V06-31

Question

Aldolase is a protein found in the brain. In an experiment, subjects who consistently chose sweetened drinks when offered a choice between salty and sweetened drinks were found to have significantly higher concentrations of Aldolase in their brains than did subjects who consistently chose salty drinks over sweetened drinks. This observation strongly supports the conclusion that Aldolase causes subjects to crave sweetened drinks.
 
Which one of the following, if true, supports the argument the most?

A. The craving for sweetened drinks does not invariably result in choosing those drinks over salty drinks.
B. The brains of the subjects that consistently chose to drink sweetened drinks did not contain significantly higher concentrations of another chemical, which is found to cause cravings for sweet food among mice, than did the brains of subjects that consistently chose salty drinks.
C. The chemical components of Aldolase are present in both sweetened and salty drinks.
D. Concentrations of Aldolase detected in the brain are significantly higher after taking sweet beverages than those detected before.
E. Subjects that metabolize sugar less efficiently than do other subjects develop high concentrations of Aldolase in their brains.

Bunuel · Answer

Official Solution:

Aldolase is a protein found in the brain. In an experiment, subjects who consistently chose sweetened drinks when offered a choice between salty and sweetened drinks were found to have significantly higher concentrations of Aldolase in their brains than did subjects who consistently chose salty drinks over sweetened drinks. This observation strongly supports the conclusion that Aldolase causes subjects to crave sweetened drinks.
 
Which one of the following, if true, supports the argument the most?

A. The craving for sweetened drinks does not invariably result in choosing those drinks over salty drinks.
B. The brains of the subjects that consistently chose to drink sweetened drinks did not contain significantly higher concentrations of another chemical, which is found to cause cravings for sweet food among mice, than did the brains of subjects that consistently chose salty drinks.
C. The chemical components of Aldolase are present in both sweetened and salty drinks.
D. Concentrations of Aldolase detected in the brain are significantly higher after taking sweet beverages than those detected before.
E. Subjects that metabolize sugar less efficiently than do other subjects develop high concentrations of Aldolase in their brains.

Premise:  Correlation is seen between choosing sweetened drinks and higher concentrations of Aldolase.
 
 Conclusion:  Aldolase causes cravings for sweetened drinks.
 
A. The premise deals with a relation between Aldolase and  choosing  sweetened drinks. The conclusion is about a relation between Aldolase and  craving  for sweetened drinks. The missing link in the reasoning is the relation between  choosing  and  craving . This missing link, in other words the underlying assumption, in the argument is that  craving  leads to choosing. However option A merely states the opposite of this assumption and hence cannot be a statement supporting the argument.
 
 B. CORRECT.  For an argument X causes Y, the  weakening  statement could be Z causes Y (implying it's not X that causes Y). Therefore a  strengthening  statement could be Z does NOT cause Y. Here X = Aldolase, Y = craving for sweets, Z = another chemical (which is found to cause cravings for sweet food among mice) 
 
Thus this option confirms that another chemical which causes cravings for sweets in mice is NOT the reason for cravings of sweetened drinks among the subjects, and hence this option strengthens the argument that Aldolase indeed is the cause of the cravings.
 
C. This option supports the hypothesis why similar concentrations of Aldolase is found in the brains after taking sweetened or salty drinks, i.e. this option considers Aldolase concentration as the  effect  of some action, i.e., taking sweetened or salty drinks. Hence this option does not have any relevance to the argument because the argument is about Aldolase being the  cause  of cravings for sweetened drinks.*
 
D. This option is a weakening statement. For an argument X causes Y, a weakening statement could be Y causes X (reversal of causation). Here X = Aldolase, Y = craving for sweetened drink.
 
Thus this option establishes that taking sweetened drinks increases the concentrations of Aldolase and not the other way round, i,e. Aldolase does not cause the cravings for sweetened drinks.
 
E. Like option C, this option also considers concentrations of Aldolase as an effect of something, here, low metabolism of sugar. Hence this option does not have any relevance to the argument because the argument is about Aldolase being the cause of cravings for sweetened drinks.*
 
 *Note:  Nonetheless, cause-effect reversal is useful to be examined when dealing with weakening statements, as in option B above.

Answer: B

Bunuel · Answer

The question or/and solution has been revised and edited. Thank you  sayantanc2k  !!!

ShubhamKumar2967 · Answer

Bunuel,
How are we able to comprehend that the subjects and mice have similar functions, at least in terms of brain functioning?

lakshya503 · Answer

I did not quite understand the solution. Question - how are we supposed to draw the parallel between some chemical affecting mice and that chemical having the same effect in humans? It seems like a leap to arrive at this solution and the question does not hint at it.

kosukhov · Answer

Hi!

My 2 cents on that:

I had a similar thought when solving this one, but after spending some time on it, I came to the conclusion that:

Even though, as you mentioned, we can't definitively draw a parallel between mice and humans, there’s still a reasonable possibility that a chemical affecting mice could also influence humans. So ruling out that possibility can strengthen the argument by narrowing down Aldolase as the likely cause. 
 The other four options clearly don't work, so even if (B) feels a bit of a stretch, it’s still the best available support for the conclusion.

RonPurewal · Answer

Aldolase is a biochemical, not a trademarked product, so it should not be capitalized.

.

Addition of "in human subjects" is essential to give the answer choices the tight relevance that they need for the GMAT. (The answer choice about mice should be purged—see below.)

.

Choice B (the current version in the OP) lacks the tightly circumscribed relevant specifics that it needs to be a correct answer. This choice is at least quadruple-irrelevant:

/1/ Humans are not mice. We can't just assume that mouse physiology extends to humans. (Most aspects of mouse physiology noted in medical experiments do NOT, in fact, extend to humans. The primary use of mouse studies is to provide a low-stakes sample on which to test toxicity, not from which to make observations and just blithely assume that those observations will extend to humans.)

/2/ No indication at all that the chemical mentioned in choice B is ever present in humans.

/3/ The chemical causes mice to crave sweet   food  . Sweet food ≠ sweet drinks.

/4/ What if there are 999 other brain chemicals involved in the same decision set? On top of the previously listed triple layers of irrelevancy, choice B also requires the presumption—without any evidence or related reasoning—that the 2 chemicals mentioned (one in the passage, one in choice B) are the only 2 brain chemicals that play any significant role in mice brains' navigation of these consumption decisions.

.

Since the basic argument in the passage contains a "correlation therefore causation" fallacy, we ought to rule out one of the two other potential ways to explain the correlation. In other words, to SUPPORT the assertion that "higher aldolase —> salty over sweetened drinks"—where the arrow represents causation—we could do either of the following:

i • DISMISS the possibility that "salty over sweetened drinks —> higher aldolase";

ii • NEGATE the possibilitiy of some third factor that causes BOTH the preference for the salty drinks AND the elevation of aldolase levels.

This correct answer performs function "i" above:

Repeated consumption of salty drinks does not decrease aldolase concentrations in the brain.

If repeated consumption of salty drinks DID decrease brain aldolase, then the correlation in the original passage would be explainable by reverse causation. This choice rules out that reverse causation, and can therefore be substituted for choice B as the new correct answer.

(Choice D, of course, is a wrong-way answer. I've written the new choice B in terms of  salty  drinks—which are the  other  half of the decision pair (besides sweet drinks)—so that choice D can be left as-is. (GMAC won't write two choices that are just directly contradictory opposite directions of the same type of statement. Had I written the new choice B as "Repeated consumption of  sweet  drinks  does not raise  brain aldolase levels", choice D would've had to go or be reworked.)

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