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Study the history of time—from the first sundials in ancient Egypt to the early mechanical clocks of sixteenth-century Europe to the advent of time zones in the nineteenth century—and you’ll soon realize that much of what we assume are “natural” units of time are really fences our ancestors constructed in order to corral time.
Positive affect—language revealing that tweeters felt active, engaged, and hopeful—generally rose in the morning, plummeted in the afternoon, and climbed back up again in the early evening.
When the researchers crunched the numbers, they found a “consistent and strong bimodal pattern”—twin peaks—during the day. The women’s positive affect climbed in the morning hours until it reached an “optimal emotional point” around midday. Then their good mood quickly plummeted and stayed low throughout the afternoon only to rise again in the early evening.7
“[A]n important takeaway from our study for corporate executives is that communications with investors, and probably other critical managerial decisions and negotiations, should be conducted earlier in the day.”11
In 1983 Daniel Kahneman, he of Nobel Prize and DRM fame, and his late collaborator, Amos Tversky, introduced the Linda problem to illustrate what’s called the “conjunction fallacy,” one of the many ways our reasoning goes awry.12
First, our cognitive abilities do not remain static over the course of a day. During the sixteen or so hours we’re awake, they change—often in a regular, foreseeable manner. We are smarter, faster, dimmer, slower, more creative, and less creative in some parts of the day than others.
Second, these daily fluctuations are more extreme than we realize. “[T]he performance change between the daily high point and the daily low point can be equivalent to the effect on performance of drinking the legal limit of alcohol,” according to Russell Foster, a neuroscientist and chronobiologist at the University of Oxford.15 Other research has shown that time-of-day effects can explain 20 percent of the variance in human performance on cognitive undertakings.16
Third, how we do depends on what we’re doing. “Perhaps the main conclusion to be drawn from studies on the effects of time of day on performance,” says British psychologist Simon Folkard, “is that the best time to perform a particular task depends on the nature of that task.” The Linda problem is an analytic task. It’s tricky, to be sure. But it doesn’t require any special creativity or acumen. It has a single correct answer—and you can reach it via logic. Ample evidence has shown that adults perform best on this sort of thinking during the mornings. When we wake up, our body temperature
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Alertness and energy levels, which climb in the morning and reach their apex around noon, tend to plummet during the afternoons.18 And with that drop comes a corresponding fall in our ability to remain focused and constrain our inhibitions.
“having math in the first two periods of the school day instead of the last two periods increases the math GPA of students”
Ernesto is a dealer in antique coins. One day someone brings him a beautiful bronze coin. The coin has an emperor’s head on one side and the date 544 BC stamped on the other. Ernesto examines the coin—but instead of buying it, he calls the police. Why?
The answer goes back to those sentries guarding our cognitive castle. For most of us, mornings are when those guards are on alert, ready to repel any invaders. Such vigilance—often called “inhibitory control”—helps our brains to solve analytic problems by keeping out distractions.22 But insight problems are different. They require less vigilance and fewer inhibitions. That “flash of illuminance” is more likely to occur when the guards are gone. At those looser moments, a few distractions can help us spot connections we might have missed when our filters were tighter. For analytic problems,
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Some have called this phenomenon the “inspiration paradox”—the idea that “innovation and creativity are greatest when we are not at our best, at least with respect to our circadian rhythms.”23 And just as the studies of school performance in Denmark and Los Angeles suggest that students would fare better taking analytic subjects such as math in the morning, Wieth and Zacks say their work “suggests that students designing their class schedules might perform best in classes such as art and creative writing during their non-optimal compared to optimal time of day.”
In short, our moods and performance oscillate during the day. For most of us, mood follows a common pattern: a peak, a trough, and a rebound.
And that helps shape a dual pattern of performance. In the mornings, during the peak, most of us excel at Linda problems—analytic work that requires sharpness, vigilance, and focus. Later in the day, during the recovery, most of us do better on coin problems—insight work that requires less inhibition and resolve. (Midday troughs are good for very little, as I’ll explain in the next chapter.) We are like mobile versions of de Mairan’s plant. Our capacities open and close according to a clock we don’t control.
The Edisons among us are late chronotypes. They wake long after sunrise, detest mornings, and don’t begin peaking until late afternoon or early evening. Others of us are early chronotypes. They rise easily and feel energized during the day but wear out by evening. Some of us are owls; others of us are larks.
Chronotypes are like feet in another way, too. There’s not much we can do about their size or shape. Genetics explains at least half the variability in chronotype, suggesting that larks and owls are born, not made.29 In fact, the when of one’s birth plays a surprisingly powerful role. People born in the fall and winter are more likely to be larks; people born in the spring and summer are more likely to be owls.
After genetics, the most important factor in one’s chronotype is age. As parents know and lament, young children are generally larks. They wake up early, buzz around throughout the day, but don’t last very long beyond the early evening. Around puberty, those larks begin morphing into owls. They wake up later—at least on free days—gain energy during the late afternoon and evening, and fall asleep well after their parents. By some estimates, teenagers’ midpoint of sleep is 6 a.m. or even 7 a.m., not exactly in synch with most high school start times. They reach their peak owliness around age
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The chronotypes of men and women also differ, especially in the first halves of their lives. Men tend toward eveningness, women toward morningness. However, those sex differences begin to disappear around the age of fifty.
Let’s begin with personality, including what social scientists call the “Big Five” traits—openness, conscientiousness, extraversion, agreeableness, and neuroticism. Much of the research shows morning people to be pleasant, productive folks—“introverted, conscientious, agreeable, persistent, and emotionally stable” women and men who take initiative, suppress ugly impulses, and plan for the future.33 Morning types also tend to be high in positive affect—that is, many are as happy as larks.
Owls, meanwhile, display some darker tendencies. They’re more open and extroverted than larks. But they’re also more neurotic—and are often impulsive, sensation-seeking, live-for-the-moment hedonists.
The problem is that our corporate, government, and education cultures are configured for the 75 or 80 percent of people who are larks or third birds. Owls are like left-handers in a right-handed world—forced to use scissors and writing desks and catcher’s mitts designed for others. How they respond is the final piece of the puzzle in divining the rhythms of the day.
Synchrony even affects our ethical behavior. In 2014 two scholars identified what they dubbed the “morning morality effect,” which showed that people are less likely to lie and cheat on tasks in the morning than they are later in the day. But subsequent research found that one explanation for the effect is simply that most people are morning or intermediate chronotypes. Factor in owliness and the effect is more nuanced. Yes, early risers display the morning morality effect. But night owls are more ethical at night than in the morning. “[T]he fit between a person’s chronotype and the time of
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For example, if you’re a larkish lawyer drafting a brief, do your research and writing fairly early in the morning. If you’re an owlish software engineer, shift your less essential tasks to the morning and begin your most important ones in the late afternoon and into the evening. If you’re assembling a brainstorming group, go for the late afternoon since most of your team members are likely to be third birds. Once you know your type and task, it’s easier to figure out the time.
Even if you can’t control the big things, you might still be able to shape the little things. If you’re a lark or a third bird and happen to have a free hour in the morning, don’t fritter it away on e-mail. Spend those sixty minutes doing your most important work.
Lose weight: When we first wake up, having not eaten for at least eight hours, our blood sugar is low. Since we need blood sugar to fuel a run, morning exercise will use the fat stored in our tissues to supply the energy we need. (When we exercise after eating, we use the energy from the food we’ve just consumed.) In many cases, morning exercise may burn 20 percent more fat than later, post-food workouts.1 Boost mood: Cardio workouts—swimming, running, even walking the dog—can elevate mood. When we exercise in the morning, we enjoy these effects all day. If you wait to exercise until the
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Enjoy the workout a bit more: People typically perceive that they’re exerting themselves a little less in the afternoon even if they’re doing exactly the same exercise routine as in the morning.6 This suggests that afternoons may make workouts a little less taxing on the mind and soul.
Drink a glass of water when you wake up. How often during a day do you go eight hours without drinking anything at all? Yet that’s what it’s like for most of us overnight. Between the water we exhale and the water that evaporates from our skin, not to mention a trip or two to the bathroom, we wake up mildly dehydrated. Throw back a glass of water first thing to rehydrate, control early morning hunger pangs, and help you wake up.
Don’t drink coffee immediately after you wake up. The moment we awaken, our bodies begin producing cortisol, a stress hormone that kick-starts our groggy souls. But it turns out that caffeine interferes with the production of cortisol—so starting the day immediately with a cup of coffee barely boosts our wakefulness. Worse, early-morning coffee increases our tolerance for caffeine, which means we must gulp ever more to obtain its benefits. The better approach is to drink that first cup an hour or ninety minutes after waking up, once our cortisol production has peaked and the caffeine can do
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Soak up the morning sun. If you feel sluggish in the morning, get as much sunlight as you can. The sun, unlike most lightbulbs, emits light that covers a wide swath of the color spectrum. When these extra wavelengths hit your eyes, they signal your brain to stop producing sleep hormones and start producing alertness hormones.
Schedule talk-therapy appointments for the morning. Research in the emerging field of psychoneuroendocrinology has shown that therapy sessions may be most effective in the morning.8 The reason goes back to cortisol. Yes, it’s a stress hormone. But it also enhances learning. During therapy sessions in the morning, when cortisol levels are highest, patients are more focused and absorb advice more deeply.
When the Danish students had a twenty- to thirty-minute break “to eat, play, and chat” before a test, their scores did not decline. In fact, they increased. As the researchers note, “A break causes an improvement that is larger than the hourly deterioration.”
“[F]irst, cognitive fatigue should be taken into consideration when deciding on the length of the school day and the frequency and duration of breaks.
(Another study of U.S. federal courts found that on the Mondays after the switch to Daylight Saving Time, when people on average lose roughly forty minutes of sleep, judges rendered prison sentences that were about 5 percent longer than the ones they handed down on typical Mondays.
One problem with afternoons is that if we stick with a task too long, we lose sight of the goal we’re trying to achieve, a process known as “habituation.” Short breaks from a task can prevent habituation, help us maintain focus, and reactivate our commitment to a goal.
High performers, its research concludes, work for fifty-two minutes and then break for seventeen minutes.
One study showed that hourly five-minute walking breaks boosted energy levels, sharpened focus, and “improved mood throughout the day and reduced feelings of fatigue in the late afternoon.”
These “microbursts of activity,” as the researchers call them, were also more effective than a single thirty-minute walking break—so much so that the researchers suggest that organizations “introduce physically active breaks during the workday routine.”
But much of the research on restorative breaks points toward the greater power of being with others, particularly when we’re free to choose with whom we spend the time.
research in South Korean workplaces shows that social breaks—talking with coworkers about something other than work—are more effective at reducing stress and improving mood than either cognitive breaks (answering e-mail) or nutrition breaks (getting a snack).
Nature breaks may replenish us the most.24 Being close to trees, plants, rivers, and streams is a powerful mental restorative, one whose potency most of us don’t appreciate.
By now, it’s well known that 99 percent of us cannot multitask.
Vigilance breaks and restorative breaks offer us a chance to recharge and replenish, whether we’re performing surgery or proofreading advertising copy.
It’s also a guardrail for our metabolism; eating breakfast restrains us from gorging the rest of the day, which keeps our weight down and our cholesterol in check.
The non–desk lunchers were better able to contend with workplace stress and showed less exhaustion and greater vigor not just during the remainder of the day but also a full one year later.
The most powerful lunch breaks have two key ingredients—autonomy and detachment.
Longer lunch breaks and lunch breaks away from the office can be prophylactic against afternoon peril.
Done right, naps can be a shrewd response to the trough and a valuable break.
An afternoon nap expands the brain’s capacity to learn, according to a University of California–Berkeley study. Nappers easily outperformed non-nappers on their ability to retain information.
“Even for individuals who generally get the sleep they need on a nightly basis, napping may lead to considerable benefits in terms of mood, alertness and cognitive performance. . .
