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# Sylvia: Some psychologists attribute complex reasoning to

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Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 07:52
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Sylvia: Some psychologists attribute complex reasoning to reptiles, claiming that simple stimulus-response explanations of some reptiles behaviours, such as food gathering, cannot account for the complexity of such behaviour. But since experiments show that reptiles are incapable of making major alterations in their behaviour, for example, when faced with significant environment, these animals must be incapable of complex reasoning:

Which of the following is an assumption reqired by Slyvia's argument?

A. Animals could make major changes in their behaviour only if they were capable of complex reasoning
B. Simple stimulus-response explanations can in principle account for all reptile behaviours
C. Reptile behaviour appears more complex in the field than lab experiments reveal it to be
D. If reptiles were capable of complex reasoning, they would sometimes be able to make major changes in their behaviour
E. Complex reasoning and responses to stimuli cannot both contribute to the same behaviour
[Reveal] Spoiler: OA

Last edited by JarvisR on 26 Jul 2016, 00:59, edited 1 time in total.
Formatted the Q

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 08:00
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i go with D...

whts the OA?

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 11:07
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what not A?

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 11:12
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I like A because it is more general and wishy-washy than D.

GMAT prefers a safe wishy-washy assumption for CR.

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 21:42
I think it should be A

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 22:16
A

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 22:24
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If reptiles were capable of complex reasoning, they would sometimes be able to make major changes in their behaviour. As they are not doing that therefore they are unable to make complex reasoning.

(D)

A is more like an extreme generalization about animal reasoning with an "if only" condition.
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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 22:41
Swagatalakshmi wrote:
If reptiles were capable of complex reasoning, they would sometimes be able to make major changes in their behaviour. As they are not doing that therefore they are unable to make complex reasoning.

(D)

A is more like an extreme generalization about animal reasoning with an "if only" condition.

OK, fair point, but here is an explanation.

"since experiments show that reptiles are
incapable of making major alterations in their behaviour, for example, when faced with significant environment, these animals must be incapable of complex reasoning"

For the conclusion to be true, an animal that makes major alteration must be capable of complex reasoning. In other words, the ability to make major alteration should be determined only by the animal's complex reasoning ability and not any other ability.

If this is not true, then the conclusion falls apart because the inability to make major alteration can indicate another inability, not necesarily the lack of complex reasoning.

So, without A, the argument cannot stand. Hence A is the assumption.

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 23:30
A

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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09 Dec 2006, 23:43
I agree with 'A' too.. I don't find A to be extreme...

D is just repeating what is said in the argument already in a negated fashion...

Argument: "But since experiments show that reptiles are incapable of making major alterations in their behaviour, for example, when faced with significant environment, these animals must be incapable of complex reasoning"

D. If reptiles were capable of complex reasoning, they would
sometimes be able to make major changes in their behavior

Assumption needs to be more generic to be able to applied to any other statement..

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 08:56
Good discussion! I thought it was A too..

The OA however is D

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 09:02
gk3.14 wrote:
Good discussion! I thought it was A too..

The OA however is D

What's the OE?

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 09:10
This is what the OE says (which i disagree with)

If A were correct, it would force Sylvia in to a contradictory position. Sylvia states that reptiles engage in complex behaviour but are incapable of complex reasoning, directly contradicting Choice A.

The crux of the argument, in my opinion, is not that reptiles have complex behaviour but that they are unable to change it..

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 10:59
Let's argue a little more on this. This is my reasoning why D should be the answer.

A. Animals could make major changes in their behavior only if they
were capable of complex reasoning

This can be translated to : â€œP ONLY if Qâ€
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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 14:03
good argument swagatalakshmi..

I think where i differ is that I believe we are looking for a sufficient condition rather than a necessary one.

The argument implies that changes in behaviour is a sufficient condition to assume complex reasoning

In D: If complex reasoning-> sometimes be able to make major changes which means even if an animal does not make behavioural changes it could still have complex reasoning

To strenghten Sylvia's argument A seems the better bet

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 22:28
Quote:
since experiments show that reptiles are
incapable of making major alterations in their behaviour, for example, when faced with significant environment, these animals must be incapable of complex reasoning

Symbolize this sentence we get: Not M (Major Alterations) => Not C(Complex reasoning)

We know that not M => Not C is equivalent to C=>M
Translate this back we get: C (Complex reasoning) => M (Major alterations). In other words, "if animals are capable of complex reasoning, they would show major alterations (at least sometimes)."

A is wrong because M (Major Alterations) only if C (Complex reasoning) means M=>C, which is different from M if C or C=>M.

This is an excellent question. If you have some doubts about this question, I suggest you review the sticky thread "If X then Y, help on CR".
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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 22:38
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For example, "He hasn't taken his GMAT yet, it must be true that he isn't in a Bschool."

It would be equivalent to say "if he is in a Bschool he must have taken the GMAT".

Choice A would be equivalent to say "He has taken his GMAT only if he is in a Bschool". Which clearly may not be right because he may have taken GMAT and still not be in a bschool yet.
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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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10 Dec 2006, 22:55
Thanks HongHu

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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24 Oct 2008, 11:45
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gk3.14 wrote:
Sylvia: Some psychologists attribute complex reasoning to reptiles,
claiming that simple stimulus-response explanations of some reptiles
behaviours, such as food gathering, cannot account for the complexity
of such behaviour. But since experiments show that reptiles are
incapable of making major alterations in their behaviour, for example, when faced with significant environment, these animals must be incapable of complex reasoning:

Which of the following is an assumption reqired by Slyvia's
argument?

A. Animals could make major changes in their behaviour only if they
were capable of complex reasoning
B. Simple stimulus-response explanations can in principle account
for all reptile behaviours
C. Reptile behaviour appears more complex in the field than lab
experiments reveal it to be
D. If reptiles were capable of complex reasoning, they would
sometimes be able to make major changes in their behaviour
E. Complex reasoning and responses to stimuli cannot both
contribute to the same behaviour

The ans is D. Here is why:

Concl: Reptiles must be incapable of Complex Reasoning
WHY?
Evidance: because reptile can't make Major Changes

So Sylvia assumes that to have Complex Reasoning reptile needs to be able to make Major Changes first.

this is a question of necessity: we ought to have X and then Y can happen.
in our case the necessity is the ability for Major Changes if we have that in place Complex Reasoning is possible.

What does A tell us? a complete opposite - we need CR to have MC!
if Complex Reasoning present => Major Changes are possible

What does D tell us?
if CR were possible reptiles would have to be able (i.e. need to) perform Major Changes (first).

OR

would have to be able (i.e. need to) perform Major Changes => CR is possible

Thus the ans is D

Last edited by snaps on 03 Nov 2008, 21:02, edited 1 time in total.

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Re: Sylvia: Some psychologists attribute complex reasoning to [#permalink]

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26 Oct 2008, 13:32
(This is my first post. I teach LSAT, GMAT and GRE prep at Kaplan, and one of my students told me about GMATClub.)

Honghu's analysis is correct. This kind of question appears more often on the LSAT than the GMAT; it uses the formal logic concepts which Honghu explains.

The evidence is that reptiles are unable to make major alterations in their behaviour; the conclusion is that they are not capable of complex reasoning. As most posters have recognized, this reasoning assumes that IF an animal can't make major alterations in its behaviour, THEN it is not capable of complex reasoning.

This assumption is an "If X, then Y" statement, and so the principles of formal logic apply. Most importantly, knowing that "If X, then Y" absolutely does NOT prove "If NOT X, then NOT Y". And equally, knowing that "If NOT X, then NOT Y" does NOT prove "If X, then Y".

In this particular case, the assumption is what we just said: IF an animal canNOT make major alterations in its behaviour, THEN it is NOT capable of complex reasoning. The critical thing to understand is that this "if-then" statement does not tell us ANYTHING about what is true if an animal CAN make major alterations in its behaviour. If that is true, this statement does NOT tell us whether or not it is capable of complex reasoning. It might be, or it might not be: The statement simply doesn't give us any information about that situation.

Another way of describing what the assumption says is this: NOT being able to make major alterations in behaviour is SUFFICIENT to show that the animal is NOT capable of complex reasoning. But it is not NECESSARY: an animal could be NOT capable of complex reasoning while still being ABLE to make major alterations in behaviour.

That should explain why we the assumption "If it canNOT X, then it is NOT Y" absolutely does NOT mean "If it CAN X, then it IS Y". Equating these two statements is the oldest logical error known to civilization; the Romans called it the "pons asinorum". The GMAT uses it sometimes, and the LSAT uses it over and over and over again.

What CAN be equated to an "if-then" statement is the contrapositive of that statement:

Statement: If X, then Y
Contrapositive: If NOT Y, then NOT X

As Honghu says, "We know that not M => Not C is equivalent to C=>M." That's the contrapositive. To say the same thing a little more slowly: The assumption is "If it canNOT X, then it is NOT Y". The equivalent to this statement is "If it IS Y, then it CAN X" -- NOT, repeat not, "If it can X, then it is Y".

So the correct answer choice must say either "If it cannot X, then it is not Y" (the original assumption) or "If it is Y, then it can X" (the contrapositive, which is equivalent). Answer choice D provides the contrapositive, so it is correct.

Why is A wrong? Because of one word. At first glance, it SEEMS to say the same thing as D: If reptiles were capable of complex reasoning, then they could make changes in their behaviour. In reality, it does not say this at all. Why? Because instead of "if", the sentence contains "only if". For the purposes of logical reasoning, the phrase "only if" does NOT mean "if"; it actually means "then". So A actually says that if an animal can make alterations in its behaviour, THEN it must be capable of complex reasoning -- which is exactly what we canNOT conclude from the original assumption
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Re: Sylvia: Some psychologists attribute complex reasoning to   [#permalink] 26 Oct 2008, 13:32

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