Expert: What criteria distinguish addictive substances from nonaddicti

Question

Expert: What criteria distinguish addictive substances from nonaddictive ones? Some have suggested that any substance that at least some habitual users can cease to use is nonaddictive. However, if this is taken to be the sole criterion of non addictiveness, some substances that most medical experts classify as prime examples of addictive substances would be properly deemed nonaddictive. Any adequate set of criteria for determining a substance’s addictiveness must embody the view, held by these medical experts, that a substance is addictive only if withdrawal from its habitual use causes most users extreme psychological and physiological difficulty.

Which one of the following can be properly inferred from the expert’s statements?

(A) If a person experiences extreme psychological and physiological difficulty in ceasing to use a substance habitually, that substance is addictive.

(B) Fewer substances would be deemed addictive than are deemed so at present if an adequate definition of “addictive” were employed.

(C) A substance that some habitual users can cease to use with little or no psychological or physiological difficulty is addictive only if that is not true for most habitual users.

(D) A chemical substance habitually used by a person throughout life without significant psychological or physiological difficulty is nonaddictive.

(E) “Addiction” is a term that is impossible to define with precision.

nahid78 · Answer

Took me almost 4 minutes. What's the source of this question.

aurobindomahanty · Answer

The question is from old LSAT papers.

CrackverbalGMAT · Answer

some people's view point --

Any substance that at least some habitual users can cease to use is nonaddictive.

If this viewpoint is followed, some substances, classified as addictive by medical experts, might be classified as non addictive.

Medical experts + author's viewpoint --

Substance is addictive --> Withdrawal from its habitual use causes  most  users extreme psychological and physiological difficulty  ------(1)

(Note that "only if" implies a necessary condition; just "if", on the other hand, implies a sufficient condition).

Let us take a look at the answer options --

Option A - Incorrect

A person experiences extreme psychological and physiological difficulty in ceasing to use a substance habitually --> substance is addictive

Note that this reverses condition#1 stated above. Also, this talks about "all users" whereas condition #1 talks about "most users".

Option B - Incorrect

We do not know what definition of "addictive" is employed currently. 
However, if the definition proposed by medical experts (=adequate set of criteria) is employed over the one proposed by some people, then   more   substances would be classified as addictive.

Option C - Correct answer

Some habitual users can cease to use the substance with little or no psychological or physiological difficulty -- this condition SHOULD NOT BE TRUE FOR MOST HABITUAL USERS.

the actual condition then is --

Substance is addictive --> MOST habitual users CANNOT cease to use the substance with little or no psychological or physiological difficulty  (Note that this is the necessary condition as indicated by "only if").

Option D - Incorrect

this option does not talk about "withdrawal from habitual use". Not relevant.

Option E - Incorrect

The author has never said that "addiction" is impossible to define with precision. Incorrect.

Mo2men · Answer

Dear CrackVerbal,

I can't see how there is reverse in logic in Choice A. Rather, I see that quote same sentence.

From prompt: only if withdrawal from its habitual use causes most users extreme psychological and physiological difficulty, then substance is addictive.

Choice A: If a person experiences extreme psychological and physiological difficulty in ceasing to use a substance habitually, then substance is addictive.

What is understand about reverse logic is the following:

If the substance is addictive, then withdrawal from its habitual use causes most users extreme psychological and physiological difficulty. This is not the case for choice A.

I see that choice A put it in general form 'a person' while in prompt we talk about 'most'. Also, using 'only if' for necessity and 'if' for sufficiency. Hence it is wrong.

Can you elaborate pls.

CrackverbalGMAT · Answer

"only if" is used for necessary conditions; "if" for sufficient conditions.

That is what I meant by "reverse".

In the original this is the necessary condition -- "withdrawal from its habitual use causes most users extreme psychological and physiological difficulty".
In option A this, however, is the sufficient condition -- "a person experiences extreme psychological and physiological difficulty in ceasing to use a substance habitually".

zac123 · Answer

i am still not convinced why A is the wrong ans . Also , are such questions useful for GMAT CR preparation ?

KarishmaB · Answer

Argument:

Some have suggested a way to classify addictive substances - any substance that at least some habitual users can cease to use is nonaddictive.
(So as per them, addictive is that substance which no habitual users can cease to use)

But then, some substances that most medical experts classify as addictive would be called nonaddictive.
So one criterion for these medical experts should be: a substance is addictive only if withdrawal from its habitual use causes most users extreme psychological and physiological difficulty

(A) If a person experiences extreme psychological and physiological difficulty in ceasing to use a substance habitually, that substance is addictive.

If MOST people experience extreme psychological and physiological difficulty in ceasing to use a substance habitually, that substance is addictive - is the author's view. There still may be a few who do not experience these difficulties. 
There may be substances that are non addictive but a few people may face difficulties in ceasing to use them. So if a person experiences extreme difficulties, can we say that that substance is addictive? Not necessary. Perhaps, most people do not experience difficulties.

(B) Fewer substances would be deemed addictive than are deemed so at present if an adequate definition of “addictive” were employed. 
An adequate definition of addictive encompasses more criteria as per the author. He is trying to widen the definition to include more substances. Hence, possibly, more substances would be deemed addictive if an "adequate definition" (as per the author) were employed.

(C) A substance that some habitual users can cease to use with little or no psychological or physiological difficulty is addictive only if that is not true for most habitual users.

Yes, this is what the argument tells us - a substance is addictive only if withdrawal from its habitual use causes most users extreme psychological and physiological difficulty.

(D) A chemical substance habitually used by a person throughout life without significant psychological or physiological difficulty is nonaddictive.

We are talking about difficulty faced when ceasing to use the substance. What happens when you continue using the substance is irrelevant to our argument.

(E) “Addiction” is a term that is impossible to define with precision.

We don't know that. The argument does seem to imply that it is not defined with precision right now. But is it impossible to define? We don't know.

Answer (C)

KarishmaB · Answer

And yes, the question is certainly fair play for GMAT.

DavidTutorexamPAL · Answer

Another issue, in addition to what @vertiaskhrishma said, is that the expert's argument only tells us that if something is an addictive substance, it will definitely cause difficulty from withdrawal. this does NOT logically mean that the opposite is necessarily true - that if something causes difficulty, it is addictive. 
Is this clear?

zac123 · Answer

yes , its clear now , thanks  DavidTutorexamPAL  and  VeritasKarishma

VerbalBot · Answer

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Expert: What criteria distinguish addictive substances from nonaddicti

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Expert: What criteria distinguish addictive substances from nonaddicti

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