Critical Reasoning

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.


Experts, Please help me to understand this question.

The conclusion here is that engaging in social interaction will lead to improved mental abilities in the elderly. So we have a causal relationship that can be boiled down in a simple arrow diagram

social interaction ---> better mental abilities

The issue is that all we know for sure is that there is a correlation between social interaction and improved mental abilities, not necessarily a causal relationship. So while the argument asserts that some elderly people have better mental abilities because they frequently socialize, it's also possible that only the elderly people who have retained their mental abilities are able to socialize. Put another way, it's possible that the arrow diagram runs the other way

better mental abilities ---> social interaction

In this case, there isn't necessarily a cognitive benefit from social interaction, but rather, social interaction is a result of having maintained a certain minimum level of cognitive function.

Now look at answer choice B. Many medical conditions and treatments that adversely affect a person's
mental sharpness also tend to increase that person's social isolation.

If those who have experienced cognitive decline remain isolated, it doesn't mean that socialization has cognitive benefits. It means that those who have lost their cognitive abilities are no longer likely to socialize. Because B weakens the idea that socialization confers mental benefits, this is the answer.