PrepTest 127, Section 1, Question 14
Over 90 percent of the human brain currently(48 more words not shown)
Which one of the following(8 more words not shown)
- AThe argument presumes,(13 more words not shown)
- BThe argument presumes,(19 more words not shown)
- CThe argument infers(23 more words not shown)
- DThe argument infers(21 more words not shown)
- EThe argument presumes,(20 more words not shown)
Reading the argument
How did we get to “over 90 percent”? The author points to people with significant brain damage who show no discernible adverse effects. That does not give us a measurement of how much of the brain serves no purpose. And an effect that has not been noticed might still exist.
Then the argument makes another leap. Supposedly, tapping this unused portion of the brain would put many currently overwhelming problems within our ability to solve. But what could that portion actually do? Even if we accepted that it is unused, we would still need a reason to think it contains a reserve of creativity and innovation. Unused capacity is not automatically useful capacity.
What we’re looking for
There are several places to question the reasoning, so I would not force a single precise wording before seeing the choices. The flaw answer needs to describe a jump the author actually makes. The missing connection between allegedly unused brain tissue and valuable new problem-solving abilities is especially central to the final claim.
Working the answers
- A
This is tempting because we did question the move from no observed harm to no function. But A requires a much broader assumption: that the effects of brain damage are always easily detectable. The author need not assume that every effect of every kind of damage is easy to detect in order to treat the cited cases as evidence of unused capacity. A overstates the assumption instead of precisely describing that evidential gap.
- B
The conclusion concerns many problems becoming solvable, not every unsolved problem having just one cause. Some problems could remain unresolved because of political disagreement, lack of resources, or other obstacles. The author does not need to assume that a shortage of creativity is the only reason any problem remains unsolved.
- C
The author does offer evidence for the claim of unused brain tissue: the cases of significant damage without discernible adverse effects. We can question that evidence, but it is different from simply saying, “We don't know what these parts do, so they must do nothing.” C substitutes a different basis for the claim.
- D
The conclusion says that many problems will be within our ability to solve. It does not go on to infer that those problems will actually be solved. Having the ability and using it successfully would be different things, but D attributes a further step that this argument never takes.
- ECorrect
The supposedly unused parts are simply labeled a tremendous source of creativity and innovation. Where is the evidence for that description? Even granting that the tissue currently serves no purpose, it might not be capable of providing the particular abilities the author promises. The argument needs that creative potential to connect the unused tissue with solving difficult problems, and it has not established it.
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