Lack of Willpower or a Night Owl's Clock? What Science Separates Between Chronotype and Procrastination

In 2014, three management researchers published an uncomfortable experiment. Supervisors were asked to rate fictitious employees whose files were identical in every respect but one: some worked from 7 a.m. to 3 p.m., others from 11 a.m. to 7 p.m. Same hours, same performance. The morning workers came out ahead: more conscientious, better at their jobs.

The study, by Kai Chi Yam, Ryan Fehr and Christopher Barnes, did not stay in the lab. In a real company, with pairs of employees and supervisors, they found the same pattern even after accounting for total hours worked, objective performance and the conscientiousness each employee reported about themselves. Starting later made the boss see the person as less conscientious, and that impression dragged their rating down.

Behind that result sits a deeply rooted idea: early risers are disciplined, and people who do their best work at night have a willpower problem. The interesting question is not whether that idea is fair, but how much of it survives the data. Because part of it does.

What the data do show

It would be convenient to start by saying it is all prejudice. It is not.

In 2017, Anastasiya Lipnevich and her team pooled 44 independent samples totaling 16,647 people in a meta-analysis to see how chronotype relates to the Big Five personality traits. The strongest association of all appeared between conscientiousness and morningness, with a correlation of 0.37.

A decade earlier, Nancy Digdon and Andrew Howell had asked 308 Canadian university students about their chronotype, their self-control and their tendency to put off tasks. The more evening-oriented students reported less self-control and more procrastination, with medium-sized correlations.

The relationship exists. But the same meta-analysis contains the figure that changes the reading: the five broad traits together explain only between 10.9% and 16.4% of the differences in chronotype between people. The rest, the vast majority, depends on other things. And this is where three pieces that are almost always presented as one need to be pulled apart.

First piece: a clock nobody chooses

Chronotype has a biological basis. In 2019, a genetic study of 697,828 people from the UK Biobank and the company 23andMe identified 351 regions of the genome associated with being a “morning person.” Using a genetic score built from 292 of those variants, the 5% of people with the strongest morning loading had a sleep phase about 25 minutes earlier than the 5% with the weakest, as measured by activity trackers worn on the wrist.

Twenty-five minutes sounds like little, and for a single person it is. What matters is that the effect exists without anyone having decided anything.

Age adds its own push. Data from some 25,000 people gathered by Till Roenneberg’s team show that chronotype keeps shifting later through adolescence and reaches its latest point at around 19.5 years in women and 20.9 in men. From then on, it gradually moves back toward the morning. That peak is regular enough that the authors proposed it as a biological marker for the end of adolescence.

The story of the caver who spent two months in a cave without a clock tells how researchers discovered that this internal clock runs on its own.

Second piece: the mismatch

A late biological clock would not be a problem in a world that started late. It is one in a world that starts at eight.

In 2006, Marc Wittmann, Till Roenneberg and their colleagues gave that clash a name: social jet lag, the gap between biological time and social time. It is estimated by comparing the midpoint of sleep on free days with the midpoint on workdays. Someone who goes to bed and gets up much later on weekends than during the week is, in practice, taking a small transatlantic flight every Monday.

What that mismatch does to procrastination has been measured day by day. Jana Kühnel, Ronald Bledow and Nicolas Feuerhahn followed 154 employees over five workdays with daily questionnaires. They found three things:

• People procrastinated less on days after they had slept better.
• The greater their social jet lag, the more they procrastinated after a bad night.
• How long they had slept, by contrast, was not related to procrastination.

In other words, the factor was not sleeping more hours, but the quality of rest combined with how far the schedule sat from one’s own clock.

The exam-time test

The cleanest way to separate trait from schedule is to change only the time of day. A school makes that possible.

Vincent van der Vinne, Giulia Zerbini, Thomas Kantermann and their team analyzed 4,734 grades from 741 Dutch students aged 11 to 18, taking into account when each exam had been held. Morning-type students scored significantly better on exams held first thing (from 8:15 to 9:45 a.m.) and in mid-morning (from 10:00 a.m. to 12:15 p.m.). On exams held in the early afternoon, from 12:45 to 3:00 p.m., the difference disappeared.

If the gap between the two groups were purely a matter of character, there would be no reason for it to vanish after lunch.

Two years later, the same group extended the analysis to 40,890 grades from 523 students at a school in the Netherlands. Later chronotypes earned slightly lower grades: 0.06 points less out of 10 for each hour of later chronotype. Between the most morning-oriented 20% and the most evening-oriented 20%, separated by almost three hours of internal clock, the model predicted a difference equivalent to dropping from the 55th to the 43rd percentile. Two caveats do the finding justice: it was the smallest of the study’s significant factors (absences weighed more), and sleep duration was no longer significant once the other variables were taken into account.

Physical and mental performance show the same picture. In a British study of 56 volunteers, Elise Facer-Childs and her team measured reaction time, executive function and grip strength at 2:00 p.m., at 8:00 p.m. and at 8:00 a.m. the next day. At 8:00 a.m., morning types outperformed evening types on all three measures (by 8.4% in reaction time and 5.9% in executive function). At 8:00 p.m., evening types had greater grip strength. Each group performed best in its own time slot.

Third piece: the eye of the beholder

Then there is what the opening experiment showed. Yam, Fehr and Barnes also measured an implicit association: people link the word “morning” more readily than the word “evening” with the idea of conscientiousness. It is a mental shortcut similar to the halo effect, in which one visible trait colors the impression of everything else.

The most revealing detail of the study is who showed that bias. It was stronger among morning-type supervisors and almost disappeared when the supervisor was a night owl. The judgment of other people’s discipline depended, in part, on the clock of the person doing the judging.

A special case: going to bed late

There is one form of procrastination that seems tailor-made for the night owl: putting off bedtime for no external reason. In 2022, Vanessa Hill and her colleagues pooled 43 studies on this phenomenon and found a moderate association with evening chronotype, and also with lower self-control. The authors themselves caution that the quality of the evidence is low and that studies capable of addressing cause and effect are still missing.

The most fine-grained study on the question holds a surprise. Jana Kühnel, Christine Syrek and Anne Dreher followed 108 German employees over a working week. The overall relationship between chronotype and going to bed late did not reach significance. What did emerge was a weekly pattern: evening types delayed their bedtime more on Monday and Tuesday, and from Wednesday on the difference disappeared. What is more, on nights when people felt they had more self-control resources, they put off going to bed more, not less.

That result sits poorly with the lack-of-willpower explanation. It fits better with a clock that arrives at Monday displaced by the weekend and, day by day, readjusts.

The country’s clock counts too

The internal clock synchronizes mainly with sunlight, not with official time. In a study of more than 21,000 people in Germany, Roenneberg’s team found that the average chronotype shifts about 4 minutes later for every degree of longitude to the west, the same time the sun takes to cross it. Between the country’s eastern and western borders, that adds up to about 36 minutes of difference under the same clock time.

Spain is Europe’s most striking case of that distance. A ministerial order dated 7 March 1940, published in the official gazette (BOE) the following day, moved clocks forward one hour from the 16th. It was drafted as a temporary measure, in line with the change France had made on 25 February, and it was never undone. Astronomer Pere Planesas, of Spain’s National Astronomical Observatory, has documented that the story of a gesture toward Nazi Germany does not hold up: Germany did not change its time until April.

The result is that solar noon reaches Vigo at around 1:35 p.m. in winter and around 2:35 p.m. in summer, and in some municipalities in western Galicia the summer gap exceeds two and a half hours, one of the largest in Europe. Next door, Lisbon sees solar noon at around 12:37 p.m. in winter: under roughly the same sun, the two cities are about an hour apart on the clock. Official conclusions have not been unanimous: a parliamentary subcommittee recommended in 2013 returning to Greenwich time, and the government’s expert commission concluded in 2019 that there were not enough reasons to change it. The oft-repeated claim that this is why people in Spain sleep an hour less than the rest of Europe lacks solid scientific backing.

What the data say and what they don’t

What they say	What they don’t say
Morningness is associated with conscientiousness (correlation of 0.37).	That someone’s character can be inferred from their schedule: personality explains less than a sixth of chronotype.
Evening types report somewhat more procrastination on average.	That chronotype causes procrastination: the studies are correlational.
Poor sleep combined with social jet lag is associated with more procrastination the next day.	That the problem is sleeping too few hours: sleep duration was not related.
Evening types’ disadvantage at school shows up in the morning.	That it exists at any hour: on early-afternoon exams it disappeared.
Supervisors tend to see people who start late as less conscientious.	That those people perform worse: in the experiment, performance was identical.
Chronotype has a real genetic basis.	That it is fixed for life: it changes with age and with light.

Three pieces, one result

What research allows us to say with some confidence is more nuanced than the proverb about the early bird. There is a real but modest correlation between chronotype and certain traits. There is a mismatch between clocks that seems to manufacture part of what later gets attributed to character. And there is a social gaze that, without performance data to back it up, rewards the morning.

None of the three pieces makes anyone a better or worse person. Rather, they describe the time of day at which each of us performs best. The chronotype test and the procrastination test help locate oneself on that map, and the article on what chronotype is explains how it is measured. The steady planner and avoidant procrastinator profiles, for their part, describe two very different ways of relating to deadlines.

Sources

• Digdon, N. L. and Howell, A. J. (2008). College students who have an eveningness preference report lower self-control and greater procrastination. Chronobiology International, 25(6), 1029-1046.
• Facer-Childs, E. R., Boiling, S. and Balanos, G. M. (2018). The effects of time of day and chronotype on cognitive and physical performance in healthy volunteers. Sports Medicine - Open, 4, 47.
• Hill, V. M., Rebar, A. L., Ferguson, S. A., Shriane, A. E. and Vincent, G. E. (2022). Go to bed! A systematic review and meta-analysis of bedtime procrastination correlates and sleep outcomes. Sleep Medicine Reviews, 66, 101697.
• Jones, S. E. et al. (2019). Genome-wide association analyses of chronotype in 697,828 individuals provides insights into circadian rhythms. Nature Communications, 10, 343.
• Kühnel, J., Bledow, R. and Feuerhahn, N. (2016). When do you procrastinate? Sleep quality and social sleep lag jointly predict self-regulatory failure at work. Journal of Organizational Behavior, 37(7), 983-1002.
• Kühnel, J., Syrek, C. J. and Dreher, A. (2018). Why don’t you go to bed on time? A daily diary study on the relationships between chronotype, self-control resources and the phenomenon of bedtime procrastination. Frontiers in Psychology, 9, 77.
• Lipnevich, A. A., Credè, M., Hahn, E., Spinath, F. M., Roberts, R. D. and Preckel, F. (2017). How distinctive are morningness and eveningness from the Big Five factors of personality? A meta-analytic investigation. Journal of Personality and Social Psychology, 112(3), 491-509.
• Planesas, P. (2013). La hora oficial en España y sus cambios. Anuario del Observatorio Astronómico de Madrid.
• Roenneberg, T., Kuehnle, T., Pramstaller, P. P., Ricken, J., Havel, M., Guth, A. and Merrow, M. (2004). A marker for the end of adolescence. Current Biology, 14(24), R1038-R1039.
• Roenneberg, T., Kumar, C. J. and Merrow, M. (2007). The human circadian clock entrains to sun time. Current Biology, 17(2), R44-R45.
• van der Vinne, V., Zerbini, G., Siersema, A., Pieper, A., Merrow, M., Hut, R. A., Roenneberg, T. and Kantermann, T. (2015). Timing of examinations affects school performance differently in early and late chronotypes. Journal of Biological Rhythms, 30(1), 53-60.
• Wittmann, M., Dinich, J., Merrow, M. and Roenneberg, T. (2006). Social jetlag: misalignment of biological and social time. Chronobiology International, 23(1-2), 497-509.
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• Zerbini, G., van der Vinne, V., Otto, L. K. M., Kantermann, T., Krijnen, W. P., Roenneberg, T. and Merrow, M. (2017). Lower school performance in late chronotypes: underlying factors and mechanisms. Scientific Reports, 7, 4385.