Ulterior Motives

How goals, both seen and unseen, drive behavior

Is That Extra Hour of Study Time Worth It?

When students lose sleep, their performance suffers.

It is no surprise that teens and young adults are a pretty sleep-deprived group.  Yesterday morning at 9am, for example, I taught a small class here at the University of Texas.  The students staggered into class looking like they could use a nap.  I also have three teenagers.  They generally stay up late and get up early during the week, hoping to catch up on weekends by sleeping all morning.

There are lots of distractions in the modern world that lead people to stay up late in the night.  For students, though, there is also homework.  On the night before a big exam or a major paper, many students put in a lot of extra study time in order to prepare. 

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Does that extra study time help performance in school?

This question was explored in a studying the January, 2013 issue of Child Development by Cari Gillen-O’Neel, Virginia Huynh, and Andrew Fuligni.  They tracked a group of high school students in 9th, 10th, and 12th grade.  At each grade level, students filled out a daily diary for 2 weeks. 

Every evening during the study, the students rated the amount of sleep they got the day before, the amount of time they spent on homework, and they answered questions about any academic problems they had the previous day (like doing poorly on a test and having difficulty understanding new material).

Overall, there was a tendency for high school students to sleep less as they advanced in school.  So, the 9th-grade-students slept an average of 7.6 hours a night, while the 12th-graders slept only 6.9 hours per night.  Students experienced fewer academic problems as they advanced in school.  That means that students are actually learning better school skills over the years. 

The most important result, though, was that when students lost sleep because they spent extra time doing schoolwork, they had significantly more problems the next day than when they got their typical amount of sleep.  This negative effect of extra study time was strongest for 12th-grade-students and weaker for the 9th- and 10th-grade students.

What is going on here?

Sleep is important for many reasons.  It helps memory.  You consolidate memories during sleep.  Sleep also helps you focus and sustain attention.  Sleep also gives you energy to be active.  You are much more likely to be a passive learner when you are tired.  And you learn less when you are passive then when you actively engage with new material.

So, why are high-school Seniors hardest hit? 

The 12th-graders are sleeping least to begin with.  They are just at the edge of their ability to function properly.  When they disrupt their sleep schedule further with extra study, it has strong repercussions for the next school day.  The 9th- and 10th-grade students are a bit more resilient, because they are not as strongly sleep-deprived.

What does this mean?

First off, this study reinforces the general observation that teens and young adults are not sleeping enough.  Getting even an extra 30 minutes of sleep a night would be a huge benefit for this group.

Second, it means that students need to try to spread their work out over longer periods of time.  It is an age-old tradition to cram for exams and to finish papers at the last minute.  There are lots of good reasons to want to avoid cramming.  For example, cramming for an exam may help a student pass that particular exam, but information learned the night before the test is not remembered in the long-term as well as information that is studied over several nights.  If cramming for a test also reduces the amount of sleep a student is getting, then that just adds to the problem. 

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Art Markman, Ph.D., is a cognitive scientist at the University of Texas whose research spans a range of topics in the way people think.

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