#26 - The three-spine stickleback is a small fish that lives

[nicizle]

I'm having trouble making sense of this question. Out of all the questions I've done, this is probably a contender for the worst.

I would've noted the causal relationship in the conclusion as follows: if armor limits speed of stickleback's growth --> size is a better defense. Or, in other words, if no armor --> then size is better defense. I'm confused on why the explanation noted the causal relationship differently.

To weaken the conclusion, wouldn't we need to search for an answer choice that details an alternate explanation for why size is the better defense? How does B provide any kind of weakener to that point? I don't understand how lake stickleback having a larger size that enables them to survive colder winter provides an alternative explanation for why size is the better defense.

[Jeff Wren]

Hi nicizle,

This question was definitely a tricky one!

First, if you haven't already done so, I'd recommend reading Dave's explanation found here:

viewtopic.php?f=1331&t=31625

Second, it's important to separate the final sentence of the stimulus into two parts, the first half is actually a premise and the second half is the conclusion. This is a common sentence construction used on the LSAT (Since A, therefore B), so you'll want to be familiar with it.

Here, the fact that armor limits the speed of the stickleback's growth (combined with the fact that the lake stickleback do not have armor) indicates that a larger size is a better defense than armor against the lake stickleback's predators according to the conclusion.

This conclusion is providing the reason (or cause) for why the lake sticklebacks do not have armor.

Often the hardest part of solving questions with causal reasoning is correctly identifying it when it appears because the arguments don't always use the words "cause" or "effect." Usually, something happens, such as an odd phenomenon (the effect), and then someone gives a reason for how/why that thing happened (the cause).

Here, the odd phenomenon (effect) is that lake stickleback don't have armor, which would seem to be a helpful thing to have in general. By explaining that armor inhibits growth and then concluding that larger size must be a better defense for these fish than armor, the argument provides a cause for this effect.

With the correct cause/effect identified, this question becomes considerably easier, especially if you're able to recognize that Answer B is providing an alternate cause for the effect, which is one of the best ways to weaken a causal argument.