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Unambiguously Good News about Teens and Sleep
Andrew Watson
Andrew Watson

You read that right. I mean: it’s really good news about teens and sleep.

We all want adolescents to sleep more. Better said, we know that they need to sleep more.

teens and sleep

More sleep should benefit, say, their mental health, their physical health, and their academic performance.

Heck, they should just feel better.

One Obvious Solution

If teens’ biology prompts them to stay awake later and wake up later (it does), then we could help adolescents sleep more by starting high school later.

Although obvious, that solution has two important flaws:

First: we haven’t tested its efficacy.

Second: teens might just stay up later, and thereby rob themselves of the extra sleep we’re trying to provide. We just don’t know. (See previous paragraph.)

Here’s the first part of unambiguously good news: researchers have now tested the solution.

The city of Seattle, Washington delayed high school start times from 7:50 am to 8:45 am. Researchers measured lots of student behaviors both before and after that change. What did they find?

Teens and Sleep: Obvious Solutions Work!

First: students slept more. They got, on average, 34 minutes of extra sleep: from 6 hours 50 minutes to 7 hours and 24 minutes.

Second: they got higher grades. The average among measured students rose from 77.5% to 82%.

(The researchers hesitate to make strong causal claims; something else might account for the better grades. But, it’s a highly plausible hypothesis that extra sleep helped them learn more.)

Third: at one of the two high schools, first-period absences fell. (At the second, the absence rate remained constant.)

The researchers don’t make a strong argument about the reason for this difference. They do note, however, that the improving school has a higher percentage of economically disadvantaged students. Perhaps the combination of early start times and low SES made on-time arrival especially challenging.

Methodology

Part of the unambiguously good news: this study boasts particularly strong methodology.

In particular, it doesn’t rely on student self-reports — as so many sleep studies do. Instead, it asked students to wear a wrist monitor that tracked their activity levels.

Also, it took both pre- and post-change measurements. That is: they didn’t wait until after the change and then start measuring. Instead, they got a solid baseline, and then compared the after-effects to that baseline.

A final note: this article says that other school districts — and even states — are contemplating similar changes. Here’s hoping they follow through. And, here’s hoping that parents support these changes.

10,000 People Talk About Sleep and Cognition
Andrew Watson
Andrew Watson

Most of the research studies I read include a few tens of people. Sixty or eighty is good; more than 100 is rare. I’ve seen published studies with an even dozen.

sleep and cognition

So when I hear about a study with over 10,000 participants, I sit up and take notice.

In this case, researchers in Canada asked people to fill out online surveys about sleep, and to take cognitive tests. Given their astonishing data pool, they can reach firm conclusions about the questions they’ve asked.

Sleep and Cognition: Firm Conclusions

Some of these conclusions will sound quite predictable. Others will surprise you. They certainly surprised me.

First, if you want optimal cognitive function, roughly 7-8 hours of sleep gives you the best results. (Assuming that “you” are an average person. Of course, not everyone is average.)

Second, that number doesn’t change with age. (See below for an important caveat.) That is: 30-year-olds and 80-year-olds think best with the same amount of sleep.

Third, too much sleep muddles cognition as much as too little sleep. As someone who likes sleeping, I’m sorry to say this but: the graphs don’t lie.

Fourth, non-optimal sleep doesn’t harm short-term memory. Researchers tested short-term memory with the “spatial span task.” Participants had to remember which boxes flashed green, and press them in the same order. Here’s an example:

https://www.youtube.com/watch?v=zWO_w3m4NQs

Instead, non-optimal sleep fuddles reasoning skills (like executive function and deductive reasoning) and verbal skills (like verbal working memory).

Of course, school requires A LOT of reasoning and verbal skill. No wonder sleep-deprived (or sleep-surfeited) students struggle.

(By the way, fifth, 48.9% of the participants didn’t get enough sleep.)

And, sixtha good night of sleep really does help. That is: people who got even one good night’s sleep before the test saw a measurable uptick in their cognitive performance.

Caveats

From a researcher’s standpoint, it’s important to note that this team didn’t draw on a random sample. These participants volunteered by coming to a particular website.

And, all of the data here come from self-report. People could be deceiving the researchers. They could also be deceiving themselves.

From a teacher’s standpoint, we should note the age cut-off for this study: 18 years. K-12 students might see similar patterns. That is: their short-term memory might be fine after low-sleep nights, while their reasoning and verbal skills suffer.

Or, entirely plausibly, younger people might see different effects. We just don’t know.

A Final Note

In my experience as a high-school teacher, my colleagues (and I) experienced sleep deprivation as much as our students did.

We should, of course, encourage our students to get enough sleep. (We should also schedule the class day to fit our students’ sleep cycles.)

Now that we’ve seen this research into the connection between sleep and cognition, we should also take better care of ourselves.

Solving the Nap Research Problem (BTW: Naps Help!)
Andrew Watson
Andrew Watson

Do naps improve learning?nap research

If you teach teenagers, you almost certainly want to know the answer to that question. Whenever I talk with adolescents about brains, it’s one of the first questions I get.

Alas: an important muddle makes that question noticeably hard to answer.

The Nap Research Problem Explained

On the one hand, we’ve got plenty of research showing that naps boost learning.

If I give you a list of words to study, you’ll remember more of them after a nap than you would if you hadn’t taken that nap.

In one study, for example, Olaf Lahl found that

“An ultra short period of only 6 min of napping is already sufficient to significantly boost declarative memory performance beyond waking control levels.”

You read that right. Even a SIX MINUTE nap helped participants recall more words.

But wait: there’s a problem.

We know that good night-time sleep is essential for consolidation of long-term memories. (Here’s a great article on the subject.)

It seems plausible to me that an afternoon nap might feel good at the time, but might make it harder to sleep at night.

If that’s true, then the short-term benefit of the nap will be more than offset by the long-term detriment of a bad night’s sleep.

In other words: I might remember that list of words better after the nap, but I might be likelier to forget everything else.

This uncertainty has always held me back from recommending naps.

The Nap Research Problem, Solved

Researches in Jintan, China looked at the cognitive results of napping — and their method fixes this research problem.

They gathered nap and night-time sleep data from 363 6th graders. And, they tested them on a variety of cognitive functions: executive control, spatial memory, and complex cognition among them.

What did they find?

First: frequent nappers get better nighttime sleep than infrequent nappers.

Yup: naps didn’t make it harder for these 6th graders to sleep. In fact, they slept better.

Second: frequent nappers did better on a variety of the cognitive tests. For instance, they did better on tests of sustained attention. (In schools, we require A LOT of sustained attention).

They also did better on tests of non-verbal reasoning.

In brief: frequent naps don’t make it harder to sleep at night, and they do improve some cognitive functions. Win win!

Nap Research in Context

This study’s authors wisely note two key limitations.

First, the data on sleep come from self-reports. This method, alas, allows for participants’ faulty memory to skew the results.

Second, the study took place within a particular cultural context. Naps are a cultural norm in China. That norm just might have an influence on the relationship between napping and cognition.

We just don’t know.

(To think more about the important of context, consider the perils of WEIRD neuroscience.)

For me, this study’s specific findings about cognitive capabilities are interesting. However, its general finding that naps don’t interfere with nighttime sleep means that the other studies about naps’ benefits can be taken at face value.

So: you’d like to take a 6 minute nap? GO FOR IT!

Chronotype Influences Grades. Owls Are Sad…
Andrew Watson
Andrew Watson

You’re up before the sun rises, eager for the day’s adventures? Sleep researchers call you a “lark.”

Chronotype Influences GradesYou’re perkiest after midnight, happily contemplating the world while your friends sleep? They call you an “owl.”

If you’re comfortably in the middle, think of yourself as a “finch.”

Sleep researchers know a lot about these three sleep species.

And their insights help teachers and administrators think more carefully about helping our students learn.

Point #1: Where do chronotypes come from?

Simply put: genes.

Or, to quote a recent article:

Chronotype appears to be largely determined by the genetic composition of an individual’s circadian clock. An individual may be able to choose to change their sleep/meal/activity time due to day-to-day schedule impositions, but they may not be able to shift their internal clocks in the same way, due to its genetic basis.

I want to emphasize the rarity of this explanation. In the worlds of psychology and neuroscience, almost everything results from a combination of nature and nurture.

IQ? Nature and nurture.

Grit? Nature and nurture.

Processing speed? Nature and nurture.

So: don’t let this one instance fool you into thinking that genes routinely determine our fates.

Of course, age has an influence on chronotype as well. Puberty magically transforms more of us into owls. As we age, we might well revert to our initial larkiness — or at least to finchitude.

Note well: students have no control whatsoever over either of these influences. They can’t control their genes, and they can’t control their developmental stage.

In other words: adolescent owls aren’t simply being stubborn when they go to bed late. They’re often simply not tired enough to sleep.

Point #2: Chronotype Influences Grades

Researchers Smarr and Schirmer looked at the relationship between chronotype and grades in college.

Their finding? In brief: we do best when class time matches our chronotype.

Larks do best in morning classes. Owls catch up in evening classes.

However … and this is a BIG however … owls consistently have lower GPAs than larks and finches.

Even in evening classes, larks and finches have higher GPAs than do owls — although the difference is smaller than in morning classes.

One explanation  — favored by morning people everywhere — is that larks are simply smarter than owls.

A better explanation: school schedules benefits larks and make life difficult for owls. After all: when classes begin early in the morning, owls just don’t get enough sleep before class.

And — as you remember — these sleep-deprived owls aren’t being stubborn. They’re just not tired enough to fall asleep in time to get the 8 or 9 hours they need.

In other words: we teach owls, larks, and finches. Our school schedules should work well for all of them. When we favor one sleep species over another, we needlessly disadvantage real students who want to learn.

“Not Just a Decadent Luxury”: The Power of Naps
Andrew Watson
Andrew Watson

We know that sleep is good for learning. But what about NAPS?

Over at BrainBlogger, Viatcheslav Wlassoff summarizes research suggesting that naps yield clear benefits for cognition, attention, and emotion.

power of naps

Although I find research into the power of naps generally persuasive, I do worry about an important gap. Do naps interfere with sound night-time sleep?

That is: Wlassoff summarizes research showing than naps help sleep-deprived people. Do they help non-sleep-deprived people? And, do they make it harder to get a full night’s sleep?

If yes, then the short-term power of naps might create longer-term problems.

If you know of research that answers this question, I hope you’ll let me know.

Sleeplessness Harms Women’s Thinking More Than Men’s?
Andrew Watson
Andrew Watson

You can understand why this study lit up my twitter feed recently. It makes a remarkable claim: women — but not men — experience working memory declines after a sleepless night.

Why We Care

We have at least two powerful reasons to care about this study.

First, it makes strong claims about gender differences. According to lead author Rangtell (and 8 colleagues), women’s performance on a working memory task gets worse after a sleepless night.

On the other hand, men’s working memory performance remains just as good as when they had a cozy 8-hour sleep.

(I’ve written about gender differences before. You may recall that I’m often skeptical of specific claims, but do think that there are some important differences at the population level.)

So, this study plays an important role in the ongoing debate.

Second, Rangtell’s study focuses on working memory. And, working memory is really important in school.

What is working memory?

When a student works on a word problem in math, she first has to select the key information from the sentences. Then she holds that information in mind. Third, she reorganizes all that information into the correct formula. And finally she combines pieces of that formula appropriately: for example, she combines “7x+8x” into “15x.”

Whenever students select, hold, reorganize, and combine information, they’re using working memory.

And, our students do that all the time. They use working memory to conjugate a new Spanish verb. And, when they apply new terminology (“protagonist”) to a specific book (“Sethe is the protagonist of Beloved.”) And, when they balance chemical equations.

Basically, schools are shrines we build to honor successful working memory functioning.

If there truly is a gender difference in working memory function, that’s a really big deal.

Sleeplessness Harms Women More Than Men?

This study is, conceptually, very straigtforward.

Ask some people to do a working memory task after a full night’s sleep. Then, ask them to do the same task after they’ve been up all night. Is there a difference in their working memory performance?

sleeplessness harms women

Rangtell and her colleagues say: for men, “no”; for women, “yes.”

However, this study includes a very serious problem. The task that they use to measure working memory DOESN’T MEASURE WORKING MEMORY.

(You read that right.)

The researchers asked these people to listen to a list of numbers, and then type those numbers into the computer in the same order.

That’s simply not a test of working memory. After all, the participants didn’t have to reorganize or combine anything.

Instead, that’s a test of short-term memory.

Now, short-term memory is related to working memory. But, “related to” isn’t good enough.

Imagine, for instance, I claimed that sleeplessness makes people shorter. The way I determine your height is by measuring the length of your arm.

Of course: arm length and height are related. But, they’re not the same thing. Tall people can have short-ish arms. I can’t measure one thing and then make a claim about a related but different thing.

So too, Rangtell can’t measure short-term memory and then make claims about working memory. She didn’t measure working memory.

Does sleeplessness harm women’s working memory more than men’s? We just don’t know.

(By the way: I’ve reached out to the lead researcher to inquire about the working memory/short-term memory discrepancy. I’ll update this post if I hear back.)

An Extra Half-Hour of Sleep? An Extra Hour?
Andrew Watson
Andrew Watson

AdobeStock_80298747_Credit

If you’ve ever met a teenager, you might be skeptical about the idea of starting high-school classes later. After all, you might worry that they’ll just stay up later. They are, after all, teenagers…

What does research on high school start time say?

According to a recent study done by Penn State researchers, you needn’t worry. Later high-school start times do in fact translate into more sleep.

Specifically: students whose first class started later than 8:30 got between 27 and 57 (!) more minutes of sleep. Imagine just how much more learning might happen if a teen regularly got an extra hour of sleep.

The researchers based these conclusions on sleep diaries that lasted only a week; I’d be more persuaded if they had data from a longer period of time.

However, this finding does echo a conclusion that I reported on back in April. Given these converging data–and, frankly, common sense–I’m inclined to believe that later start times really do help students get more sleep.

Bright Screens and Sleep
Andrew Watson
Andrew Watson

AdobeStock_36204426_Credit

Here’s a handy review of the effects that bright computer and tablet screens have on sleep. (Hint: they’re not helping.)

Author Viatcheslav Wlassoff concludes with a few simple hints on how to reduce the detrimental effects of screens on melatonin.

Parents, High School Start Times, and Sleepy Teens
Andrew Watson
Andrew Watson

AdobeStock_39639084_Credit

Research findings that support later high-school start times have been more and more common in recent years. (See also here.) And teachers I know are increasingly vocal about letting teens sleep later.

And yet, when I talk with high school leaders, they ruefully cite sports schedules to explain the impossibility of making serious changes.

(I’ve also read that bus schedules get in the way.)

Here’s another–quite surprising–reason that this change might be hard to accomplish: parental uncertainty. According to this recent study, published in the Journal of Clinical Sleep Medicine, half of parents whose teens start school before 8:30 don’t support a later start time.

The study concludes that we need to do a better job educating parents about the biological changes in adolescent sleep patterns.

The more that parents understand how melatonin onset–and, hence, sleepiness–changes with adolescence, the more they might understand that their awake-at-midnight teens aren’t simply being willful. They are instead responding to powerful chemical signals.

Given all we know about adolescent sleep, and the effect of sleep on learning, teachers and parents should be champions of reasonable high school start times.