Logical reasoning PrepTest 155 · Section 1 · Question 5

This answer choice weakens the argument by showing that G., which also has toothless beaks and weak jaw muscles, may not have have fed by filtering food from mud and water.

While interesting, this fact doesn't strengthen or weaken the argument. Even if toothless beaks and weak jaw muscles are exclusive to ornithomimids like G., that doesn't mean that G. fed by filtering food from mud and water.

This answer choice does the precise opposite of what we're looking for. We're looking for an answer choice that shows that G. and ducks/geese possess relevant similarities beyond the comblike plates. Knowing they lived in the same habitat or had similar digestive systems would provide additional evidence that they fed the same way. This answer choice shows that they didn't have any other relevant similarities weakens the comparison in this argument.

Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
A particular family of dinosaurs tended to have toothless beaks and weak jaw muscles. One species of that family ... the ... Gallimimmumu — you know what, let's just call it G. — also had a "comblike plate" in its beak. Modern ducks and geese also have similar comblike plates, and they eat by straining food out of water and mud with their beaks. So G. probably got its food the same way, paleontologists hypothesize.

Strategy Overview:

1. Argument or facts? Always argument, so identify premises and conclusions of argument
2. Anticipate why the premises are not enough to show that the conclusion is true
   1. Causal argument? Look for answer choice that:
      1. Rules out possible alternate cause
      2. Shows same cause, same effect
      3. Shows no cause, no effect
      4. Shows the cause and effect are not reversed
3. If not causal argument, anticipate ways to fix problem with argument
4. Use anticipations to select the answer choice that, if true, would strengthen argument

Answer Anticipation:
On Strengthen questions, the correct answer usually helps fix a flaw in the argument. This is why experienced LSATers try to identify the problems with the argument first. Once they identify the problem, they're better prepared to find the answer choice that fixes that problem and strengthens the argument.

This particular argument doesn't seem to be causal, so we should look for a different problem. The first thing we should note is that this argument rests on a comparison. Just because ducks and G. have a similar physical feature doesn't necessarily mean they used it in the same way. To assume otherwise would make these scientists a bunch of ... quacks ... (sorry). To fix this problem, it would help the argument if we could show that the ducks and G. shared other similarities, such as a similar habitat, digestive system, etc. Really, any shred of evidence that would support the idea that these particular dinosaurs fed by filtering snacks out of mud and water.

Answer Choice Explanation:
Some test-takers may erroneously skip over this answer choice because it doesn't mention ducks and geese. However, this does strengthen the argument's conclusion. First, we know from the passage (and kindergarten) that modern ducks and geese also feed in wet environments, so this answer choice strengthens the comparison between G. and modern ducks/geese. And, perhaps more to the point, if G. lived in wet environments, it's more likely they'd have needed to sift through water and mud for their food. Imagine the opposite answer choice. Suppose we found all the G. fossils in regions that were bone-dry during G.'s lifetime. That would completely refute this argument's conclusion. So this answer choice provides exactly what we need: new information that makes the conclusion stronger

Key Takeaway:
Comparison flaws are among the most common flaws on Strengthen questions. Many arguments conclude that two entities must share a particular attribute because they share some other attribute. And we generally want to strengthen arguments that commit such a comparison flaw by showing the two entities are relevantly similar in other ways. This particular question shows that the correct answer doesn't need to bring up one side of the comparison to strengthen that comparison. The correct answer choice here didn't mention ducks and geese. But that's fine, because we knew from the passage that modern ducks and geese also feed in wet environments. So, the correct answer provided a relevant similarity between ducks/geese and the G. dinosaur.

We aren't interested in other dinosaurs for this question. There were lots of dinosaurs! The paleontologists made a hypothesis about just one dinosaur. So the only thing we care about is whether that dinosaur fed in the way paleontologists hypothesize it did.