#26 - Global Reference, Must Be True

[brcibake]

I did not claim C to be a loser, but thought D was a better choice. To me, C was parallel with what the author was arguing against.

[Adam Tyson]

Careful, brcibake! The author never says that there is no difference in oxygen consumption rates throughout the brain. Just the opposite - his description in lines 34-46 tells us that there is definitely differentiation. The problem is that some people may interpret the scans as showing that some areas have no activity when in fact they have some, but just less than others.

The problem with answer D is that the passage says nothing about any area of the brain having high rates of activity all the time. It does say that the entire brain is active all the time, but nothing about "high" rates of activity. That word kills answer D.

Every word counts!

[mN2mmvf]

Hi,

I chose (D), but didn't love it (and understand your reasons against it, all of which I did consider). But I don't quite understand (C).

My understanding of the subtraction method led me to think (C) was not possible. As far as I understood, the author was arguing that the problem with the subtraction method is that it leads us to incorrectly think that the normal levels of brain activity are zero, because the the method entails 1) measuring the baseline level of activity of all parts, and 2) then measuring the level of activity of all parts during a stimulus, and 3) subtracting 1 from 2 to find the effect of the stimulus.

So let's say that the brain has four areas, M, N, O, and P. The normal levels of activity in each are 25, 50, 30, and 20. When exposed to a stimulus, area P "lights up" and has an activity level of 40, twice its normal rate. Using the subtraction method, we'd see levels of 0, 0, 0, and 20. Thus, it looks like P is the center of all of the activity for the given stimulus, when in fact it's possible that some of those other normal activity levels are contributing to the mental activity.

I thought (C) was wrong because even though its lit-up-reading was 20, area N still had higher metabolic activity in absolute terms, absent the subtraction method. (I thought this would be a classic LSAT error! So I eliminated it even though I didn't love D, because I thought it was surely meant to look attractive while committing this very error.)

Perhaps your response will be, Answer choice (C) says only that "the areas of the brain that are most metabolically active show a rate of oxygen use that is higher than the rest of the brain," and even if I'm considering the absolute levels only, the area that is most metabolically active actually is area N, and that is still higher than P even when P is lit up, and thus is higher than the rest of the brain. And thus (C) is correct.

But if that's the case, why does answer (C) talk about activity specifically "during the performance of certain cognitive tasks"? The passage overwhelmingly led me to think that "certain cognitive tasks" would be the stimuli researchers were testing. But even if that's a wrong assumption, why do the baseline levels of cognition in every person's brain constitute "certain cognitive tasks"? Perhaps the brain is just passively, metabolically processing oxygen like every other organ in the body does, without conducting any cognitive tasks at all? (Those organs, needless to say, do not conduct cognitive tasks.)

Thanks!

[James Finch]

Hi MN,

(C) says that the areas of the brain most metabolically active also show higher oxygen use, at least during certain cognitive tasks. The passage itself implies that this holds true at all times, and rate of oxygen use is essentially synonymous with how metabolically active that portion of the brain is. So if (C) is true all the time, or under all conditions, it would also be true under certain conditions. So (C) remains correct with or without the stipulation about dealing only with periods of performance of certain cognitive tasks.

Hope this helps!

[cecilia]

Twice, i have done this passage and gotten just this exact question wrong ( grrrrr). Most recently I eliminated (C) for the same reason that the initial poster above ( " brcibake " ) did, because it seemed to go against the author's main point. While Adam's response and clarification really helped, I wonder if my approach to this question was completely off.

As a "Global" q., i thought our first instincts were to keep **author's view*** and main point and big picture in mind. And yet, that frame of reference - particularly the author's opinion - ended up hurting me in this instance. Was it because this question was more of a Concept Reference q., and hence, I should have been more open to going back to the passage to dig out a specific detail/concept and cross-reference it????

Again, I understand why (C) is the correct answer. I just need help on better approaching this type of q next time.

Thanks in advance for your time....

[Adam Tyson]

Questions like this one - broad, open, global (about the entire passage rather than any specific lines or concepts) - are virtually impossible to prephrase, cecilia, and for that reason my advice on the best approach is to be very, very forgiving of the answer choices. By that I mean that you should go into the answers with a very broad prephrase - maybe just reminding yourself of the main point and overall tone or author's viewpoint - and then be willing to keep every answer as a contender unless you know for certain that it is unsupported either because it is based on new information never discussed (and be careful there not to trust your memory too much) or because it definitely runs counter to what the author sought to tell us. For questions like this, I expect to have three contenders, and I am thrilled if I have only two. I don't trust my memory, because I know how clever the test makers are at exploiting that approach and tricking me into remembering things that weren't there and forgetting things that were. That's their superpower!

Then, my next step after sorting the answer choices into losers and contenders is to return to the passage to find evidence to support one of them, or to eliminate one of them. If I have a favorite answer, I go find something to prove it's right; if not, I pick my first contender and go look for evidence for or against it, and if I find no evidence either way then it is a loser (because no evidence means it is not supported).

That's the whole ball game right there, cecilia - gather and use evidence for or against the contender answers. That's the skill you are being tested on - not how well you understood what you read, or how good a memory you have, but how well you can support an argument based on the evidence presented. The evidence is in the passage, so plan on digging it up as often as needed to make your case. That's your mission! Good luck!

[cecilia]

Thank you!

[sylvia11]

Is (E) wrong because we don't know whether anger would show up in "several regions"of the brain when looking at it using the subtractive method? I know the purpose of the passage is to show that the method relies on questionable assumptions and interpretation of the results, but using the method, wouldn't brain activities (e.g. feeling angry) show "lit up" areas of the brain?

[Adam Tyson]

Exactly right, sylvia11! We don't know that "several areas" would light up using the subtractive method in this case. Maybe just one area would do so?

[goingtosomewhere]

Could someone explain to me why B is incorrect? I was deciding between B and C and chose B because I was thinking that by using the subtractive method, the areas that are not engaging in the task would not have a differential rate change and hence be zero (which according to the author is not zero and is still involved), according to the modular theory. Thank you!