You may have heard: moderate drinking helps you live a long time! It’s all over the Internet. It’s a real study, from UC Irvine, so it must be true! Time for me to crack open a breakfast beer.
But wait — are we so sure? When you’re deep into the LSAT, you notice that people in the world are pretty bad at avoiding logical fallacies. In particular, they tend to mix up correlation and causation. That alcohol helps you live longer is a causal claim. Did the research support that claim or merely identify a correlation?
News story after news story failed to clarify. Many articles switched back and forth between correlation and causation as if they were the same thing. Let’s take the LA Times for example. The headline says that moderate alcohol “may help you live into your 90s.” “Help” is causal. But journalists don’t write the headlines. Does the article itself even support that claim?
The article begins, “Those who drink moderate amounts of coffee and alcohol may increase their chances of living into their 90s, according to UC Irvine researchers.” This suggests that the drinking of the coffee or alcohol is the thing that increases the chances of living a long time. Causal claim.
Next up, “The UCI researchers found that consuming roughly two glasses a day of wine or other types of alcohol decreased the chance of an early death by 18% over those who abstained, according to Tribune Media Wire.” That’s causal again. But wait, they’re citing another news outlet. Let’s see what they have to say. I clicked on the link, which in turn cites the Independent.
The Independent, in turn, presents the finding as: “They discovered that those who consumed approximately two glasses of beer or wine a day were 18 per cent less likely to experience a premature death.” That’s just a correlation. People who drank were less likely to die, but there’s no claim that the drinking is to credit. So did these other news outlets just mistake correlation for causation? Maybe those Brits are just better at logic.
Not so fast. The Independent quotes the researcher behind the study, Dr. Claudia Kawas. She said, “I have no explanation for it, but I do firmly believe that modest drinking improves longevity.” So she thinks it’s causal, but doesn’t know why. That’s reassuring.
Almost no newspaper articles I found addressed the question of causation. Were the researchers able to control for confounding variables? I don’t know. This is important because there could be other things that explain why drinkers live longer. Maybe people who are in better health are more likely to drink moderately. Maybe drinking moderately correlates with higher socioeconomic status, which in turn might correlate with a healthier life in other ways. Maybe moderate drinkers eat better. In other words, it’s entirely possible that drinkers might live longer, but that it might have nothing to do with the drinking.
I do have to give credit to livescience.com. They posted an article pointing out that the study had found a correlation but not a causal relationship. Its conclusion is sensible:
Because it’s so hard to tease out cause and effect in studies like these, it’s too soon to say whether moderate drinking is indeed a health benefit, a risk or neither. The bottom line is: If you drink, drink moderately and because you enjoy it — not because you want to live forever.
That seems reasonable enough to me. But livescience.com still doesn’t escape the wrath of the LSAT instructor. The article’s logic is sound, but I’m coming for its headline, “No, Drinking Alcohol Won’t Make You Live Past 90.” The article points out that there might be a causal relationship, but that we just don’t know yet. The headline, on the other hand, claims that there is no causal relationship. That’s an absence of evidence fallacy. Other news outlets may have claimed a causal relationship based on inadequate evidence, but that doesn’t mean that there isn’t a causal relationship. Or, in more general terms, an argument can use crappy logic, but that doesn’t mean its conclusion is false. It’s just not proven true.
In general, flawed logic like this is all around you. As you study for the LSAT, keep an eye out for it. If you’re spotting the flawed logic in everyday life, spotting it on the LSAT will seem like a piece of cake.