December 30, 2007

Night People vs. Morning People

At what time of the day do you concentrate best?

Night people and morning people tend to be found in different professions, with, say, musicians tending to be night people and business managers tending to be morning people. I'd never seen, however, any data on how the distribution of night and morning people differs by nationality or ethnicity.

I wonder how heritable it is? My guess would be that it's one of those traits, like handedness, that are only mildly heritable.

My supposition would be that this would be one of those traits you'd want widely widely varying among your relatives. In caveman days, when keeping a fire going could me a matter of life or death, you'd want some members of your clan to wake up early and be rarin' to go collect firewood and get the day started, while you'd want others who naturally stayed up late and made sure the fire didn't go out. But geneticists tend to scoff at my idea that there could be selection for variation.

The only evidence I've seen of national variations in night and morningness is in E.T. Bell's famous 1936 book Men of Mathematics: The Lives and Achievements of the Great Mathematicians from Zeno to Poincare. Bell, a fan of Sir Francis Galton, was interested in a lot of questions that are considered improper today. The chapter on Poincare discusses a 1902 survey of 100 mathematicians that asked them 30 questions about how they worked.
"Again, anyone with mathematical friends will have noticed that some like to work early in the morning ... while others do nothing till after dark. The replies on this point indicated a curious trend -- possibly significant, although there are numerous exceptions: mathematicians of the northern races prefer to work at night; while the Latins prefer the morning."

That's the reverse of the stereotype of Latins who stay up late because they take a siesta during the hot afternoons. Perhaps mathematicians tend to be out of sync with their societies?

My published articles are archived at -- Steve Sailer


Anonymous said...

I'm a night person but I often wish I weren't. The only way I can wake up early every morning is through sheer force of will, and then I generally end up feeling miserable for the first few hours of the day.

However, when I take hikes in the mountains, far from any lights or noise, it seems easier to sleep at night, and the heat of the sun wakes me up fairly early. That could be a side-effect from strenuous physical exertion.

Perhaps artificial lighting makes it easier for those of us who naturally would have gone to sleep only a little later in previous times to stay up all night. But I'm not sure -- the night sky can be spectacularly bright where there isn't any artificial lighting, and some of my favorite memories are of being under the stars in the wilderness.

I've been meaning to read this book on the topic.

Anonymous said...

I suppose "latin" here is to be taken in the older- and proper sense- of " Romance -speaking Southern Europeans": i.e., Frenchmen, Italians, Spaniards, ect, since you mention Poincaré.
Remember the times when "latin lovers" were the likes of Rodolfo Valentino and Maurice Chevalier, and not Eric Estrada?
In my experience, Latins in the above sense are usualy morning persons when it comes to intellectual pursuits, but become night people when socializing.
I don't know if the "siesta" has anything to do with it. There could be a cultural trait at work here.
Personally, I believe "siestas" are more widespread than acknowledged. After all, it's just a nap, which is pretty universal.

agnostic said...

There are many ways that genetic variation can be maintained, so don't listen to whoever these geneticists are. Remember what one of the reviewers at PNAS said about the human acceleration paper, doubting if selection ever happens. He's probably one of the smarter ones, too!

The day vs. night preference could be maintained by frequency dependence -- in a population full of morning people, a rare night person might have an advantage. The way it sounds, night people seem more introverted, so it may be mostly a question of what allows the rare introvert to invade a pop of extraverts.

And vice versa -- a rare extravert could invade a pop of introverts. They fill slightly different niches, so both are able to eke out a living, and at equilibrium there will be some fraction of each, and some variation will be due to genetic differences.

Re: caveman days, I think these morning vs. night preferences really became pronounced after the transition to agriculture -- agricultural people seem much more diverse phenotypically compared to HGs. It's like a division of labor emerging when the task is really complicated.

Jason Malloy said...

I'd never seen, however, any data on how the distribution of night and morning people differs by nationality or ethnicity.

A comparison of morning–evening orientation in 6 countries reported:

"... mean differences were found across countries, suggesting that people in more temperate climates perceive themselves to be more morning-oriented than their peers in less temperate climates."

Another study comparing German and Spanish students found 'morningness' and 'morning alertness' were higher in the German students.

Some studies comparing different races within countries found fewer differences.

A study in New Zealand found no ethnic differences.

A comparison of Hispanic, white, Asian, and black students in the US found small significant differences for adolescents. Hispanics were higher in morningness than whites and blacks, and Asians higher than blacks.

I wonder how heritable it is? My guess would be that it's one of those traits, like handedness, that are only mildly heritable.

A study by Thomas Bouchard using 205 pairs of reared together twins, and 105 reared apart twins:

"... showed that genetic variability accounted for about 54% of the total variance in morningness-eveningness; age contributed to 3% of the variance; and the remaining variance was explained by nonshared environmental influences and measurement error. Shared rearing environmental effects were not significant."

Perhaps mathematicians tend to be out of sync with their societies?

Evening types apparently have higher IQ scores, but assuming the data is from North America, perhaps it's opposite in less temperate places.

Anonymous said...

Just throwing something out here, but I wonder if general mood has anything to do with it. I'm a person who's suffered from a mild form of bipolar disorder for most of my life - since before puberty. I'm also very much a night person. I find the nighttime more relaxing, and if I've been in a good mood during the day I want to continue that as long as reasonably possible. I've got physical and creative energy I can't always count on.

I pay for it in the morning, of course, so there's probably a bit of a vicious circle going on there.

I recall hearing about studies that link night people to higher rates of heart disease and shorter lifespans. Those things are also linked with depression.

Do people who go on anti-despressants like SSRIs tend to alter their sleeping habits, and if so is it a result of mood changes? Do people who start exercising do so? And are the effects of exercise physical (people who exercise tend to get better sleep), or related to improvements in mood?

Anonymous said...

I'm a night person, and so is my father. If our schedules were entirely unconstrained, we'd both prefer to wake up around noon and go to sleep around 4 am -- which is only an hour before my morning-person mother likes to wake up. My father and I both greatly enjoy math and use lots of it in our jobs, while my mother pretty much stopped taking or using math after getting a D in geometry in 9th grade. We're all descended from northern Europeans.

Anonymous said...

Selection for variation of the sort you refer to requires group selection, the notion of which was for a time considered improper to speak of. I think the recent paper by Wilson and Wilson should have redeemed it, so I suggest you feel more confident in your idea. I think it's perfectly plausible.

Anonymous said...

It's too hard to tell whether someone is "naturally' a lark or an owl. All the homeschooling families I know tend towards larkism or owlism as a group, but if you've got to send the children to school, then you've got to get up in the morning. The benefits of doing so may outweigh one's innate tendency later in life - or a natural lark may be so harmed by being required to do without sufficient sleep during puberty that their circadian rhythms are permanently messed up.

Anonymous said...

Oh, and any mother can explain that northern-southern European disparity. The mathematicians were tending towards work times when no one else was awake to bother them - the Latins because everyone was sleeping off the night before, the northerners because everyone was early to bed.

Anonymous said...

Utterly the worst period of my life were 18 months on the graveyard shift in a post-production facility. I stumbled thru life in a fog, up all night, only fitful non-restorative sleep during the day. We never could get decent help on that shift, either. "Normal" people would come in all gung ho but then you would see it just slowly grind them down. One night our boss went out for "lunch" (3 a.m.) and just never came back. I finally bailed out on it myself without even another job lined up to go to. Just couldn't do it anymore. No wonder I was never good at math.

Equally interesting is the sacred concept of 8 hours of uninterrupted sleep. This seems to be a modern invention. From old diaries we learn that people in previous eras went to bed early, slept a few hours, got up for a while to tend the fire or make sure the livestock were safe, back to bed for a few hours, up again to break the ice in the cistern, back to bed, etc, etc. If you slept for 8 straight hours, you were probably sick.

Anonymous said...

I'm English-Irish by stock, and do my best work after 8 PM. The day is for pothering about, getting haircuts, wages, and assorted grief and packing victuals and toiletries.

Night time is generally quieter! Who can rationate in the roar of day? Even daylight itself seems loud to me. I sympathize with Mr. Burns of The Simpsons, who said, "Since the beginning of time, man has yearned to destroy the sun."

Anonymous said...

I'm waiting for my earlier comment to post but it's almost 11 and Steve still ain't up yet...

Anonymous said...

I suspect most of these "Latins" were Italians as the citation was from 1936 and I have heard the term used that way before.

Anonymous said...

I'm from Corsica (Southern France) and all my relatives but one wake up early. In summer time, you have to wake up very early because at 10:00am it is already too hot outdoors to work efficiently. In Latin places, the least productive hours are between 10:00am and 5:00pm.

Anonymous said...

So the Latin mathematicians like to work in the day,the Nordics at night. Hmmm...what do the Latins do at night? My guess is gettin' busy doing a different kind of math:multiplication! They love the ladies! -Josh

Anonymous said...

Traditional Hispanic schedules incorporate a big meal and rest time (the siesta, of course) in the afternoon. They start work at "normal" times, but they eat dinner - usually lighter than the midday meal - very late and stay up later than Northern Europeans typically do. In other words, they keep more or less the schedule stephent describes.

In Buenos Aires, which, granted, is sort of an extreme example, restaurants are empty until 9 p.m., and bars and clubs don't start jumping until midnight, even on weeknights. And yet, businesses open at "normal" hours. This seems a quite civilized schedule to me, as it allows for productive periods for both morning and night people and does not make work the centerpiece of the day. But, then again, I am both lazy and a night person, so my views are suspect in modern, workaholic America.

Anyway, the traditional Hispanic schedule is to some extent being swept away. I know that Mexico, for example, is mostly on "gringo time" these days, at least in Mexico City, because of longer commutes and a need to conform to international business practices.

Anonymous said...

I prefer the reduced sensory input of nights. A lamp light or a computer monitor is all I need. Little light and no noise is ideal. I feel mentally cloudy until around 6pm-7pm or so. Right now, my schedule doesn't fully allow sleep patterns conducive to my night habits. :-(

Anonymous said...

Equally interesting is the sacred concept of 8 hours of uninterrupted sleep. This seems to be a modern invention. From old diaries we learn that people in previous eras went to bed early, slept a few hours, got up for a while to tend the fire or make sure the livestock were safe, back to bed for a few hours, up again to break the ice in the cistern, back to bed, etc, etc. If you slept for 8 straight hours, you were probably sick.

No one can count the ways our biological preferences have been screwed up by modernity. The switch from the farm to the factory, I suspect, changed a lot. So too the switch from small towns to ever larger ones; and then the move from cities to suburbs.

Every one of these has exacted a toll on the broken up day we traditionally enjoyed. Extended lunches in Spain and Germany are diasappearing as people find handling a 4x daily commute simply unreasonable.

Anonymous said...

But geneticists tend to scoff at my idea that there could be selection for variation.

Which genecists? Diversifying/disruptive selection is an established phenomenon...

agnostic said...

Mrs. Anonymous' guess is close -- but that suggests that mathematicians are choosing to be morning or night people based on the local average. But it seems like something that you can't control (it's moderately heritable).

That, as well as many other clues, suggests that mathematicians (and scientists) are misfits -- smart and hardworking, but who due to other traits beyond their control don't really fit in with the smart and hardworking people who run society, and so who need to be protected by royal patronage, taxpayer-generated grants, and so on.

Anonymous said...

Don't you think light exposure has something to do with it? The last place I lived, my room was flooded with sunlight every morning making it impossible to sleep in. Where I live now, I have a harder time getting up early. I'm certain this is because I use curtains to insulate from the cold. The room is also shielded from sunlight. There's also the fact that when I visited the UK I became a lark counter to my natural tendencies due to the relatively extended hours of daylight compared to the US.

I seem to remember an article on insomnia that suggested spending at least 2 hours a day in bright light in order to maintain circadian rhythms. All this leads me to conclude that there may be many factors determining sleep/wake patterns not just a gene for getting up early or staying up late. I can't imagine what I'd do during 6 months of darkness other than sleep 12 - 14 hrs at a time.

James said...

I think my "day" is 26 hours so that I tend to stay up two hours later on consecutive nights until my bedtime is something ridiculous at which point I'll start forcing myself to sleep early enough that I'm able to wake up in time the next morning. When I don't have a job or school I'll cycle through the entire day with wake times shifting two hours later after every sleep. Asleep at 2am, 4am, 6am, 8am, 10am, etc.

When I was in high school I thought my sleeping habits were due primarily to being a lazy procrastinator; I put my homework off until there was nothing else to do.

Anonymous said...

I'm a night person doing evrything including math at night. The reason is simple: it's the time when everybody finally shuts the hell up, the whole city goes to sleep so there are no distractions, and I can finally concentrate.


Anonymous said...

I thought I was the only person under the age of 60 who had read "Men of Mathematics: The Lives and Achievements of the Great Mathematicians from Zeno to Poincare."

And, yes, it is a truly great book.

One small observation I have had as a Computer Programmer is that many programmers are night people. It is something of a stereotype that your average Java/Linux/C++ Geek doesnt start focusing until after dark.

Anonymous said...

I get up super-early in the morning (~3-4am) and go to bed around 8-9pm. I get a lot done in the early morning hours, because the rest of my family is asleep. I don't use an alarm clock, and I've always gotten up early since childhood. I had some weird patterns in college, going to bed early, getting up at 2am to do stuff with friends, and that sort of thing. I do my best writing around 5am.

Likewise, my husband stays up later than the rest of us, as he can get stuff done when the rest of us are asleep.

Both my husband and I are from British Isles background (mostly Scottish and Irish). We both grew up in the South, and learned to avoid doing anything particularly vigorous mid-day. We live in NY now.

Anonymous said...

I fit Poincare's findings for Latins, though I am a physicist. Theoretical condensed matter is pretty mathy anyway. My ancestry is primarily Spanish (3/4) with a large Amerindian component (1/4).
I wake up between 5-6 am and my brain is mush by 5 pm. My parents are both morning people, though not as much as I am. Most of the people in my field tend to be night people. The only other morning person in my group is a Brahmin Indian. The morning preference probably isn't cultural in me; I rejected Hispanic culture when I was very young. The only aspect of the culture I embrace is womanizing.

Sally said...

I am more of a night person; my natural circadian rhythm is to wake up around 9 AM and to go to bed around 2 AM. Unfortunately, I have to force myself to rise at 6:30 AM in order to conform to the rest of society (thank God for strong coffee). But left to my own devices, I would spend my mornings in an unproductive stupor, and start really cranking and getting things done in the afternoon well into the night.

I'm a mutt ethnically (Hungarian, English, Scottish, German, Irish, French, with a bit of Cherokee and Choctaw). My dad was a lark, my mom and brother and I were owls. My husband is an owl, and our kids are young but seem to have owlish tendencies (i.e., they get more revved up and energetic as the day goes on, and settling them down for bed can be quite a task).

We also have a lot of ADHD and giftedness in the family; and ADHD people tend to be night owls. Hard to wake up, hard to settle down.