- PowerScore Staff
- Posts: 8950
- Joined: Feb 02, 2011
- Wed Jun 29, 2016 9:09 am
#26722
This is a Strengthen question, where we're asked to find an answer choice that supports the journalist's argument. So let's start with the argument and see what the journalist believes.
The argument here is straightforward enough: from the observation that people with iron-rich diets are much more prone to develop Parkinson's disease than those whose diets contain less iron, the journalist concludes that limiting the consumption of food with a lot of iron (meat, seafood, etc) should reduce the chance of developing Parkinson's.
This is a causal argument--we move from the correlation of iron-rich diets and a high incidence of Parkinson's to the conclusion that iron is a cause of Parkinson's and thus limiting this cause should reduce its effect--and it seems, at least superficially, to make sense. But causal arguments on the LSAT are pretty much always dubious affairs. There's simply a lot that can go wrong when you attempt to tie two events together in an exclusive, active way, as LSAT authors do when endorsing causal relationships. This is why you see causality in so many Strengthen and Weaken questions: its suspect nature makes it ripe for manipulation.
Generally the most effective way to weaken causality (although hardly the only way) is to introduce an alternate cause. Doing so immediately disrupts the presumed relationship and crushes the author's conclusion. With Strengthen questions you very often see the opposite: you can bolster a causal claim by simply removing a potential competing cause. It's not the most powerful support in the world, but it does help: saying that an alternative cause isn't the reason for the observed effect means the author's claimed cause is more likely to be. This is a crucial idea, as it not only happens with some frequency, but it's also at the heart of some of the toughest Strengthen questions: it's just a counterintuitive notion on the surface, that removing/negating something that hasn't been discussed in the stimulus could in fact lend more credibility to the idea in question.
So how does that work here? Well, consider some alternate causes to dietary iron that could lead to a higher incidence of Parkinson's disease, and still fit with the facts as given. What if, for instance, smoking cigarettes is really the reason people get Parkinson's, and nicotine also makes you crave steak/seafood/iron-rich meals? That would clearly weaken this conclusion ("smoking has long been known as both the leading cause of Parkinson's and a trigger for iron consumption" or whatever). So how would you strengthen against that idea? Negate it: "smoking is a well-known Parkinson's contributor and smokers are notorious for diets low in iron." Seems irrelevant at first, sure, but when you think about it you've just removed a competing theory, thereby making the theory on offer more compelling.
That's a demonstration of the principle at work, of course, and not specific to the answers in this question, but hopefully it serves to show the process by which eliminating an alt. cause can, in a rather roundabout way, offer support.
What happens in the correct answer choice in #21 follows the same mechanism. In (A) we're told that people genetically prone to develop Parkinson's don't eat more iron than people without a genetic predisposition. In other words, a genetic predisposition to getting the disease--something that clearly is a cause--isn't related to the high-iron correlation noted in the stimulus, thus making iron, and not genetics, a more likely contributor. We've removed genetics from the equation and, in so doing, made iron's role more prominent. And thus the author's conclusion about iron --> Parkinson's more likely.
To test this, imagine answer choice (A) stated as its opposite: people with a genetic predisposition to Parkinson's consume MUCH more iron than those without those genes. What would that do here? It would destroy the author's view! If a genetic predisposition, something that undeniably makes you more likely to get the disease, also makes you eat more iron (or if the two are for whatever reason associated), then reducing iron is irrelevant--it's your genes, not your diet--and the conclusion can be dismissed. So by saying genes and iron consumption aren't related, that iron consumption is the same regardless of genetics, we're taking genetics out of it and making iron a more attractive cause.
And that's why (A) strengthens.
I won't go through the rest of the answers since I imagine the difficulty here is understanding why (A) is right rather than why B-E are wrong. Tricky concept, but one well-worth knowing.
Good luck
The argument here is straightforward enough: from the observation that people with iron-rich diets are much more prone to develop Parkinson's disease than those whose diets contain less iron, the journalist concludes that limiting the consumption of food with a lot of iron (meat, seafood, etc) should reduce the chance of developing Parkinson's.
This is a causal argument--we move from the correlation of iron-rich diets and a high incidence of Parkinson's to the conclusion that iron is a cause of Parkinson's and thus limiting this cause should reduce its effect--and it seems, at least superficially, to make sense. But causal arguments on the LSAT are pretty much always dubious affairs. There's simply a lot that can go wrong when you attempt to tie two events together in an exclusive, active way, as LSAT authors do when endorsing causal relationships. This is why you see causality in so many Strengthen and Weaken questions: its suspect nature makes it ripe for manipulation.
Generally the most effective way to weaken causality (although hardly the only way) is to introduce an alternate cause. Doing so immediately disrupts the presumed relationship and crushes the author's conclusion. With Strengthen questions you very often see the opposite: you can bolster a causal claim by simply removing a potential competing cause. It's not the most powerful support in the world, but it does help: saying that an alternative cause isn't the reason for the observed effect means the author's claimed cause is more likely to be. This is a crucial idea, as it not only happens with some frequency, but it's also at the heart of some of the toughest Strengthen questions: it's just a counterintuitive notion on the surface, that removing/negating something that hasn't been discussed in the stimulus could in fact lend more credibility to the idea in question.
So how does that work here? Well, consider some alternate causes to dietary iron that could lead to a higher incidence of Parkinson's disease, and still fit with the facts as given. What if, for instance, smoking cigarettes is really the reason people get Parkinson's, and nicotine also makes you crave steak/seafood/iron-rich meals? That would clearly weaken this conclusion ("smoking has long been known as both the leading cause of Parkinson's and a trigger for iron consumption" or whatever). So how would you strengthen against that idea? Negate it: "smoking is a well-known Parkinson's contributor and smokers are notorious for diets low in iron." Seems irrelevant at first, sure, but when you think about it you've just removed a competing theory, thereby making the theory on offer more compelling.
That's a demonstration of the principle at work, of course, and not specific to the answers in this question, but hopefully it serves to show the process by which eliminating an alt. cause can, in a rather roundabout way, offer support.
What happens in the correct answer choice in #21 follows the same mechanism. In (A) we're told that people genetically prone to develop Parkinson's don't eat more iron than people without a genetic predisposition. In other words, a genetic predisposition to getting the disease--something that clearly is a cause--isn't related to the high-iron correlation noted in the stimulus, thus making iron, and not genetics, a more likely contributor. We've removed genetics from the equation and, in so doing, made iron's role more prominent. And thus the author's conclusion about iron --> Parkinson's more likely.
To test this, imagine answer choice (A) stated as its opposite: people with a genetic predisposition to Parkinson's consume MUCH more iron than those without those genes. What would that do here? It would destroy the author's view! If a genetic predisposition, something that undeniably makes you more likely to get the disease, also makes you eat more iron (or if the two are for whatever reason associated), then reducing iron is irrelevant--it's your genes, not your diet--and the conclusion can be dismissed. So by saying genes and iron consumption aren't related, that iron consumption is the same regardless of genetics, we're taking genetics out of it and making iron a more attractive cause.
And that's why (A) strengthens.
I won't go through the rest of the answers since I imagine the difficulty here is understanding why (A) is right rather than why B-E are wrong. Tricky concept, but one well-worth knowing.
Good luck
Parkinson's connection, and (D) does absolutely nothing to that relationship)
