Q20 - A study of rabbits in the 1940's

[ohthatpatrick]

Question Type:
Flaw

Stimulus Breakdown:
Conclusion: Mammalian chromosomes must preclude the possibility of parthenogenesis.
Evidence: There was a study that showed Parth CAN occur with mammals. But its methods were flawed and no other study has successfully demonstrated mammalian Parth, even though it's common in nonmammals.

Answer Anticipation:
The author's conclusion brings chromosomes in out of nowhere. What is it connected to? The author is assuming that mammals can't do Parth, and she's trying to figure out why. Nonmammals can do Parth, so the author thinks that mammalian chromosomes are to blame. We could find fault with this argument by finding any OTHER WAY to explain why mammals don't do parth. But -- who said mammals DON'T do Parth? The author hasn't said so, but she assumes this is the case, since the study that showed mammals CAN do parth has been torn down and never replicated. Even if the 1940 study didn't prove the existence of mammalian Parth, that doesn't allow us to infer that mammalian Parth doesn't exist. The author is overly sure of herself in thinking that "the possibility of Parth in mammals IS PRECLUDED".

Correct Answer:
A

Answer Choice Analysis:
(A) Yes! Take the claim "mammals CAN do parth". The 1940 study made this claim. The author shows us that this claim has NOT been proven to be true (flawed methods, never replicated). Then she assumes that the claim is false, i.e. "mammals CANNOT do parth". And that's how she gets to her conclusion about chromosomes, speculating some causal reason for why "mammals CAN'T do parth".

(B) Does this match the Core? Does the author conclude/assume that some characteristic is shared by all nonmammalian vertebrates? Uh … no. She provides, as a FACT, that a characteristic (parth) is shared by MANY nonmammalian vertebrates. Since the first ingredient didn't match, no need to keep reading.

(C) Does this match the Core? Does the author rule out an explanation of a phenomenon? Uh … no? She PROVIDES an explanation for the phenomenon (that she thinks exists) that mammals can't do Parth.

(D) Was there a Conditional Logic Flaw? If there were any necessary condition of Parth, it would be "reproduction without fertilizing an egg". Did the author argue that "Since this thing reproduced without fertilizing an egg, this thing did parthenogenesis"? Heavens, no.

(E) The author doesn't assume that the methods in the 1940 study were flawed; she presents it as a factual premise "shown to be flawed". We can stop reading there.

Takeaway/Pattern: Tough one! They disguised this classic "Unproven vs. Untrue" flaw by putting a specific Explanation for a Phenomenon in the conclusion. If they wrote an answer choice that said "the author fails to consider alternative explanations for why mammals can't do Parth", it would be a valid objection. But, in reality, they were testing us on whether we noticed the author making the assumption that "mammals can't do Parth". This assumption was embedded in the logic of the author's conclusion, which assumes that SOMETHING precludes Parth in mammals.

#officialexplanation

[chike_eze]

Correct = (A)
Question Type = ID Flaw

Argument:
A study of rabbits in the 1940's showed that parthenogenesis (P) occurs in mammals. But the study method has been shown to be flawed, and no other studies since then show that P occurs in mammals.

However, P is known to occur in some non-mammals, therefore something about mammals causes them (mammals) not to exhibit P behavior.

Assumption: Because no studies show that mammals exhibit P behavior conclusively means that mammals do not exhibit P behavior.

Just because something has not been proven true, does not necessarily mean that it is false.

(A) Expresses this flaw exactly!
> Just because something hasn't been proven true, doesn't make it false

B) No. part to whole flaw
C) No. Does not account for other possibilities flaw
D) No. Confuses necessary with sufficient flaw
E) No. Author does not assume methods in study were flawed. Fact: A study in 1940 was flawed, other studies were not flawed but they did not support mammals exhibiting P.

[noah]

Another strong explanation! My changes in italics:

Correct = (A)
Question Type = ID Flaw

Argument:
There must be something in mammals that prevents P from occurring. Why?

Because P has not yet been found in mammals, but it is found in nonmammals.

A study of rabbits in the 1940's showed that parthenogenesis (P) occurs in mammals. But the study method has been shown to be flawed, and no other studies since then show that P occurs in mammals.

Assumption: Because no studies show that mammals exhibit P behavior conclusively means that mammals do not exhibit P behavior.

Just because something has not been proven true, does not necessarily mean that it is false.

(A) Expresses this flaw exactly!
It can be a bit confusing that it refer to "not been proven true" - but this is referring to mammals having P.

(B) No. The argument doesn't conclude that all nonmammals have P.
(C) Is tempting! Maybe it's not because of the mammalian chromosomes...but (C) is flawed more basically - there's no explanation ruled out!
(D) No. Nobody is confusing a necessary with sufficient!
(E) No. The author does not assume methods in study were flawed. Fact: A study in 1940 was flawed. Also, the flaw is not because the finding couldn't be generalized to others mammals!

[hippo3717]

I was really tempted by C
due to the wording of the conclusion: it's so strong by saying that there must be something about...

doesn't that wording actually exclude other explanation?

[noah]

I was really tempted by C
due to the wording of the conclusion: it's so strong by saying that there must be something about...

doesn't that wording actually exclude other explanation?

Good question.

Just because one explanation must be valid doesn't mean that others aren't also in play. For example:

There must be something about Romney's position on "Obamacare" that precluded him from winning the 2012 election.

Just because that must be in play does not mean that other factors weren't as well. The author of that Romney/Obamacare argument might agree with the idea that Romney's comments about the 47% also precluded him from winning.

That clear it up?

[Aquamarine]

Oh boy..I still don't understand why C is incorrect.
I think "there is another explanation~~" can match "since parthenogenesis is~" part in the stimulus.
Why is C incorrect and A an answer?

Please someone explain me.
Thanks!

[123bis]

I'm still confused as to why B is wrong. Just because some nonmammilian vertebrate species exhibits the characteristics doesn't mean they all do. Can someone please expand ?

[vickpetrosian1]

I'm still confused as to why B is wrong. Just because some nonmammilian vertebrate species exhibits the characteristics doesn't mean they all do. Can someone please expand ?

B is wrong because that is not the main point of the argument here, it may be true that they don't all have the ability to self produce, but it specifically words that a "wide variety" are known to have this ability= meaning not ALL of them.

[tuesdayninja]

I'm still confused as to why B is wrong. Just because some nonmammilian vertebrate species exhibits the characteristics doesn't mean they all do. Can someone please expand ?

B is wrong for several reasons. Firstly, nowhere in the stimulus is it inferred that ALL nonmammalian vertebrate share a characteristic (parthenogenesis), the premise simply says parthenogenesis is known to occur in 'A WIDE VARIETY of nonmammalian vertebrates'. A wide variety of nonmammals does not equal all nonmammals.

More importantly though, B does is not relevant to the argument in the stimulus. The argument says that there is something about mammalian chromosomes that prevents parthenogenesis because the study's methods were flawed and no other studies have succeeded in demonstrating mammalian parthenogenesis. It doesn't matter whether or not ALL nonmammalian vertebrate exhibit parthenogenesis.