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I came across an article a couple weeks ago citing data that purportedly shows the GMAT scores of MBA students to be “much higher in both men and women that went to bed later and arose later.”

The author suggests the findings are in line with a long-established link between bedtime and intelligence. Specifically, Study Magazine explored the correlation with a detailed analysis of sleep and wake up times according to IQ. The findings revealed that people with IQ’s less than 75 went to bed by 11:30 pm or earlier while those with IQ’s of 125 and above went to bed after 12:30 a.m.

So what do you think? Are you buying it?

Correlation vs. Causation

One of the foundational “Logic 101” concepts we teach in our GMAT Critical Reasoning lessons is that there’s a difference between correlation and causation. Just because two things are correlated doesn’t mean that one causes the other.

Take, for example, the following spurious correlation:

spurious correlation between per capita cheese consumption and the number of people who died by becoming tangled in their bedsheets
Beware spurious correlations on the GMAT that claim a cause-and-effect relationship.

Looking at the data points, cheese consumption and death by bedsheets move in lock-step with each other!

But while it’s sort of funny to think about (in a morbid sort of way), do we really thinking that eating cheese causes you to become tangled up in your bedsheets and die? No, that seems pretty unlikely.

Likewise with this study showing a connection between GMAT scores and sleep/wake times. While it doesn’t do us any good to dispute the correlation between the two (the findings are what they are), what we can do is question the cause-and-effect relationship.

And bringing this back to the GMAT, that’s exactly what you want to do on Critical Reasoning questions involving cause-effect arguments. If a CR question asks you to “weaken the argument,” for example, the best way of doing that is to show how something else might in fact be causing the outcome we see (we call that a confounding factor in statistics).

Here, if going to sleep late isn’t actually the cause of higher GMAT scores, what might be? Well, there are any number of possible explanations. Perhaps people who go to sleep late do so because they have over-active minds, and those over-active minds indicate higher brain function. Perhaps people who go to sleep late also wake up later and actually get more sleep than the average person, and that extra sleep helps the brain to recharge and clarity of thought to increase. Or perhaps night owls are disproportionately right-brain people who also happen to be more quant-dominant, a valuable trait when it comes to doing well on the GMAT.

The point is, there are a lot of possible explanations for why people who stay up late tend to do better on the GMAT — but it’s not the staying up itself that’s the cause.

Or who knows, maybe it really is! Just as we can weaken arguments by showing possible confounding factors at play, we can also strengthen arguments by showing how the proposed causal agent is in fact the most likely explanation.

One observer of the sleep-IQ link, Lauren Martin of Elite Daily, suggests that there is an actual causal relationship there, and it all has to do with reflection:

“Only after dark can we learn, absorb and study the effects of the day. It’s a necessary self-reflection that few humans take the time to make. There’s something to be said about those who fight the urge to sleep and explore that block of uncharted time that so many who always have their eyes closed will never see.”

So will that extra reflection time help you get a few extra points on the GMAT? I’ll leave that to you to decide.

As for me, I like my 7-8 hours of sleep to start around 11:00pm. But then again, I’ve already dominated the GMAT ?.

Now it’s your turn! Let us help. Check out our comprehensive GMAT prep courses and choose the one that’s right for you. We’re looking forward to working with you!