Skywalker18 wrote:
deepti1206 wrote:
Scientist: My research indicates that children who engage in impulsive behavior similar to adult thrill-seeking behavior are twice as likely as other children to have a gene variant that increases sensitivity to dopamine. From this, I conclude that there is a causal relationship between this gene variant and an inclination toward thrill-seeking behavior.
Which one of the following, if true, most calls into question the scientist's argument?
A) Many impulsive adults are not unusually sensitive to dopamine.
B) It is not possible to reliably distinguish impulsive behavior from other behavior.
C) Children are often described by adults as engaging in thrill-seeking behavior simply because they act impulsively.
D) Many people exhibit behavioral tendencies as adults that they did not exhibit as children.
E) The gene variant studied by the scientist is correlated with other types of behavior in addition to thrill-seeking behavior.
Source: LSAT
Does not OA(B) doubt the validity of the premise?
My research indicates that children who engage in impulsive behavior similar to adult thrill-seeking behavior are twice as likely as other children to have a gene variant that increases sensitivity to dopamine
Generally, in weaken questions, we can challenge an assumption (link between premise and conclusion).
generis , other experts - please enlighten
and
AdityaHongunti ,
The LSAT and GMAT differ in this area.
GMAT
almost never attacks the premises.
The LSAT attacks the premises more frequently than the GMAT does.
• I suspect that the GMAT does not offer attacks on premises very often because
an attack on a premise is too "easy."
• That is, spotting a weak premise that then weakens the conclusion is not very difficult.
-- If a premise is weakened, we merely must:
1) compare any answers we have not eliminated, and
2) be sure that the weakened premise indeed weakens the conclusion
(I am hedging a bit in this sentence. Sometimes the way that a premise is weakened on the
LSAT is not enough to kill the conclusion.)
You are both correct.
Answer B attacks the premise. Further, Answer B effectively attacks the premise.
-- AdityaHongunti wrote: In option B arent we challenging a premise??
Yes. The premise is faulty.
-- Skywalker18 wrote: Does not OA(B) doubt the validity of the premise?
Yes. The premise is not valid.
If we weaken a premise, then we will probably weaken the conclusion.
• Effectively attacking the premiseScientist: My research indicates that children who engage in impulsive behavior similar to adult thrill-seeking behavior are twice as likely as other children to have a gene variant that increases sensitivity to dopamine. From this, I conclude that there is a causal relationship between this gene variant and an inclination toward thrill-seeking behavior.
If a child engages in impulsive behavior [similar to ABC],
that child is more likely to have a gene variant.
That gene variant increases sensitivity to dopamine. (Let's call that gene variant "D")
[
Assumed, tacit, or implied. Not stated]:
Because impulsive behavior in children is similar [enough] to thrill seeking behavior in adults [that characteristics of these children will be present in those adults],*
and
because impulsive behavior in children often indicates the presence of gene D,I conclude that IF thrill-seeking behavior exists (result), then gene D is present (cause)
Option B effectively attacks the premise: It is not possible to reliably distinguish impulsive behavior from other behavior.
It is NOT POSSIBLE (wow - strong) to reliably distinguish impulsive behavior from other behavior.
• NOT POSSIBLE to identify "impulsive" = any conclusions drawn from any group labeled impulsive are not validBad methodology: she cannot distinguish impulsive from non-impulsive behavior in children. Her group is random.
The "impulsive" group she has gathered can't even be called an "impulsive" group.
It's a collection of children. The end.
Being able to identify "impulsive" children is foundational to her later claim
She has chosen a group of what SHE says are IMPULSIVE children who are more likely to have some gene, D.
From that group, she has assumed quite a bit and concluded something.
But her methodology is bad.
Answer B says that she cannot truly identify impulsive children.
She does not even "get off the ground."
"Impulsive" does not mean anything. It is not possible to identify impulsive.
Conclusion smashed.
• TakeawayTakeaway: although very rare on the GMAT, IF you see an answer that attacks a premise,
and it is the only answer that weakens the conclusion, choose it.
Hope that helps.
*The Trap in THIS question: the assumption that "impulsive kids = thrill seeking adults." IRRELEVANT
In the background is the assumed similarity between impulsive behavior and thrill-seeking behavior.
The scientist says that she has examined a specially chosen population: children who behave impulsively.
From her observation of those children, who are likely to have gene D,
she draws a conclusion about adult thrill-seeking behavior
based on a vulnerable assumption that impulsive in children = thrill-seeking behavior in adults.
The words in pink above are what the GMAT would usually go after.
Given the answer choices in this question, those words are irrelevant. We don't get that far in the argument,
because she is NOT CAPABLE of choosing, accurately, children who are impulsive.
_________________
To live is the rarest thing in the world.
Most people just exist.
—Oscar Wilde
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33% (02:16) correct 
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