PT16.S2.Q21 - several years ago, as a measure

Martin01

Hey, could someone help explain in detail why A is the correct answer choice? I am still lost. Thank you.

Sami

Hi @Martin01

So, lets revisit the conclusion of the stimulus:
The conclusion says:
The decline in the population of gypsy moth is attributable to the poisonous fungus.

Why do the entomologist conclude that:
because they introduced a fungus in the population that was poisonous to caterpillars of the moth and after the introduction of that fungus both the population of caterpillars and adults dropped.

*This is a classic cause and effect argument:
Two things happened together: introduction of fungus and a drop in population (correlation)
From which someone concludes one caused the other: in this case the fungus caused a drop in the population.

So, once we have identified that this is a cause and effect argument, there are a couple of ways we can strengthen a cause and effect argument:

1. To show another example where the cause (fungus) lead to same effect ( a decline in population)
2. To show another example where no cause (no fungus) lead to no effect (no decline in population).
3. Or another alternate cause (maybe a predator or food supply) was not the cause of the effect (the decline in population).
4. Another way you can also strengthen a cause and effect argument is to show that the cause and effect are not reversible. But in this case this wouldn't even work.

Now lets take a look at answer choices.

A) A strain of gypsy moth unaffected by the fungus has increased in its share of population. This is very similar to our prediction above in #2. Where no cause, as that particular strain of gypsy moth is unaffected by the fungus, did not lead to a decline in that gypsy moth's population. (no cause no effect) (so this is correct)

* Another example: lets say we give someone an antibiotic, and their bacterial infection goes down. Sure it could be antibiotic that caused the decline in infection, but it could also be a healthy diet or the the body's own immune system that was responsible for the decline in infection. But if I tell you, that all the bacteria resistant to that antibiotic have survived, then we can say (maybe not with 100% certainty) but at least with a bit more certainty) that the decrease in bacterial infection might have been due to the antibiotic. This is strengthening the argument by a bit.

* what makes strengthening questions difficult is that the answer choice will not 100% strengthen the conclusion, sometimes its as weak as 1%. Our job is to find one that will strengthen the relationship between the premise and the conclusion, in this case the fungus causing a decline in the moths population.

The fungus is also poisonous to other species. Well the question that I am left with after reading this is, did it kill other species as well? we just don't know. So just because something is poisonous does not mean that it is automatically the cause of death for other species, if we don't even know if other speciies were affected by it.

C) Here we are talking about an increase in the numbers of gypsy moths (already the argument is giving us information that conflicts with our premises in stimulus) , then the answer choice says that this was followed by a drop in the number of their predators. Although, this is an interesting phenomena, 1. it gives us contradictory information than our premises in stimulus so it definitely does not strengthen the argument 2. Its kind of irrelevant if their predators died. Also, I think this is expected that if a food source dwindles the species who prey on it will also have a decrease in its population. So this answer choice just has a whole lot of problems, lets eliminate it.

D) This answer choice says, acid rain has caused a decline in the Oak tree populations. This would be a great correct choice if we wanted to weaken the stimulus above. Because this give us an alternate cause of why there was a decline in the population of moths; it was not the fungus but a decrease in the food supply of the moths, in this case the oak trees which they depend upon.

E) The current decline in the population of the moths is not greater than the decline that has occurred in other forests. This is another great answer choice if we wanted to weaken our stimulus above instead of strengthening it. This is because the other forests where there was the same amount of population decline as in our stimulus above actually means that they also had the same effect (decline in our moth population) but without the cause (fungus). So this does not strengthen our relationship between fungus causing the decline in our population of moths, if other forests are having the same decline in moth population without the fungus, it maybe says the population decline is probably due to something other than fungus.

For example: There is an lsat stimulus which says that a hunting ban in a particular town caused the deer population to grow. This is another cause and effect argument, and it helps to start seeing patterns. But lets say an answer choice says, that other towns in which there was no hunting ban also had a rise in deer population. This would weaken the link between the hunting ban on deers being the cause of the rise in deer population as other towns did not have the same cause (the ban on hunting deer) but had the same effect (rise in deer population).

* overall, this type of stimulus (a cause and effect argument) is very prevalent in LSAT and you are sure to see it again and again. I hope this helped break down the argument. Let me know if you have any questions.

Also, here is a list of videos that will help you understand cause and effect types of arguments:
https://7sage.com/lesson/causation/
https://7sage.com/lesson/causation-theory/?ss_completed_lesson=1207
https://7sage.com/lesson/correlation/?ss_completed_lesson=1206
https://7sage.com/lesson/correlation-ideas/?ss_completed_lesson=1205
https://7sage.com/lesson/4-possible-explanations/?ss_completed_lesson=1204
https://7sage.com/lesson/chronology/?ss_completed_lesson=1203
https://7sage.com/lesson/causation-strategy/?ss_completed_lesson=1202

Also, if you click next, the core curriculum will give you more examples LSAT questions that are based on cause and effect argument type.

I hope this helped. Let me know if something was not clear or I did not explain well : )


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Martin01

Thank you so much!

Sami

My pleasure : )