Logical reasoning PrepTest 117 · Section 2 · Question 5

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
Musicians have larger CC than nonmusicians, so musical training must cause anatomical changes to the brain.

Answer Anticipation:
The conclusion here is about as clearly causal as they come—it includes the word causes" in it! Whenever that happens, we should look to see if there's a correlation/causation flaw.

Here, the causal conclusion is reliant on a correlation between the size of a part of the brain (just call it CC, no need to try to speak Latin!) and musical training.

When an argument makes a correlation/causation jump, it's assuming that correlation does equal causation. Another way of saying that is that it assumes all of the reasons correlation doesn't equal causation don't apply in the given case.

In yet other, more specific words, the argument is assuming:
(1) There's no alternative cause that results in someone's CC growing and in them being more likely to take on musical training
(2) The correlation isn't merely a coincidence
(3) It's not the larger CC that gets people interested in music

Any answer that addresses these assumptions could be correct, so we need to stay flexible!

Answer Explanation:
This answer is required for the argument to work. It's related to reversed causality—if the larger CC came first, then it can't be the effect and is more likely the cause (if a causal relationship exists).

Key Takeaway:
Flaws generally represent shortcomings in arguments—things the argument assumes are true without establishing. The common errors in reasoning have common shortcomings. For a Strengthen with Necessary Premise question, the argument is assuming that those shortcomings aren't present, and using that framework can help you to anticipate an answer in this question type.

Incorrect. The argument concludes that musical training causes changes to the brain. While it notes this is particularly true" when the training starts at a young age, the relationship is stated as a generalization. So it not having the effect later in life would actually undermine the argument.

Incorrect. The argument talks about increasing the size of the CC, and the average size being larger. That's population—wide, so the argument doesn't rely on any two particular people who have trained about the same having the same sized CC—just that they would, on average, have a larger CC than people without musical training.

Incorrect. This answer is too extreme. The argument speaks about the average" size of the CC, so if a few non—musicians with the largest CC have larger CCs than musicians with the smallest CC, then the argument can still hold.

Incorrect. This answer similarly fails because the argument talks in averages. The argument doesn't need the nonmusicians to have skipped any activity that could stimulate growth of the CC—they just needed not to engage in activities that had as stimulating an effect for as long.