LSAT 109 | Section 3 | Logical Reasoning: Q20

LR Question 20 Explanation

QUESTION TEXT: Galanin is a protein found in the brain. In an…

QUESTION TYPE: Strengthen

CONCLUSION: Galinin makes rats want to eat fatty foods.

REASONING: Rats that choose to eat fatty foods have more galinin.

ANALYSIS: This is a terrible argument. It’s possible, but there are other explanations:

1. Eating fatty foods increases the level of galinin.
2. Some other third factor increases the level of galinin and increases the desire to eat fatty foods.

We can strengthen the argument by eliminating one of those explanations.

___________

1. That doesn’t help. It just means that rats might sometimes eat lean foods even if they generally eat fatty food.
2. It doesn’t matter if the brains contain fat. We’re talking about how much galinin (a protein) their brains contain and whether galinin makes rats eat fat.
3. This is pretty vague. It’s quite possible, based on this, that fatty foods have 1000x the levels of galinin components than lean foods do.
4. CORRECT. This shows that galinin (the cause) existed before the rats ate fatty food (the effect). It rules out the possibility that it eating fatty foods caused the increase in galinin. 
5. This could explain why those rats eat so much fat: they metabolize it less efficiently and so they need more. But it doesn’t tell us if galinin is an effect or a cause of eating so much fat.