Critical Reasoning

Citing the frequency with which gum disease and heart disease occur in the same patients, many dentists believe that periodontal disease is a cause of a variety of cardiovascular problems, including Coronary Artery Disease.

Which of the following, if true, would most weaken the claim that periodontal disease is a cause of Coronary Artery disease?
Choices

A
Bacteria present in infected gums can become mobile and enter the bloodstream, causing arterial plaque to accumulate.

B
People who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet.

C
Infected gums are more prone to bleeding, which allows bacteria to escape the mouth and irritate arteries.

D
People who experience loss of teeth due to periodontal disease usually cut back on many foods that are harder to chew, such as lean meats and vegetables, and increase their consumption of processed foods like pudding and ice cream.

E
Patients with no history of heart disease are much less likely to have periodontal disease than patients who have had a cardiac transplant.

IMO E

But this was the answer: OA B

hey.. that was a very good question. The only reason I can think of is this.

A,C,D all support the argument.

E - also supports by establishing a connection between peridontal and heart disease. Though the statement takes time to comprehend, it can be eliminated.

B - though not the best reason, is the only one among the options that states that there is no correlation between the 2 diseases.

What is the source??

vindooo wrote:Citing the frequency with which gum disease and heart disease occur in the same patients, many dentists believe that periodontal disease is a cause of a variety of cardiovascular problems, including Coronary Artery Disease.

Which of the following, if true, would most weaken the claim that periodontal disease is a cause of Coronary Artery disease?
Choices

A
Bacteria present in infected gums can become mobile and enter the bloodstream, causing arterial plaque to accumulate.

B
People who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet.

C
Infected gums are more prone to bleeding, which allows bacteria to escape the mouth and irritate arteries.

D
People who experience loss of teeth due to periodontal disease usually cut back on many foods that are harder to chew, such as lean meats and vegetables, and increase their consumption of processed foods like pudding and ice cream.

E
Patients with no history of heart disease are much less likely to have periodontal disease than patients who have had a cardiac transplant.

IMO E

But this was the answer: OA B

seshadrivyas wrote:hey.. that was a very good question. The only reason I can think of is this.

A,C,D all support the argument.

E - also supports by establishing a connection between peridontal and heart disease. Though the statement takes time to comprehend, it can be eliminated.

B - though not the best reason, is the only one among the options that states that there is no correlation between the 2 diseases.

But E states the contrary of the cause and effect. Since the original statement says peridontal is the reason for heart disease while E says Heart disease leads to peridontal. That is the reason I went for E.

B is the only answer that weakens.

Let us see the cause and effect relation.

periodontal disease -> heart disease.

i.e. X => Y.

We also know that the above causation can be rewrititen as if not Y then not X.
E states just that.
no history of heart disease i.e., not Y , are less likely to have periodonatal disease, i.e., not X.

But by the above equation if we consider B,
it states that not X ( floss regularly, hence less chances of gum disease) => not Y (healthy diet, hence less chances of heart disease).

Thus B weakens the argument.

Great question, everyone! This one brings up a pretty important point about Weaken questions - the correct answer is often an alternative explanation for why the premises may be true while the conclusion is not.

An effective thought process on these is to look for the gap in logic while you read the premises. Here, we know that:

-Gum disease and heart disease tend to happen to the same patients (they're correlated)

-The conclusion is that gum disease causes heart disease.

Well, the gap in logic is a fairly common one - correlation does not always mean causation!

There are two somewhat standard responses to this logical flaw (X and Y are correlated, but X does not necessarily cause Y)

1) Y actually causes X (in this case, it could be that heart problems decrease blood flow to the jaw, causing gum deterioration from the inside...that would mean that heart problems actually cause gum disease)

2) X and Y are correlated because of some extra factor (as choice B says, they're correlated because the kind of person who takes care of themselves will avoid both problems, while the type of person who doesn't is vulnerable to both).

Choice B provides an alternative explanation for why the two diseases are correlated, and so it is correct.


Choice E is actually pretty consistent with the conclusion - it says that, in addition to the premise that heart and gum disease tend to occur together, the lack of these diseases is also correlated (if you don't have heart disease, it's likely that you don't have gum disease). It certainly doesn't prove the conclusion, but you could argue that it strengthens it...

I still feel it should be E and not B. E reverses the relation.

I know Brian has already replied above, request others to provide their views.

Thanks.

IMO: B

Thanks Brian. However I also have a small query as to validity of B.

In Option B we have to necessarily assume that exercise and eat a healthy diet necessarily reduces the heart disease. It might be possible that reduced heart disease may be only caused by heredity reasons.

Option E seems better.

1) Y actually causes X (in this case, it could be that heart problems decrease blood flow to the jaw, causing gum deterioration from the inside...that would mean that heart problems actually cause gum disease)

Brian, E actually follows the structure above.

Patients with no history of heart disease are much less likely to have periodontal disease than patients who have had a cardiac transplant. MEANS
Patients with history of heart disease are much more likely to have periodontal disease than patients who have had a cardiac transplant. and this means that HEART DISEASE is causing PERIODONTAL DISEASE and not other way round

B is trying to say that although occurrence of both is co-related, they are not dependent on each other BUT assumes the relation b/w diseases & exercise and healthy diet

Brian@VeritasPrep wrote:Great question, everyone! This one brings up a pretty important point about Weaken questions - the correct answer is often an alternative explanation for why the premises may be true while the conclusion is not.

An effective thought process on these is to look for the gap in logic while you read the premises. Here, we know that:

-Gum disease and heart disease tend to happen to the same patients (they're correlated)

-The conclusion is that gum disease causes heart disease.

Well, the gap in logic is a fairly common one - correlation does not always mean causation!

There are two somewhat standard responses to this logical flaw (X and Y are correlated, but X does not necessarily cause Y)

1) Y actually causes X (in this case, it could be that heart problems decrease blood flow to the jaw, causing gum deterioration from the inside...that would mean that heart problems actually cause gum disease)

2) X and Y are correlated because of some extra factor (as choice B says, they're correlated because the kind of person who takes care of themselves will avoid both problems, while the type of person who doesn't is vulnerable to both).

Choice B provides an alternative explanation for why the two diseases are correlated, and so it is correct.


Choice E is actually pretty consistent with the conclusion - it says that, in addition to the premise that heart and gum disease tend to occur together, the lack of these diseases is also correlated (if you don't have heart disease, it's likely that you don't have gum disease). It certainly doesn't prove the conclusion, but you could argue that it strengthens it...

Hi Brain,

Choice B says that the people who brush and floss their teeth regularly are also more likely to exercise and eat a healthy diet. If this has to be the correct answer then wont we have to ASSUME that people who exercise and eat a healthy diet will not have cardiovascular problems

Is it ok to make such assumptions

Again Option E states that cardiovascular problems increases the probability of dental problems. So this option looks to be a step ahead of correlation. IT probably shows causation

Please help

Regards,
Vishal