Critical Reasoning

22. A scientist made three observations: (1) in the world's temperate zones, food is more plentiful in the ocean than it is in fresh water; (2) migratory fish in temperate zones generally mature in the ocean and spawn in fresh water; and (3) migratory fish need much nourishment as they mature but little or none during the part of their lives when they spawn. On the basis of those observations, the scientist formulated the hypothesis that food availability is a determining factor in the migration of migratory fish. Subsequently the scientist learned that in the tropics migratory fish generally mature in fresh water and spawn in the ocean.

Which one of the following would it be most helpful to know in order to judge whether what the scientist subsequently learned calls into question the hypothesis?

(A) whether in the world's temperate zones, the temperatures of bodies of fresh water tend to be lower than those of the regions of the oceans into which they flow

(B) whether the types of foods that migratory fish eat while they inhabit the ocean are similar to those that they eat while they inhabit bodies of fresh water

(C) whether any species of fish with populations in temperate zones also have populations that live in the tropics

(D) whether there are more species of migratory fish in the tropics than there are in temperate zones

(E) whether in the tropics food is less plentiful in the ocean than in fresh water





I got the question right. But I'm not sure why B is wrong here. My reasoning with B goes like this:

If the fish in tropical area moved into the ocean or fresh water not in accordance with food availability (which is author's hypothesis), then that would definitely help to question his hypothesis.

Please explain.

The OA is E

IMO E

The scientist says...
in temperate zones, food is more plenty in oceans than it is in fresh water. so there migratory fish get matured & well nourished in ocean and spawn in fresh water.
But in his hypothesis he mentions tropics instead of temperate zones & keeps remaining data as is.

So In order to make sure his hypothesis is questionable, we need to know whether food is less plentiful in the ocean than in fresh water in tropics just like temperate zones. If we know this answer then we can say,whether or not his hypothesis is applicable to temperate zones.

user123321

Yes, I know why the correct answer is E. I asked about B, not E.

Got a PM on this one...

"the scientist formulated the hypothesis that food availability is a determining factor in the migration of migratory fish."

So we see that Answer Choice B is not correct because we are really interested in the availability (basically the quantity) of food and not the "type" of food.

So, "(B) whether the types of foods that migratory fish eat while they inhabit the ocean are similar to those that they eat while they inhabit bodies of fresh water" is not correct. The types of food do not have to be the same in the two places - nor does the foods have to be dissimilar - it is the quantity that counts.

Really it is as simple as that...every word matters in critical reasoning and in this case the hypothesis is about availability of food.

Hope it helps!

David, thanks for your reply, but it's still not clear.

In answer choice B we are given an alternative cause of fish behavior, thus weakening the author's conclusion. How come that this reasoning is wrong?

Now, I do understand why E is OK. I don't understand why B is wrong.

In answer choice B we are given an alternative cause of fish behavior, thus weakening the author's conclusion. How come that this reasoning is wrong?

But choice B does not give you an alternative cause for this behavior. By the way, this is not strictly a weaken question, but a "most useful to know"

Let me try from a different angle.

What we are looking for here is to see whether the new information fits the current hypothesis. The hypothesis is "the scientist formulated the hypothesis that food availability is a determining factor in the migration of migratory fish." This was based upon the already stated fact that in the temperate zones food is more plentiful in the ocean and the fish go to the ocean during the phase when they need more nutrients.

So the hypothesis fits the temperate zones quite well. But then in the tropics we have this new information that the fish migrate in the opposite direction. They go to the fresh water to eat and the ocean just to spawn. The question basically asks you "what information will help determine if this new observation fits the hypothesis or not?"

You say that you understand why E works, but others may not. E is correct because we already know that the in the temperate zones the fish go to the place with more nutrients to grow and the place with fewer nutrients to spawn. If choice E is there then we will know if the pattern holds in the tropics. This is a PERFECT answer.

Now choice B is not. What if I answer "Yes" the food in the ocean is similar to the fresh water"? Does this help determine if the pattern holds? No. It does not. B has nothing to provide for us. We need to know if the fish follow the quantity of food or not and B is not helpful on this count.

In my earlier response I was telling you a way to see these things on test day.

In general you really have to understand that in critical reasoning words matter. Think about critical reason like QUANT only instead of numbers you are using words.

So if I have a quant problem and I say " X + Y = 150" and then I ask "in order to solve this problem what would be most helpful?" 1) x = 50 2) z = 75. It is pretty clear that "x = 50" is much more useful because x is actually mentioned in the problem. Telling me about "z" is not useful because "z" is not a part of this. You could say, "Well I am trying to solve for two letters so any information about letters is useful" but of course that is not true. You are working with specifics.

The exact thing is true here as well. Remember that the conclusion (hypothesis) that we are working with is "the scientist formulated the hypothesis that food availability is a determining factor in the migration of migratory fish."

Now the part that I have in bold above "food availability" is key here. This problem relies on that phrasing. That is the factor in the migration. You cannot just say that it is "food" - it is "availability" which I read as "quantity" or simply "is there enough food or not."

Choice B does not mention quantity. "(B) whether the types of foods that migratory fish eat while they inhabit the ocean are similar to those that they eat while they inhabit bodies of fresh water"

"Types of food" is not "food availability" any more than "x" is "z."

This is crucial for everyone to understand who wants to be good at critical reasoning. Words have as much meaning as numbers and especially the words in the conclusion or hypothesis.

paraphrase: More food for maturing. Less food for spawning. In tropics - More food - Fresh water. Less Food - Ocean.

E answers this question.
B the type of food is beyond the scope of the facts mentioned in the para.
Hence E it is.

I think I got it why (B) is not correct.

First of all, what will the correct answer accomplish?

Which one of the following would it be most helpful to know in order to judge whether what the scientist subsequently learned calls into question the hypothesis?

In other words, the correct answer would provide the info on why the second observation questions the scientist's hypothesis; i.e., the second observation will weaken his hypothesis in light of the new information provided by the correct answer.

(B) whether the types of foods that migratory fish eat while they inhabit the ocean are similar to those that they eat while they inhabit bodies of fresh water

If we answer 'yes' to this question, will the second observation weaken the hypothesis?

No. If the food is similar everywhere, then it doesn't refute the hypothesis that fish travel in accordance with the availability of food.

If we answer 'no' to this question, will the second observation weaken the hypothesis?

No. Imagine that in the ocean fish eat mollusks type A, and in fresh water they eat mollusks type B. If for the growing phase of their life they need mollusks type A, and these mollusks are available in the ocean in temperate zones and in fresh water in tropics. Fish behavior in tropics is again explained by the hypothesis, and the hypothesis is not refuted by this info.

Therefore, knowing the information from (B), will not help the second observation to refute the hypothesis.

David, I have some reservations about your reasoning. In your analysis you haven't considered answering 'no' to the question in (B). And that was the thing that bothered me all the time.

nonamee -

The great thing is that you have worked it through for yourself and you have come to your own reasons why B is not correct.

Don't be troubled by my reasoning -- if you have found a way to explain it to yourself that is the thing.

Way to stick with it.

David and others, thanks for your responses.