PrepTest 117, Section 2, Question 20
Scientist: My research indicates that children who engage(45 more words not shown)
Which one of the following,(9 more words not shown)
- AMany impulsive adults(6 more words not shown)
- BIt is not(9 more words not shown)
- CChildren are often(13 more words not shown)
- DMany people exhibit(11 more words not shown)
- EThe gene variant(16 more words not shown)
Reading the argument
That is a suggestive connection. I'm just not ready to call it a cause yet. The scientist finds that impulsive children are twice as likely as other children to have a particular gene variant. The variant increases sensitivity to dopamine. It's reasonable to investigate whether that has something to do with a tendency toward thrill-seeking. But twice as likely doesn't mean every impulsive child has the variant or that no other child does.
What we’re looking for
My initial concern is the usual one about an observed connection: have we shown what produces what, or could something else explain the pattern? I don't yet have a specific alternative explanation. The question asks us to challenge the argument, so I'll look for a fact that makes this research a less reliable basis for the causal conclusion. We don't have to prove the gene has no effect; we need a reason to doubt that this study establishes the proposed relationship.
Working the answers
- A
Impulsive adults without unusual dopamine sensitivity don't rule out a causal contribution from this gene variant. A behavior could have several causes; some people might show it for a different reason. The scientist hasn't claimed that everyone with impulsive behavior must have this sensitivity, and the evidence concerns a comparison among children. These adult exceptions don't undermine that comparison in the direct way B does.
- BCorrect
This attacks the foundation of the comparison rather than offering the alternative cause I was considering. If impulsive behavior can't reliably be distinguished from other behavior, how did the scientist reliably separate the impulsive children from the other children?
The reported difference depends on those groups being meaningfully identified. If children are classified inconsistently, the difference in gene frequency becomes a much less reliable basis for a claim about an inclination toward thrill-seeking.
Be precise: B doesn't say impulsive behavior is imaginary. A real type of behavior can still be difficult to identify reliably. The problem is the reliability of the categories used in the research, not proof that the behavior doesn't exist.
- C
This concerns adults describing children's impulsive acts as thrill-seeking. It doesn't establish that the scientist cannot identify impulsive behavior or that the observed gene comparison is unreliable. The passage already describes the childhood behavior as similar to adult thrill-seeking. Merely reporting that adults use a related label doesn't refute the proposed connection.
- D
People's behavior can change as they grow older without showing that a gene variant has no causal relationship to a behavioral inclination. The scientist doesn't claim every childhood tendency persists unchanged into adulthood. D challenges a claim about lifelong consistency that the argument hasn't made.
- E
Association with other behaviors doesn't eliminate association with this one. A gene variant could be related to several tendencies at once. E doesn't say the other behaviors explain away the thrill-seeking connection or show that it isn't causal. It just adds relationships that could coexist with the one under investigation.
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