PrepTest 153, Section 2, Question 18
Some killer whales eat fish exclusively, but others(74 more words not shown)
Which one of the following,(10 more words not shown)
- AKiller whales that(14 more words not shown)
- BUnlike harbor seals,(19 more words not shown)
- CWhen mature harbor(27 more words not shown)
- DYoung harbor seals(12 more words not shown)
- EIf a fish-eating(30 more words not shown)
Reading the argument
How do the young seals know which whales are safe?
The biologists propose that they don't know at first. Young harbor seals fear all killer whales, then learn that particular groups eat only fish and can be ignored. That sounds possible, but we need evidence for the learning process. Knowing that adult seals distinguish dialects does not by itself tell us how they acquired that ability.
My first thought is to test a young seal's reaction to a fish-eating whale. We could play recorded chatter from such a group. If an inexperienced young seal fears even whales that do not eat seals, that would fit the proposed broad initial aversion: the fear extends beyond the actual threat. If young seals instead distinguish safe from dangerous whales right away, that would be less helpful to the proposed starting point. I'd like evidence about how they react before learning which groups can be ignored.
What we’re looking for
For the strengthen question, I'd look for evidence of that progression from broad fear to learned comfort. It need not be the exact experiment I've imagined, but it needs to bear on how the seals come to distinguish the threats.
Working the answers
- A
What else the dangerous whales eat does not tell us how seals learn to recognize them. A whale could eat seals and other similarly sized mammals whether seals learn the dialect distinction or recognize it without experience. A leaves the proposed learning process untested.
- B
The fish's hearing is not the issue. We are already told that harbor seals distinguish whale dialects. Comparing their hearing with fish does not tell us whether their comfort around fish-eating whales develops through experience.
- CCorrect
I was looking for a test involving young seals, so “mature” might initially seem like the wrong group. Keep reading: these adults encounter an unfamiliar dialect from whales that eat only fish, and they flee. Even a mature seal does not automatically recognize every harmless group's chatter as safe.
That fits the learning account. The seal may have learned to ignore familiar fish-eating groups, but an unfamiliar sound still gets the default fearful response. Without experience with that dialect, the seal has not yet learned that these whales can be ignored.
C therefore supports the idea that comfort depends on familiarity and learning, rather than a built-in ability to identify every fish-eating group. It does not prove the entire developmental story, but it supplies evidence for the distinction the hypothesis makes.
- D
The hypothesis concerns how seals respond to killer whales. Their lack of a natural aversion to other predators does not show whether their initial fear of whales later gives way to learned comfort with particular groups. Different predators could produce different responses.
- E
This does show a kind of learning: after an attack, a seal becomes afraid of a dialect that other seals do not avoid. But that is the acquisition of fear after a bad experience. The hypothesis we are testing starts with fear and explains how seals learn to stop fearing safe groups.
E could help explain why a particular seal avoids a normally harmless group. C more directly supports the proposed need to learn which groups can safely be ignored, because even mature seals flee harmless whales whose dialect they have not learned.
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