PrepTest 129, Section 2, Question 14
Scientists have shown that older bees, which usually(58 more words not shown)
Which one of the following,(8 more words not shown)
- ABees that have(21 more words not shown)
- BThe brains of(18 more words not shown)
- CThose bees that(22 more words not shown)
- DIn some species(16 more words not shown)
- EThe brains of(21 more words not shown)
Reading the argument
Older bees have larger brains, but why? Perhaps their brains grow as they age. Or perhaps bees with larger brains are more likely to survive to old age. Either possibility could create an age difference without foraging being its cause.
The scientists also tell us that older bees usually forage, while younger bees tend newly hatched bees. Foraging requires greater cognitive ability. I can see the suggested explanation: doing the more demanding task might enlarge the brain.
But could the direction run the other way? Maybe bees whose brains are already larger are better able to forage. In that case, foraging would accompany the larger brain rather than produce it. We need a reason to distinguish the proposed effect of foraging from age, survival, or a preexisting difference.
What we’re looking for
The question asks us to weaken the causal claim. I'd look for evidence that bees can develop the larger brains without foraging, or evidence that something else explains the difference.
Working the answers
- A
This compares different amounts of foraging, and it is tempting to expect more of the activity to produce more growth. But the argument does not say the effect keeps accumulating indefinitely. A bee might gain the relevant brain size soon after starting and then level off. Equal sizes after short and long periods would still fit that possibility, so A leaves the proposed causal effect largely intact.
- B
An effect can last after its cause stops operating. If foraging enlarged a bee's brain, the enlargement might remain when the bee took on another task. B concerns whether the change reverses, while the conclusion concerns what originally produces the change.
- C
Both groups forage; they differ in how far they travel. The argument does not claim that longer journeys produce larger brains than short ones. Equal brain sizes among those groups therefore do not separate foraging from nonforaging as a cause.
- D
A marginal increase is still an increase. The author is trying to explain why older bees have larger brains, not prove that the difference must be enormous in every species. D changes the size of the difference without identifying a different cause.
- ECorrect
Now we compare bees of the same age, some of which forage and some of which never learn to. Their brains are the same size. The larger brains appear even without the activity the author credits with producing them.
That makes ordinary aging or another shared factor more plausible as an explanation. E does not prove that age itself is the cause or that foraging can never affect a brain. It does substantially weaken the inference that foraging explains the older bees' increased brain size.
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