PrepTest 151, Section 3, Question 1
Researchers put two electrodes in a pool that(71 more words not shown)
The statements above, if true,(8 more words not shown)
- AIn the wild,(6 more words not shown)
- BVibrissal crypts enable(5 more words not shown)
- CDolphins do not(12 more words not shown)
- DElectric fields interfere(8 more words not shown)
- EUnder normal circumstances,(7 more words not shown)
Reading the argument
The dolphin reacts when the electricity is on. What lets it detect the change?
The first part of the experiment gives us a useful comparison. With the electrodes activated, the dolphin swims away. With them off, it acts normally. That suggests it can sense something about the electric field, even though we haven't yet identified how.
Then the researchers cover the small organs on its snout. I'd expect that to matter if those organs help the dolphin sense the electricity. And the result fits: with the organs covered, the dolphin stops swimming away when the field is activated.
What we’re looking for
We're asked for the best-supported conclusion. The natural connection is that the vibrissal crypts help dolphins sense electric fields. We don't need to invent an objection to a sensible inference.
Working the answers
- A
This experiment uses a weak electric field in a pool. It doesn't tell us whether dolphins encounter strong fields in the wild. A adds both a different setting and a different field strength without evidence for either.
- BCorrect
Covering the crypts removes the dolphin's usual response to the electric field. That supports the idea that these organs enable the dolphin to sense the field. We have a change to a particular body part followed by a change in the relevant behavior, which gives us a reason to connect the two.
- C
We aren't told that the dolphin was trained to avoid electric fields. Nor does the observed avoidance establish whether it was learned or instinctive. C makes both claims about training and instinct when the experiment is about which organs allow detection.
- D
Detecting electricity needn't be a malfunction. If sensing electric fields is what these organs normally do, the dolphin's response could show them working properly. We aren't given evidence that the field disrupts their normal operation.
- E
Before the shield is added, the dolphin responds differently when the field is activated. That supports an ability to sense it, not an ordinary inability. The loss of the response comes after the researchers cover the organs; we shouldn't treat that altered condition as the normal one.
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