I'll see what I can do on this question. It is definitely a hard one (at least, for me)
THE PROCESSThis is a weaken EXCEPT question so let's focus on the core. After finding the core, we are looking for something that won't necessarily weaken the conclusion but perhaps be out of scope or maybe even
strengthen it. A common answer to Strengthen/Weaken EXCEPT questions bear little relevance to the argument so I'll keep that in mind.
A
study showed...
Depression
correlated with
less left frontal lobe activity
+
Good-natured participants
correlated with
greater left lobe activity
→
Mood is a
result of frontal lobe
As you can see, this is a correlation/causation issue. We have two groups of people. One group, the sad group, has less frontal lobe activity. The other group, the happy group, has more frontal lobe activity. The argument thus concludes that the frontal lobe
causes mood. However, does this have to be true? Not exactly. There could be a number of reasons why this is not true and the incorrect answers (the weakeners) will probably speak to those reasons:
(1) It could actually be that MOOD causes FRONTAL LOBE ACTIVITY. In other words, it reverses the chain of causality from (FLA → M) to (M → FLA)
Furthermore, it could actually be that MOOD or FRONTAL LOBE ACTIVITY are actually caused by a THIRD thing. Maybe this is all just a big coincidence and something such as where the people live causes frontal lobe activity or perhaps mood elevation/depression. Who knows?
In addition to these, the weakeners could do the following...
What would an example of these be? For 2, an example could be that, "Another survey found multiple participants with a high level of left frontal lobe activity with clinical depression. For 3, an example could be that, "Modern scientists have discovered that depression is actually caused by eating too many Ritz crackers while being good-natured is actually the cause of playing 3+ hours a day of Super Mario Bros."
Now that we are armed with these thoughts. We can take a look at the questions. Someone may offer their own insight but I think it might be easiest to attack this weaken EXCEPT question by searching for the incorrect answers - the weakeners - first.
Just remember, the argument is saying that Frontal Lobe Activity
causes mood. Why should we doubt this?
THE ANSWER CHOICES(A) This refers to how drugs
act. In other words, it is just recounting
how the drugs do what they do. This doesn't really speak much to the idea of disposition because these drugs are altering your frontal lobe activity. I am not too sure about this one, I'll skip it and return to it later.
(B) This provides an
alternative cause by reversing the conditional logic. It basically says that depression causes excessive sleep and excessive sleep causes the suppressed left lobe activity. In other words, "Depression → Sleep → Suppressed Left Lobe Activity." What this is doing is actually flipping the argument around. It is saying, "well the LSAT thinks your brain activity causes your mood. That's not true. (B) thinks that your mood actually causes your brain activity."
***NOTE: (B) would actually have NOT been a weakener if it wasn't for the phrase that says, "a typical consequence of clinical depression." This phrase is instituting an absolutely crucial distinction by showing how depression is the root cause of the brain activity. If it would have just said, "Excessive sleep is known to suppress frontal lobe activity" that wouldn't have done much because we need to prove one of the following:
(1) That the conditional is backwards (this is what B does)
(2) That the mood was actually caused by something else
(3) That the frontal lobe activity didn't cause the mood
(C) This really just boils down to the following phrase, "general disposition is subject to variation." The front part of the sentence is probably just there to confuse you. Either way, if disposition is varied, how can we say that a study done at a particular time in a particular way does anything? This weakens!
(D) This is definitely a weakener because it shows that Frontal Lobe Activity doesn't cause Mood! Why? Because they are both caused by something else! If mood and frontal lobe activity are caused by a third thing then there is serious doubt as to if one causes the other.
(E) This provides the effect - the stimulated left lobe activity of happy people - without the cause. This weakens in the way that we discussed earlier. If we have the effect without the cause, this makes us doubt whether the cause really prompts the effect.
THE CORRECT ANSWER
As we can see, (A) is really the only one that doesn't fit this mold of three ways we can weaken a causal claim. We can select it by POE. Alternatively, we can try to understand it further...
We have already gone over the three ways to weaken a causal claim. What does answer choice do? What is its structure? It's structure is...
"Drugs → Increased Left Lobe Activity."
However, what does the argument say? It says both that...
"Increased Left Lobe Activity → Good nature"
"Decreased Left Lobe Activity → Depression."
Do these two match up? No. Therefore, this answer is really out of scope and doesn't weaken the causal connection at all. In addition, as I said before, we don't really care HOW the drugs do what they do.
Hope that helps.