a great answer choice.

Answer Choice (A) is kind of interesting in its relationship to (E). (A) says medications designed to lower blood pressure do not keep people who take them from experiencing blood pressure fluctuations when speaking. We saw how (E) weakened the argument by presenting a potential alternative hypothesis. (A) is addressing this very weakness by saying that the extroverts’ medications do not prevent blood pressure surges. Maybe they are designed to just lower ambient levels of blood pressure and do not work when your blood pressure surges.

I do not think (A) is very relevant without its relation to (E), because when we consider (A) alone, we do not even know which group is taking this medication. So where (A) might be relevant is precisely when it saps energy away from (E). But notice how we are now just back to where we were in the beginning. The argument is not any stronger.

Answer Choice (B) says that in general, the lower one's typical blood pressure, the more one's blood pressure will increase under stress. Fair enough, but it seems like (B) is ignoring the argument and just reiterating the conclusion that stress makes your blood pressure go up. This is a classic wrong answer choice in Strengthening questions. It just leaves our argument as good or bad as it ever was.

First, we do not know who has the lower baseline blood pressure since the stimulus just said extroverts experience a milder surge than introverts. And even if we say that the higher surges for introverts were due to a lower baseline and milder surges for extroverts were due to a higher baseline, we are still left with the original hole in the argument. We do not know if it is the stress or the physical exertion that causes surges in blood pressure.