New research shows that a full night's rest recharges the brain and boosts memory, attention span-even creativity!
SARAH GROTH HAD only two more weeks before her trip to Israel, and if things kept going as they were, she was going to have trouble asking locals how to find the restroom. Although she stayed up late each night studying phrases, and got up early the next morning to cram some more, by the next day it always seemed she was back where she started- hardly past "shalom," let alone to "Kamah zeh o'leh?" ("How much does this cost?"). When Sarah, 25, told a psychology student friend about her problems, however, he surprised her. He didn't suggest a new way to lodge tourist phrases into her head or even recommend an iPhone app for it. Instead, he suggested she get more than the six hours of sleep she had been allowing herself while she was cramming for the trip.
It worked. Within a week, Sarah was back to her normal seven-and-ahalf hours of sleep, and suddenly "Eifo ha'sherutim?" ("Where is the bathroom?") was rolling off her tongue. Sarah had unwittingly replicated, on a very small scale, a growing number of experiments showing that sleep is a powerful force for consolidating memories (making them stick), not to mention other cognitive functions as diverse as creative thinking and split-second decision making. "Attention, executive function, judgment- they're all impaired by a lack of sleep," says psychologist Howard Nusbaum of the University of Chicago.
Emerging research is finally shedding much-needed light on a longstanding mystery: Why do humans spend about one-third of our lives catching z's? Over the years, scientists have speculated that sleep might promote wound healing, conserve energy, recharge the immune system, or simply (no kidding!) be nature's way of preventing us from walking around after dark and getting eaten by lions. While most of those theories have fallen by the wayside, the idea that sleep promotes some aspects of physical health has held up; insufficient sleep can indeed cause cardiovascular disease, diabetes, and obesity (see sidebar on the next page). Given that sleep is a brain state, it makes sense that it affects the brain- and not just in causing it to generate the bizarre narratives we call dreams.
The new discoveries about the cognitive function of sleep make our nation's collective failure to get enough shut-eye even more alarming. In a poll released by the National Sleep Foundation in March, 43 percent of Americans between 13 and 64 said they rarely get a good night's sleep on weeknights (when they can't sleep late the next morning); 60 percent said they experience a sleep problem such as waking in the night every or almost every night. Most say they need about seven and a half hours of sleep to feel their best- in line with expert advice that adults get between seven and eight hours- but report getting, on average, six hours and 55 minutes. About 15 percent of adults under 65 say they sleep less than six hours on weeknights. Among the sleep-deprived who have jobs, 74 percent of those over 30 said drowsiness impairs their work. It's amazing more of us aren't using toothpicks to prop up our eyelids.
Many studies- not to mention personal experience- have shown that sleep impairs brain function in a way not too different from being slightly tipsy. In a 2009 study, psychologist Todd Maddox of the University of Texas and colleagues found that sleep acts even more specifically: It gives us the ability to make the kind of split-second responses that firefighters, police officers, physicians, and others often need to make. But when people are sleep deprived, as members of these professions often are, they shift from a split-second, gut-level process of categorizing information to a slower, rule-based process- the difference between going with your gut and trying to reason something out. When the decision comes in an area in which you are an expert, and where gut-level decisions are more accurate, this switch can have tragic consequences. …