Causality on the GRE
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You may have heard the maxim “correlation does not imply causation” before. It’s a common expression, but what does it mean for your GRE score? Lots.
Suppose you develop a bad stomachache. Where does your brain go? Most of us start to analyze the past few hours or days to seek a reason, an explanation, or—in GRE terms—a cause for that stomachache. What did I eat? Am I stressed out? What did I drink? Is it something worse? Appendicitis?
If you’re superstitious, you may start attributing odd and unrelated causes to your ache. Was it that black cat that crossed my path? Did I forget to knock on the door three times? Are my mortal enemies in the underworld stabbing a voodoo doll?
A huge part of our intelligence as a species is linked to our ability to figure out WHY events occur. If your caveman pal Ogg suddenly turns purple and dies, you have a vested interest in knowing the cause of his death, so you don’t eat the same berries. Those who attributed causation properly survived.
Causality lies at the heart of science (Why is the universe here? Why did we evolve thumbs?), criminal justice (Who shot J.R.?), and politics (Why did the economy decline? Who or what is responsible for the change in crime statistics?).
You’ll see causality on the GRE all over the Verbal section in many Reading Comprehension passages, especially the logic-based RC questions, not to mention the Analysis of an Argument writing sample.
What You’ll See
An event occurs that begs an explanation (The dinosaurs go extinct. The earth develops a moon. A company’s profits increased.). The passage may also list another event that occurred at the same time or right before it (correlation). The author eventually concludes that one event (A big volcano. A giant meteor. An increase in sales.) best explains why that event occurred (causation).
The GRE will then ask one of several questions related to that conclusion:
-What assumption is the author making?
-What would best strengthen that conclusion?
-What would weaken that conclusion?
Take two events: Event A and Event B might have happened close in time, or one right before the other. This is called “correlation.” If the author of the argument makes the conclusion that A was the cause of B, this is called “causation.”
Anyone who leaps to this conclusion is making a pretty big series of assumptions:
– A was the ONLY cause of B.
– There was NO OTHER cause of B.
– B didn’t cause A.
– It’s not a coincidence.
Back to my stomachache: At a street festival, I ate some undercooked chicken skewers (Event A). Later, I got sick (Event B). Therefore, I must have gotten sick because of the chicken (A caused B).
This is a classic causal argument, and my conclusion may or may not be correct. (Keep an eye out for keywords: due to, result of, cause, because, reason why, etc. to help spot these.)
Once you spot a causal argument on the GRE, ask a few questions.
Could there be other causes?
Perhaps multiple causes? If a friend of yours, George, lost a lot of weight recently, he might claim it was due to his diet alone. Sure, it might be due to diet. It might also be due to exercise. It might also be due to illness, surgery, or a myriad of other causes.
The most common assumption is “No other causes.”
“George made no other changes to his lifestyle other than diet.”
On the GRE, to strengthen an argument like this, look for an answer that removes other causes.
“George did not increase his level of activity.”
“George did not recently undergo drastic surgery.”
To weaken, suggest another cause.
“George adopted a vigorous exercise regimen.”
Could cause and effect be reversed?
Suppose an argument finds a correlation between heavy drinking and depression. “People who drink more than 5 drinks a day are, on average, more likely to suffer from depression than those who do not. Therefore, drinking is a cause of depression.”
That might be the case. However, it’s also likely that people who are depressed are more likely to drink heavily, and therefore the depression caused the drinking.
The assumption is that the cause was before the effect.
To strengthen this, prove the cause came first.
To weaken it, prove the cause came second.
Could it be a coincidence? Would it have happened anyway?
Coincidences may be the source of all superstition. Somebody broke a mirror and later had some bad luck, a correlation becomes a causation in someone’s mind, and a superstition is born.
You’ve often heard the argument that marijuana is a “gateway drug.” It’s easy to reach this conclusion: if you ask all the heroin addicts in the world whether or not they smoked pot, perhaps 99% will say yes. Sounds like a compelling link, eh?
However, you have to ask yourself the opposite question. How many pot smokers go on to use heroin? That percentage is MUCH smaller.
By the same logic, by the way, you can prove that milk is a “gateway drug” to serial killing. Every serial killer drank milk, right?
What happens if you remove the purported cause?
Does the effect go away or does it remain? In medical studies, this is called a “control” group.
If you believe you have a gluten allergy, the best way to test it is to cut gluten out of your diet and make NO OTHER CHANGES to your diet or lifestyle whatsoever. If your symptoms disappear, you may be allergic to gluten. However, there are always other causes to consider: placebo effect, a lack of excess calories, etc.
To sum it up:
- Keywords: due to, result of, cause, because, reason why, etc.
- Conclusion: Event A caused Event B (causation).
- Premises: Event A occurred. Event B also occurred (correlation).
- Assumptions: Event A is the only cause. There are no other causes. Event B did not cause Event A (not reversed). It’s not a coincidence.
- To strengthen: Provide evidence for a causal link. Eliminate potential other causes. Show that the purported cause happened first (and very close in time). With a control group, show what happens when you remove the proposed cause (no cause = the effect should go away).
- To weaken: Show evidence of another cause. Prove it was a coincidence. Show the cause without the effect. Show the effect without the cause. Show that B was actually the cause of A.
Keep an eye out for causality on the GRE and it may cause you to get a higher score!
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When not onstage telling jokes, Neil Thornton loves teaching you to beat the GRE and GMAT. Since 1991, he’s coached thousands of students through the GRE, GMAT, LSAT, MCAT, and SAT and trained instructors all over the United States. He scored 780 on the GMAT, a perfect 170Q/170V on the GRE, and a 99th-percentile score on the LSAT. Check out Neil’s upcoming GRE course offerings here or join him for a free online study session twice monthly in Mondays with Neil.