Q22 - Fish with teeth

[ManhattanPrepLSAT1]

Question Type
Flaw

Stimulus
The argument concludes that the algae-scraping specialization evolved more than once. Why? Becuase genetic tests show that the algae-scraping fish are not closely related. And if they were closely related then the algae-scraping specialization evolved only once.

Anticipation
This argument relies on negated logic.

Correct Answer
Answer choice (C) describes the flaw of negated logic. Both negated logic and reversed logic is described in Flaw question answer choices as "mistaking a sufficient condition for one that is necessary."

Incorrect Answers
(A) correctly describes the wrong flaw. Causation is never introduced in this argument. A conditional relationship (if/then) represent a correlation, not causation.

(B) correctly describes the wrong flaw. This argument is quite close the flaw described in this answer choice but the argument is not based on unproven evidence but rather the negation of trigger in an if/then relationship.

(D) correctly describes the wrong flaw. There is no evidence that suggests something was indeed likely.

(E) correctly describes the wrong flaw. While an appeal to an innappropriate authority is flawed reasoning, the argument doesn't conclude that what the biologists say is true.


#officialexplanation

[kkate]

Can someone help me explain why it's C? Does C simply refer to reverse causality?

Premise: If closely related -> evolved once
Conclusion: Not closely related -> evolved more than once

Flawed because the author mistakenly reverse the premise to arrive at the conclusion? or is there some other sufficient and necessary condition I'm missing?

Thank you in advance!

[Hbegum1]

Question Type
Flaw

Stimulus
The argument concludes that the algae-scraping specialization evolved more than once. Why? Becuase genetic tests show that the algae-scraping fish are not closely related. And if they were closely related then the algae-scraping specialization evolved only once.

Anticipation
This argument relies on negated logic.

Correct Answer
Answer choice (C) describes the flaw of negated logic. Both negated logic and reversed logic is described in Flaw question answer choices as "mistaking a sufficient condition for one that is necessary."

Incorrect Answers
(A) correctly describes the wrong flaw. Causation is never introduced in this argument. A conditional relationship (if/then) represent a correlation, not causation.


- How is it that conditional relationships are not causations? I thought "if" was "cause" and "then" was "effect"? Like in the sentence, "If I have money, then I will buy food" is causation, not correlation. I'm so confused. Some please help!

(B) correctly describes the wrong flaw. This argument is quite close the flaw described in this answer choice but the argument is not based on unproven evidence but rather the negation of trigger in an if/then relationship.

(D) correctly describes the wrong flaw. There is no evidence that suggests something was indeed likely.

(E) correctly describes the wrong flaw. While an appeal to an innappropriate authority is flawed reasoning, the argument doesn't conclude that what the biologists say is true.


#officialexplanation

[ohthatpatrick]

I think you typed your question within quoted text. There's no need to quote the text, unless you're trying to highlight an excerpt. You can just type your question.

You asked ,
- How is it that conditional relationships are not causations? I thought "if" was "cause" and "then" was "effect"? Like in the sentence, "If I have money, then I will buy food" is causation, not correlation. I'm so confused. Some please help!

I don't really understand your question. They are overlapping sets. Some ideas are both causal and conditional. Some are just causal. Some are just conditional. Some are neither.

Your example of "If I have money, then I will buy food" is definitely conditional. It has an "if, then" structure, which provides the certainty we need to call something conditional.

I wouldn't personally call that causal. Having money is what causes you to buy food? It sounds like it ALLOWS you to by food, but it's the CAUSE of your buying food?

A conditional that was more like, "If I jump off this skyscraper, I will die." That is, of course, conditional. It sounds causal to me because it makes some common sense to think that jumping off the skyscraper CAUSED the death.

I think you're getting yourself confused by the fact that sometimes people like to represent the flow of causality with an arrow. If there is a chain of causality presented, it's sometimes very useful to show it to our brains that way.

But nothing is conditional unless it has 100% certainty, and many causal claims do not provide that threshold of certainty.

Hope this helps.

[andrewgong01]

I see the conditional logic flaw now because it assumed the premiuse said "Evolved Once - -> Closely RelateD" hence when it was not closely related it did not evolve once"

However, when I did this problem I thought the larger flaw was that this argument was assuming that these fishes are closely related to begin with (on Line 5) because it sounded like the argument stated that both fishes share a rare characteristics and hence it is expected that they are closely related. Then the argument goes on to argue along the lines of being related to the other fishes. My main objection was What if these fishes are never related anyways and hence we can have no way about knowing how many times algae scraping evolved - it ay have been once or it may have been innate from Day 1; I thought Choice D was a good match for this line of reasoning since we expect it is likely they are related and then we assumed they are related.

[ohthatpatrick]

I'm only saying this because I know how good you generally are at LSAT, but you seem way off on this one.


However, when I did this problem I thought the larger flaw was that this argument was assuming that these fishes are closely related to begin with (on Line 5) because it sounded like the argument stated that both fishes share a rare characteristics and hence it is expected that they are closely related.

"Some biologists" expect them to be closely related. Our author hasn't taken a position (and you know that in 99.5% of cases the author will end up DISAGREEING with 'some biologists').

And, true to form, we get our "but/yet/however" pivot, and our author definitely disagrees with them. Genetic tests show that the fish are NOT closely related.

When the author gives us the conditional rule of "If they are closely related, evolved only once", she isn't accepting the trigger as a true statement.

When you're evaluating (D), which has the form of "INFERS merely because ______ THAT ______", you're supposed to be matching the first blank with an author's premise and the second blank with a author's conclusion/assumption.

You were trying to do that with
"expected to be closely related" = "closely related is likely to occur"

And then you were thinking the author assumes that they ARE closely related, when in fact the author specifically rules out that possibility by telling us about genetic tests.

The author's conclusion is that "scraping evolved more than once", so (D) is saying
"the author infers merely because it is likely that scraping evolved more than once that scraping did, indeed, evolve more than once."

We don't have any premise that says "Scraping is LIKELY to have occurred more than once", so this answer can't be matched to the author's argument.