LSAT 114 | Section 4 | Logical Reasoning: Q22

LR Question 22 Explanation

QUESTION TEXT: In humans, ingested protein is broken down into amino…

QUESTION TYPE: Necessary Assumption

CONCLUSION: Sugar plays a role in mood elevation.

REASONING: Sugar ➞ insulin ➞ removal of all amino acids except tryptophan ➞ tryptophan enters brain ➞ serotonin

ANALYSIS: This argument plays on the common knowledge that serotonin has something to do with being in a good mood. It’s easy to forget that this argument doesn’t actually tell us anything about what serotonin does.

The argument assumes that serotonin helps elevate the mood.

___________

1. This isn’t necessary. It’s only necessary that serotonin elevates mood.
2. This is like A, and it isn’t necessary. The argument would be ok if not consuming sugar was simply neutral for mood. 
3. It doesn’t matter if there are other ways to produce serotonin. It’s only necessary that tryptophan is one way to produce serotonin.
4. CORRECT. If this isn’t true then it’s not clear why sugar would elevate mood. 
5. We don’t have a clue about this. There could be something else about protein that elevates mood, even if the amino acids in it block out tryptophan.