Night owl vs early bird: is being a night owl genetic?

A night owl is someone whose energy only really arrives after the evening begins and who, on days off, naturally sleeps and wakes late; sleep research calls this an evening chronotype. The early bird, or morning type, sits at the other end of the spectrum. Being a night owl has an inborn component, but it is not fixed for life: age, daylight and routine all push the body clock earlier or later. As for the idea that night owls are smarter, the link does exist in the research, but it is very small.

What is a night owl? Early birds, morning types and evening types share one spectrum

Night owls and early birds are opposite ends of one ruler, and the ruler is called chronotype: where your body clock sits against the 24-hour day.

The names first. Night owl, evening type and evening person all describe the late end; early bird, morning type, morning person and lark describe the early end; in between are intermediate types. “Night owl” and “early bird” are figures of speech borrowed from birds: owls are active after dark, and the early bird gets the worm. Researchers use “lark” and “owl” too, so a lark and an early bird are the same thing.

Researchers use two main tools to place a chronotype. One is the Morningness-Eveningness Questionnaire (MEQ), which asks when you prefer to wake and when you work best. The other is the Munich Chronotype Questionnaire (MCTQ) from Roenneberg and colleagues (2003), which asks when you sleep and wake on workdays and days off and uses the sleep midpoint on free days as the chronotype marker. Both questionnaires are copyrighted, so we do not reproduce them.

Chronotype is spread like a hill: most people in the middle, fewer toward each end. Fischer and colleagues (2017) computed chronotype from the weekend sleep midpoints of 53,689 people in a US time-use survey and found a roughly normal distribution overall and within every age group. Roenneberg and colleagues (2004), with about 25,000 people, likewise found extremely early and extremely late people to be rare. Because it is a continuous spectrum, “what share of people are morning types” depends on where you draw the cutoff, which is why the numbers online contradict each other.

Popular books also sort sleepers into animals such as bear, lion, wolf and dolphin; that is individual authors’ labeling, and research has no standard version of it. Our five sleep animals are our own design too.

Are night owls born that way? Genes, age and daylight each play a part

Being a night owl has an inborn basis, but the clock shifts with age and is steered by daylight, so “inborn” does not mean “fixed.”

Start with genes. Jones and colleagues (2019) analyzed data from 697,828 people in the UK Biobank and the genetic testing company 23andMe and raised the number of known variants linked to being a morning person from 24 to 351. The same study used wrist-worn activity data on 85,760 people: the 5% carrying the most morning-leaning variants and the 5% carrying the fewest differed in sleep timing by only 25 minutes on average. Genes do push, but every variant found so far pushes very gently, and together they do not explain all the variation.

Then age. Roenneberg and colleagues (2004) show that children are early types, get steadily later through puberty, reach their latest at about age 20 and then move earlier year after year. Women peak at around 19.5 and men keep getting later until about 20.9, which is why men average later than women through most of adult life until the gap closes around 50. Fischer and colleagues (2017) also saw the latest point near age 19 in the US sample. The dorm hallway still lit up at 2 a.m. and the retirees walking the park at 5:30 are partly a clock written into the body by age. For a check on how old you feel inside, see How accurate is a mental age test?; the age of your body clock shows in when you wake on a day off.

Daylight is the third force. Roenneberg and colleagues (2003) analyzed 500 questionnaires and found that the more time people spent outdoors in daylight, the earlier they slept. The camping experiment of Wright and colleagues (2013) made this concrete: eight participants (six men and two women, average age 30) lived normally for a week, then camped for a week in the Colorado mountains with only sunlight and campfires, no flashlights and no phones. Their biological night, when melatonin begins to rise, came about two hours earlier after camping than in ordinary life, and the later someone started, the more they shifted.

So the claim in some articles that night owls can never become early risers does not fit these studies. What researchers suggest is that your relative position among people of your age and sex probably stays with you for life (Roenneberg et al., 2004), while the absolute clock time can move.

Social jet lag: what really wears night owls out is Monday morning

The hardest part of being a night owl is being pulled earlier by an alarm on workdays and then snapping back to your own schedule on days off; the round trip is called social jet lag.

Wittmann and colleagues (2006) define it this way: however much your sleep timing differs between free days and workdays is like a time-zone trip your body takes every week. Roenneberg and colleagues (2003) also observed that the later the chronotype, the more sleep debt builds up on workdays, to be repaid with several extra hours on days off. Friday night energy and a Monday-morning commute where you doze standing up are often exactly this round trip.

The arithmetic is simple. Take the midpoint between falling asleep and waking, then compare workdays with days off. Take Sam, who works a 9 a.m. start:

Sam sleeps 6.5 hours on workdays and 8.5 on days off, and the two midpoints sit 2 hours 15 minutes apart, like flying a two-hour time-zone trip every weekend and flying back. We entered Sam’s full set of answers into the scoring program of our Sleep Animal Quiz (beyond the four times above, the other answers lean late, such as hitting snooze and being the first to suggest late-night tacos). The result is The Midnight Owl, with The Afternoon Koala as the second-closest animal, an energy peak around 10 p.m. and social jet lag of 2.25 hours (the report works in half-hour steps and shows about 2.5 hours).

Now change just two answers: on days off, fall asleep between 12:30 and 1:30 and wake between 8:30 and 10:00, leaving everything else alone. Sam is still a Midnight Owl, but social jet lag drops to about 1 hour (52.5 minutes exactly). The small experiment shows two things. Social jet lag and your type can be read separately, and to ease Monday you can start with the weekend wake-up time instead of fighting your own constitution. This is a simplified calculation; the MCTQ used in research also corrects for sleep debt, and the quiz’s clock questions offer time ranges, with the scoring taking a representative hour for each range.

Our Chronotype Quiz: What's Your Sleep Animal? has 20 questions. Four clock questions ask when you sleep and wake on workdays and days off, which feeds the social jet lag figure, and the two days-off questions also count toward chronotype. The other 16 measure four traits: chronotype (morning to night), warm-up speed (how fast you come online after waking), rhythm flexibility (how well you cope when your schedule is disrupted) and sleep need (how full a night you require), with chronotype double weighted. The four scores map to five sleep animals:

The Dusk Hedgehog and the Midnight Owl both lean late, and the difference is flexibility: the Hedgehog is a regular who runs a little later and struggles when the routine breaks, while the Owl handles both late nights and catch-up sleep, which is also why the clock tends to drift later. The report draws a daily energy curve from your answers and slots in times for focus, meetings, exercise and winding down. It is a self-observation tool, not a sleep test.

Staying up late does not always make a night owl: evening type, revenge bedtime procrastination and delayed sleep phase

The same 2 a.m. bedtime can mean an evening-leaning constitution, a reluctance to end the day known as revenge bedtime procrastination, or, less often, delayed sleep-wake phase disorder that needs medical attention; the clue lies in days off with no alarm.

Revenge bedtime procrastination is closest to what research calls bedtime procrastination. Kroese and colleagues (2014) define it as failing to go to bed at the intended time with no external reason stopping you. In a survey of 177 people they found that the weaker a person’s self-regulation, the more often they procrastinated at bedtime, and that bedtime procrastination was linked to not getting enough sleep. The typical American scene: you work until 7 p.m., get home and finish dinner, and by 10 you finally have time that belongs to you, so you scroll Instagram, binge a show and answer the group chat until 2, though you have been yawning since midnight. The problem there usually lies in a day that was filled up entirely, not in the body clock.

Delayed sleep-wake phase disorder is a diagnosis in sleep medicine. According to the American Academy of Sleep Medicine’s patient education pages, sleep timing is two or more hours later than conventional times and stays stably delayed; people cannot fall asleep at the desired time or wake in the morning, yet when they sleep on their own schedule the length and quality of sleep are normal. It is more common in teens and young adults, with estimates of roughly 7% to 16%, and is easily mistaken for insomnia.

The three can overlap. A naturally late person who also does revenge bedtime procrastination after work will find the clock pushed even later; dealing with the “sleepy but not sleeping” stretch first is often easier than taking on early waking straight away.

Are night owls smarter and early birds more disciplined? The real numbers

Both claims leave some trace in research, but the associations are small and almost useless for judging any one person.

“Night owls are smarter” is the most quoted. The meta-analysis by Preckel and colleagues (2011) combined multiple studies and found that the more evening-leaning people were, the slightly higher their cognitive ability scores (r = .08) but the slightly lower their academic achievement (r = −.14). The more morning-leaning, the slightly higher the achievement (r = .16), with almost no difference in cognitive ability (r = −.04). What does r = .08 mean? Chronotype explains under 1% of the individual differences in cognitive scores, an effect visible only when data from over a thousand people are pooled and barely noticeable between you and the coworker at the next desk. One plausible reading is that classes and exams are mostly scheduled in the morning, so morning students take them at their own best time.

The evidence for “early birds are more disciplined” is a little stronger. Tsaousis (2010) combined 35 samples and 8,589 people and found that the more morning-leaning, the higher the conscientiousness (r = .29) and slightly higher the agreeableness (r = .13), while openness (−.09), extraversion (−.06) and neuroticism (−.07) showed almost no link. This is correlation and cannot show direction: disciplined people may find it easier to keep a regular schedule, or early risers may simply fit the social timetable better and so look more “disciplined.” For what conscientiousness means in personality research, see What are the Big Five personality traits?.

The last row deserves a word: being a night owl and being an extravert are not the same thing. Someone wide awake at midnight may be quietly coding or drawing alone. For introversion and extraversion themselves, there is What do introvert and extrovert mean?.

Is being a night owl unhealthy? How to read the big studies

Large studies do find that evening type goes with some health risks, but the increases are modest and mostly explained by smoking, sleep and activity, all of which you can change yourself.

Searching “night owl” tends to surface news about a cardiovascular study. The original is Kianersi and colleagues (2026): they followed 322,777 UK Biobank adults aged 39 to 74 who began without cardiovascular disease, for a median of 13.8 years. Compared with intermediate types, people who described themselves as definitely evening types had about 16% higher risk of heart disease or stroke, and a 79% higher share with poor scores on the American Heart Association’s Life’s Essential 8 (diet, physical activity, nicotine exposure, sleep, weight, blood lipids, blood glucose and blood pressure). Breaking it down further, about 75% of the link between evening type and cardiovascular disease could be explained by those eight health measures. The authors conclude that evening types may benefit especially from improving those risk factors.

An earlier study, Knutson and von Schantz (2018), analyzed 433,268 people from the same database over an average 6.5 years and, after adjusting for smoking, weight, sleep length and other factors, found all-cause mortality about 10% higher in definite evening types than in definite morning types. The authors suggest that possible reasons include lifestyle and a long-term mismatch between the internal clock and work or school hours.

Three points help when reading this kind of research:

• They are observational. They show that evening type and these outcomes appear together; they cannot prove that staying up late itself causes disease.
• Risk ratios are relative. 10% higher means that if 2 in 100 people in the morning group die over some period, about 2.2 in 100 in the evening group do, not 1 in 10 night owls.
• Misalignment may matter more than lateness. Wittmann and colleagues (2006) found that the strongest link between lateness and smoking probably came through social jet lag, and Roenneberg and colleagues (2012) found that beyond sleep length, bigger social jet lag went with higher BMI.

In terms of what to do: the consensus statement of the American Academy of Sleep Medicine and the Sleep Research Society says adults should regularly sleep 7 or more hours a night (Watson et al., 2015); add a fixed wake time, daytime light, little smoking or drinking and regular exercise. A night owl who looks after these on their own rhythm is being far more realistic than one who fights the alarm daily.

Can a night owl become an early bird? The three-week trial and a workweek version

A night owl can move the clock one to two hours earlier, mostly through light and a fixed routine rather than willpower, but the new schedule has to be kept up or the clock may slowly drift back.

The most cited trial is Facer-Childs and colleagues (2019). Twenty-two healthy night owls, who on average slept at 2:30 a.m. and woke at 10:15 a.m., were randomly split into two groups. The 12 in the intervention group lived by a set of rules for three weeks: wake and bed times 2 to 3 hours earlier than usual, outdoor light in the morning, less light at night, the same schedule on workdays and days off, breakfast soon after waking, lunch at a fixed time, no dinner after 7 p.m., no caffeine after 3 p.m., and exercise moved to the morning for those who exercised. The other 10 were a control group told only to eat lunch at a fixed time. After three weeks the intervention group’s sleep timing had moved about two hours earlier with no loss of sleep time; self-rated depression and stress dropped, and morning reaction time and grip strength improved.

A week of practice for night owls (workweek version)

The principles from the trial can be turned into a workweek like this. Moving only about 15 minutes a week is the advice our Sleep Animal Quiz report gives the Midnight Owl, and it is easier to sustain than moving two hours at once:

1. Fix the wake time, not the bedtime. Wake at the same time Monday to Sunday, at most an hour later on weekends. If you want more sleep, take a 20-minute nap in the afternoon.
2. Get light as soon as you leave the house. Walk the last stretch of the commute outdoors instead of cutting through the concourse; eat the bagel or breakfast sandwich outside before going into the office.
3. Fix breakfast and lunch times. Eat something within an hour of waking and have lunch at about the same time every day.
4. Dim the lights in the evening. Swap the overhead lights for lamps an hour before bed and mute the work chat.
5. Schedule the most brain-heavy work for the afternoon. While you are adjusting, mornings are still warm-up time, so do not force the hardest decisions first thing.

For Sam, the first week needs one thing: be up before 9 on Saturday and Sunday. Even with a 2 a.m.-ish bedtime on days off, social jet lag would drop from 2 hours 15 minutes to about 1 hour 20 minutes; when the days-off bedtime also moves to around 1 a.m., it approaches 1 hour.

Early birds have a problem too: the late-night hangout and a night-owl partner

Early birds face their own social jet lag in nightlife. When the group chat is still organizing tacos at 1 a.m. or the office dinner drags on to 11, a “little later” on the weekend is a trip abroad for someone who wants to sleep at 10. An early bird can say “I’m asleep by 10” and move the get-together to dinner or brunch. When living with a night-owl partner or roommate, finding the overlap when you are both awake, such as dinner until 9 and weekend noon, works better than asking them to sleep early.