Stay Up Late, Made Bad Grades?

Some recent research by psychologists at Hendrix College shows a negative correlation between how late college students stay up at night and their GPA.

Refresher on Correlational Research:
1. Correlation - two or more things are co-related. They move in relation to each other.
2. Negative Correlation - when one goes up, the other goes down (or vice versa).
3. Positive Correlation - when one goes up, the other also goes up (or they both go down).
4. No Correlation - one's movement has no relationship to the other's.
5. Correlation does not imply causation - simply because there is a correlation between two things, it does not mean that one causes the other to move.

Now, about the college students' sleep patterns and grades.

Freshmen who described themselves as "late to bed" had a lower grade average at the end of the school year than either those who described themselves as "early to bed, early to rise" or "somewhere in the middle."

Did the staying up late cause the lower grades? Did the lower grades cause the students to stay up later? Or, was there a third factor that caused both of them?

Mothers might be tempted to say that the staying up late caused the lower grades. College professors might be tempted to say that there was a third thing causing both. Remember, these are college Freshmen, away from home for the first time. No momma to get them up in the morning, remind them to do their homework, or get plenty of sleep.

Either way, this research doesn't tell us, because it is correlational research. To determine cause, we need a controlled environment in which we can manipulate one variable at a time, to see if changing that one thing makes a difference. That describes experimental research.

However, I am willing to go out on a limb and say that staying up late is what causes students in my early morning classes to sleep during my lectures. Of course, someone else might suggest that the reason they sleep is because my lectures put them to sleep.