LSAT 16 - Section 3 - Question 01

This is a weakening question: Which one of the following, if true, most seriously weakens the argument?

The first thing we learn from the stimulus is that there is this species of spider, the painted spider, and they have stickier webs than the other spiders that share their habitat. Stickier webs are better at trapping specifically flying insects, spiders hunt for food by trapping insects, and therefore the argument concludes the spider is a more successful predator than its competitors.

The overall structure of this argument is fairly simple; there is this way in which a particular kind of spider differs from others, and since this would be helpful for preying on flying insects, we conclude that in virtue of this one factor the painted spider is a better predator than its competitors. The problem with this argument is we know very little; we know very little about other possible differences between the painted spider and other spiders, about the overlap between other spiders and the painted spiders competitors, and about what portion of the prey in this habitat are specifically flying insects. The right answer is going to introduce some information that exploits one of these gaps in the argument. Let’s eliminate the answers that fail to do so:

Answer Choice (A) This addresses the issue of what portion of the prey in the habitat are specifically the flying insects which would be susceptible to the painted spider’s stickier webs. The problem is that it gives us almost no real information; “not all” could mean one single non-flying insect or almost all of the insects. Without more information, this answer is entirely compatible with both supporting this argument (a low number of non-flying insects) or weakening it (a large number of non-flying insects), and therefore does not by itself seriously weaken the argument.

Answer Choice (B) All this answer does is tell us that certain kinds of insects would be unlikely to be trapped by non-sticky webs, and therefore gives us a reason to think the painted spider might have a real advantage over other spiders. If this were a strengthening question that might be meaningful, but for us this does the opposite of what we want.

Answer Choice (C) This is just an irrelevant fact. Whether the spider paralyzes or kills its victim doesn’t bear any clear relation to the impact of its sticky webs on its success as a predator compared to its competitors.

Correct Answer Choice (D) This provides a downside to the painted spider’s stickier webs. Even if they are more efficient at trapping insects that fly into them, if they are more visible maybe much less insects fly into them, so that the painted spider is actually a much worse predator than other spiders. At the very least, this weakens the main support for the argument’s conclusion, that the painted spider’s stickier webs give it a plain and simple advantage.

Answer Choice (E) E introduces web size to equation, and does so in a really unhelpful way. If this said that the webs were significantly smaller than other spiders and therefore caught less insects, that might help us weaken the conclusion that painted spiders are better predators, but as stated this answer does nothing for us.