It is widely assumed that people need to engage in intellectual activi

It is widely assumed that people need to engage in intellectual activities such as solving crossword puzzles or mathematics problems in order to maintain mental sharpness as they age. In fact, however, simply talking to other people---that is, participating in social interaction, which engages many mental and perceptual skills---suffices. Evidence to this effect comes from a study showing that the more social contact people report, the better their mental skills.

Which of the following, if true, most seriously weakens the force of the evidence cited?

(A) As people grow older, they are often advised to keep exercising their physical and mental capacities in order to maintain or improve them.

(B) Many medical conditions and treatments that adversely affect a person's mental sharpness also tend to increase that person's social isolation.

(C) Many people are proficient both in social interactions and in solving mathematical problems.

(D) The study did not itself collect data but analyzed data bearing on the issue from prior studies.

(E) The tasks evaluating mental sharpness for which data were compiled by the study were more akin to mathematics problems than to conversation.


Type: Weaken
Boil It Down: Social interaction up -> Boost mental skills
Missing Information: There aren’t other factors
Goal: Find the option that shows that there could be another factor in play (de-link social interaction as a mental skills booster)
Analysis: This prompt sets up a classic causal argument (Social interaction up -> Boost mental skills). That means the reasoning assumes that there aren’t other factors in play. To weaken we need to select an option that either clouds the connection between social interaction and mental skills, or points to another factor altogether.

A) What happens as people grow older is an entirely separate subject. This question deals with a group of people in general, so zeroing in on a random sub-set, a specific niche within the overall group about what those people can do to stay sharp as they grow old is irrelevant. It’s Out Of Focus.

B) Yes. Here we’re presented with an entirely separate cause as to the correlation between social interaction and a boost in mental skills. If someone is suffering from a medical condition that impacts mental sharpness and that if the illness impacts the willingness to socialize, of course that would artificially boost the correlation between social interaction – and mental sharpness. It’s not fair to say that being more social is the cause of possessing greater mental skills then. This option brutalizes the reasoning in the argument.

C) If some people are strong at both, that could appears to be aligned with the argument that we’re asked to weaken since it shows the presence of both the cause and effect. However, it’s just not clear entirely clear how C either strengthens or weakens.

D) It’s not at all clear how analyzing data vs gathering and analyzing data from prior studies would weaken or strengthen. By itself, this option does nothing. Flawed data is a sucker choice on the GMAT. The GMAT doesn’t question the integrity of data. It questions the integrity of the reasoning interpreting the data.

E) This option attacks the wrong end of the causal relationship. We need an option that points to an alternative cause of a boost in mental skills (as in we need an option that shows that it’s not social interaction that boosts mental skills). This option just attempts to redefine how mental skill is defined by the study, and the option in NO way addresses the cause of the heightened mental skills. Instead, if this option had attacked the cause rather than the effect, then it would weaken too. For example, if it said: “The tasks defining social interaction compiled by the study were more akin to mathematics problems than to social interaction” then this option would then reveal that there is a totally different cause other than social interaction.


Additional Analysis About Option B)
The key to understanding why option B weakens the argument requires paraphrasing the conclusion, and taking that paraphrase an extra step (and that’s the core reason why this question is up there on the difficulty spectrum):

The argument is essentially saying that social interaction boosts mental sharpness.

Paraphrased conclusion
That claim could be paraphrased to say: without social interaction, mental sharpness would be reduced.

Now read B):
Many medical conditions and treatments that adversely affect a person's mental sharpness also tend to increase that person's social isolation.

And since B) has a classic GMAT style double-negative, let's paraphrase B) too:
Many medical conditions and treatments that reduce mental sharpness also tend to reduce social interaction.

That means B) is saying:
Medical Conditions and Treatments ➧ Mental Sharpness ⬇, Social Interaction ⬇.

So option B is introducing this Medical Conditions and Treatments alternative cause that impacts both social interaction and mental sharpness. So it's not that social ➧ mental, they go hand in hand attributable to another cause, thereby weakening the argument.

A tricky one! Definitely one of the trickiest of the new CRs in the 2016 OG, for sure.


Bigger GMAT Picture:
On tricky causal arguments, ACT/GMAC won’t just come out and say that it’s this other cause. That can be too obvious: for example, check out this low difficulty OG question with an obvious alternative cause: in-the-last-decade-there-has-been-a-significant-decrease-in-136789.html

On tougher causal questions (like this Intellectual Activities question), ACT/GMAC will try to muddle the relationships with double negatives, or reversing the causality altogether.
For example: The food truck must have been successful because now they have a restaurant. Weakener: Well actually, the restaurant came first, and then they started operating the food truck.

So, if you're consistently scoring in the Verbal 40+ range, expect the causal arguments you see to involve that extra layer.