#27 - Specific Reference, Parallel

[Administrator]

Please post below with any questions!

[ndimas]

Hi there! Can someone please explain how B is the most analogous to the manner which fMRI scans of brain activity are typically interpreted?

[AthenaDalton]

Hi ndimas,

The description of the subtractive method of fMRI brain imaging tells us that the researchers take two brain scans: one "baseline" scan when the brain is showing normal activity and one "research" scan which shows the brain focusing on a particular task. Then the the "baseline" scan is subtracted from the "research" scan to highlight the differences which, in turn, gives us our area of activity -- whatever part of the brain shows more activity once this subtraction is complete is the active area. The author points out that this is potentially flawed since even in the baseline scan, the brain is still active, so the subtraction could weed out some important area of brain activity.

Answer choice (B) also uses a sort of subtraction method to pinpoint when advertising is effective. In (B), a store saw more activity in only one season of the year as compared to the rest of the year, so the researchers subtract the regular season sales (baseline) from the busy season sales (research) to conclude that the ad campaign only draws in customers in the summer. The problem with this approach -- as in the passage -- is that customers buy items all year, so only focusing on the summer sales could obstruct some important info about how ads also drive sales in the winter, spring, and fall.

The other answer choices fall short of making a close analogy to the subtraction research study -- subtract the baseline snapshot from the research snapshot to conclude what works.

Hope this helps!

Athena Dalton

[Res Publica]

I struggled with between selecting (B) and (C). I see how (C) is correct, but I want to better understand why (B) is wrong. Is it because (C) would seem to compare residential to agriculture? (in our brain analogy, that would be akin to comparing one region of the brain to another, instead of taking a brain region's current activity and subtracting it from its normal level?)

[Adam Tyson]

Just to clarify, Res Publica, the correct answer here is B, while C is the one that causes some trouble. I think you've pegged why that's so with your explanation - answer C tells us nothing about any subtraction or baseline situation, but instead tells us that we start with a difference and then anticipate what difference there would be in the impact a particular "task" or event on those two regions.

Nicely done!

[goingtosomewhere]

Hello,

I just wanted to clarify a point that Athena made. When stating that "customers buy items all year" it's basically like the argument Uttal was making about the general metal activity? And is another implication of the advertisement that it could possibly be preventing winter, spring, and fall shopping numbers from dropping? I'm trying to understand better what role the advertisement plays in the analogy.

Thank you!

Hi ndimas,

The description of the subtractive method of fMRI brain imaging tells us that the researchers take two brain scans: one "baseline" scan when the brain is showing normal activity and one "research" scan which shows the brain focusing on a particular task. Then the the "baseline" scan is subtracted from the "research" scan to highlight the differences which, in turn, gives us our area of activity -- whatever part of the brain shows more activity once this subtraction is complete is the active area. The author points out that this is potentially flawed since even in the baseline scan, the brain is still active, so the subtraction could weed out some important area of brain activity.

Answer choice (B) also uses a sort of subtraction method to pinpoint when advertising is effective. In (B), a store saw more activity in only one season of the year as compared to the rest of the year, so the researchers subtract the regular season sales (baseline) from the busy season sales (research) to conclude that the ad campaign only draws in customers in the summer. The problem with this approach -- as in the passage -- is that customers buy items all year, so only focusing on the summer sales could obstruct some important info about how ads also drive sales in the winter, spring, and fall.

The other answer choices fall short of making a close analogy to the subtraction research study -- subtract the baseline snapshot from the research snapshot to conclude what works.

Hope this helps!

Athena Dalton

[Poonam Agrawal]

Hi goingtosomewhere!

Yes, customers buying items all year is analogous to Uttal's argument about general mental activity. As in, there are still things happening in other parts of the year and in other parts of the brain - a differential test doesn't tell us information about things that appear to remain the same as the baseline.

The implication you've described is absolutely correct. It is possible that the advertisement could be preventing shopping from dropping in other seasons. A closer analogy to the passage is simply the fact that someone might look at that differential shopper number and wrongly assume that people only shopped in the summer, and not in the other months. Both implications represent interpretation mistakes with differential scans.

The role that the advertisement plays in the analogy is similar to that of the cognitive task in the passage. It is the "stimulant" that leads to the changes occurring in the shopping/brain. Hope this helps!

[sblack1998]

Wow! I got so sidetracked on this question because of the word "typically" in the question stem. In the stimulus, the author mentions how these scans are "USUALLY interpreted as a map of the rate of oxygen use" and then later talks about "what is ACTUALLY [being] depicted." When I saw the word "typically" in the question stem I thought it was referring to how the "usual" interpretation was a "map of the rate of oxygen use" and so I was looking for an example of a map and/or rate of use in the answer, which led me to A or C. I chose C. (Facepalm).

[jeep180]

Wow! I got so sidetracked on this question because of the word "typically" in the question stem. In the stimulus, the author mentions how these scans are "USUALLY interpreted as a map of the rate of oxygen use" and then later talks about "what is ACTUALLY [being] depicted." When I saw the word "typically" in the question stem I thought it was referring to how the "usual" interpretation was a "map of the rate of oxygen use" and so I was looking for an example of a map and/or rate of use in the answer, which led me to A or C. I chose C. (Facepalm).

Hello, I think you are right. Lines 34-37 show how an fMRI is usually interpreted: people think that only the areas lit up are in use. But in fact, the areas that are lit up are merely more in use. Their error is thinking: “One region is especially active in a process. So only that region is active.”
We’re trying to find an answer that matches the incorrect reasoning of those who interpret fMRIs. So, we should look for something that says: “X is especially a factor. So only X is in play.” Most importantly, it should be a bad argument.
And only (B) matches. With brain scans, the thought process is: “During this emotion, only one area has an increase in activity. So only that area is involved”. Likewise “During the ad campaign, only one season had an increase. So only that season is affected”.

[Robert Carroll]

jeep180,

That's perfect, couldn't say it better myself!

Robert Carroll