LSAT 108 | Section 2 | Logical Reasoning: Q5

LR Question 5 Explanation

QUESTION TEXT: Smith’s new grazing land consists entirely …

QUESTION TYPE: Necessary Assumption

CONCLUSION: Smith’s cows will probably only learn to graze on the fungus-free grass.

REASONING: Half of the fescue contains a fungus that makes cows sick. Cows avoid eating grass if they can sense a substance that made them sick before.

ANALYSIS: The argument says cows avoid substances that made them sick if they can sense those substances.

But nowhere are we told that the cows can actually detect the fungus.

Without that, the conclusion falls apart.

It might not be immediately obvious. But imagine we’re talking about food poisoning. I say: People avoid foods that made them sick, if they can identify the food. So, people will avoid a certain food.

You have to assume that they can actually recognize which food made them sick. If you got food poisoning but had no idea whether it was the chicken, rice, or salad, you couldn’t reliably avoid the culprit.

It’s the same thing here.

___________

1. Another fungus in the fungus-free grass is irrelevant. The argument only cares whether cows can avoid the illness-causing fungus.
2. CORRECT. If no cows that got sick could sense the fungus, then they can’t distinguish between safe and dangerous grass. In that case, there’s no reason to think they’ll learn to graze exclusively on the safe grass.
   Negation: No cows that have gotten sick from the fungus are capable of sensing the fungus in grass.
3. The fungus could exist in other grasses too. That doesn’t affect whether the cows can avoid it on Smith’s land.
4. Whether other animals get sick is irrelevant. The conclusion is only about Smith’s cows.
5. Whether the fungus can be eradicated has nothing to do with whether the cows can learn to avoid it.