Psychology is in Sara Mednick's blood. The daughter of psychologist Sarnoff Mednick, who studied schizophrenia as well as the genetic roots of criminal behavior, she was steeped in scientific questions from a young age.

She went to Harvard for graduate school, but "burned through several thesis topics" before coming to the lab of Robert Stickgold, who studied sleep and memory. Digging through the research literature, she found that while nighttime sleep was well studied, naps were uncharted territory.

Now an assistant professor at the University of California, San Diego, Mednick has done several studies showing naps can sharpen memory, improve learning, and quicken fine-motor skills. People who take a nap do better than non-nappers at remembering word lists, picking out the oddball shape in a field of uniform ones, or even linking seemingly unrelated concepts using a word association test.

Not content to keep her research in the ivory tower, she has taken it on the road, preaching the gospel of napping to the common man, corporations, and even Good Morning America. She published a book called Take a Nap! Change Your Life, which prescribes naps at certain times of the day to enhance creativity, motor skills, or alertness. She even organized a "Nap In" at UCSD last spring, where students were handed sleep masks and a map to the best snooze spots on campus. "I think we need to have a little more of a take-back-the-nap attitude!" she told the audience.

At the February 2010 American Association for the Advancement of Science meeting in San Diego, Mednick met with SciCom's Tia Ghose to discuss her latest findings on naps and memory. She chatted about why we sleep, why some naps are better than others, and which country has the best attitude toward the afternoon siesta. (Hint: It's not the U.S.)

Your father is also a psychologist. How did he influence you?

I grew up going to his lab. Even when I was a really little girl, he would tell me about research and scientific questions. The most fun scientific conversations I've had were with him.

But he's also a big napper?

My dad swore by napping. He's got a way with the world, so I wondered: Why is he enjoying it so much? What's he getting out of it?

That's why you decided to study napping?

Well, originally I was studying nocturnal sleep. Nobody had ever really studied napping, and it was easier to do napping than to do nocturnal sleep research. So I set up a little nap room in the psychology department, learned how to do PSG, and just started.

What's PSG?

Polysomnography. The EEG you have on during sleep to test if you're awake, asleep, and what brain stage of sleep you are in.

Speaking of stages of sleep, what actually goes on in our brains while we're sleeping?

That depends on what brain state you're talking about. So at first your brain goes from a very active waking state to a dampened sleep state.

There's a switch between waking, to stage two, to slow-wave sleep. Blood flow starts to slow down, temperature starts to decrease, and neurons start to interact on these very slow, high-amplitude, low-frequency waves. That's all the way through non-REM sleep.

Then, during REM [rapid eye movement] sleep, your brain goes from being very, very low activity—dampened brain activity—to very, very high activity. Your brain areas start to really talk to each other a lot more. You have these rapid eye movements, but your body is atonic [has no muscle tone], and you have very fanciful dreams.

What's the purpose of these different stages?

Different sleep stages tend to enhance different types of memory. Stage two seems to enhance anything with coordinated muscle movements, like playing piano or typing. Slow-wave sleep seems to enhance memories that you consciously try to remember, such as remembering a list of words or a spatial map. REM sleep seems to enhance memories that you do not consciously try to manipulate, such as your visual memories and your creativity.

In your book, you have certain formulas: Naps earlier in the day maximize creativity, while mid-afternoon siestas boost alertness. What's the logic behind that?

The idea behind the nap wheel, which is on the cover of the book, is to show you that if you want to maximize one kind of memory over another, you might want to take a nap that either has more REM sleep or more slow-wave sleep. And then the nap wheel shows you what time of day those naps should be occurring. Any time within six hours after you wake up is going to be a high REM time. Any time after that is going to be high in slow-wave sleep.

But this nap formula is based on studies in controlled environments. The tasks you have people do don't look much like composing an opera or solving the structure of DNA. Can we really make the leap from a word association test to creativity?

Well, these studies usually come out of inspiration from the real world. It's not a secret that dreamtime has had a lot of influence on people throughout history who needed creative insights. August Kekulé, who discovered the benzene ring, had a dream where he woke up and he imagined these snakes with their tails being eaten by each other.

"Japan is very, very good with napping. They honor people who take naps. America is probably the worst culture in regard to sleep."

We are distilling these cognitive processes so dramatically into little tasks, so I could see why you're saying: How is that relevant to the real world? At the same time, all of these tasks are building blocks for much more complex cognitive processes. If you have evidence that the building blocks are affected, it's quite likely that what's going on downstream is affected.

Have you tried it yourself?

I actually once wrote a song that way. I knew what I wanted to be in the song lyrics, so I took a nap where I knew I'd have a lot of REM sleep. And I woke up and there was this whole song in my head.

You do a lot of public speaking. Is it hard to navigate between the incremental findings of your research and broader claims you have to make for the general public?

I stay within the boundaries of what I feel comfortable. I don't ever say anything that I can't back up with a lot of data. A lot of the talks I give to the general public are just all data. So I don't find it to be a problem.

Is it hard to find students to participate in your studies?

Never. Pay them to nap [laughs], and it's pretty much a sure thing.

A lot of people say they hate to nap. Is it possible naps just aren't good for some people?

My guess is that a lot of the reasons why people don't nap are self imposed. Probably, if people wanted to, they could nap. But that is just my hypothesis; I haven't really tested that out.

But some people wake up feeling groggy.

One reason we talk about is sleep inertia. Some people just don't feel good. I believe you can train yourself not to go into slow wave sleep [which causes the groggy feeling].

But is there any way you can know, before you wake up, that you're in a certain stage of sleep, say REM?

You can wake up and just feel like you were dreaming and you would know. But other than that, so far no. . . . There are probably a lot of people with gadgets out there [laughs], or products on SkyMall that say they could, but so far, no.

What about people who say naps prevent them from sleeping at night?

Usually those are only people with insomnia. Those people really do need to listen to their sleep doctor if they're on a sleep-restricted schedule. But for other people, we've shown there isn't really that much effect on their nocturnal sleep. You just don't want to be taking a nap within three hours of your bedtime.

What do other animals do for sleep?

Most animals are multiphasic, so they sleep more in naps.

Is there any way to just completely forgo sleep at night in exchange for round-the-clock naps?

There are people who do that: über-men nappers who just nap, or they do something called an everyman nap, four hours of core sleep and then nap for the rest of the day. Sometimes you hear really positive stories, and sometimes you hear about deteriorating health and lack of social life because they need to sleep and everyone else is awake and vice versa.

Those people have not really been studied much. That's the question for us as scientists. People are doing this—is it working?

Are you interested in studying that?

Sure [laughs]. But I need funding.

Isn't it possible some people just need less sleep?

There are people who are short sleepers. They could get five hours a night and that would be enough. One study just came out showing there is a genetic link with people who are short sleepers.

If you could sleep less, wouldn't that be better?

Yeah, yeah, sure [laughs]. But not if it's not good for you, right?

Have any cultures really nailed the optimal sleep schedule?

Japan is very, very good with napping. They honor people who take naps. They say, ‘These people must be working so hard that they're napping,' and they have nap hotels where you can just go for a short amount of time.

What's the worst culture for napping?

America is probably the worst culture in regard to sleep. People would say of all sacrifices, they would first sacrifice their sleep. There's also a very big stigma around napping.

So, the biggie. Why do we sleep?

Although the question of why do we sleep is completely unanswered, there's a lot of evidence that if you don't sleep, you're going to have problems. There's an increase in heart attacks when people are sleep-deprived, an increase in depression in people, or mood disorders in general. So clearly there must be some link to sleep and these physiological bases.

This is actually prime siesta time, according to your research. Shouldn't we be taking a nap now?

Right now, exactly!


Tia Ghose, a graduate student in the Science Communication Program at UC Santa Cruz, earned her bachelor's degree in mechanical engineering from the University of Texas at Austin and her master's degree in bioengineering from the University of Washington. She has worked as a reporting intern at the Salinas Californian and the science site of Wired.com. This summer, she will work as a Kaiser Family Foundation health reporting intern at the Milwaukee Journal-Sentinel.

© 2010 Tia Ghose