The terms "night owl" and "early bird" had been in discussion for centuries before scientists developed the jargon "chronotype" to describe a number of somewhat stable behavioral differences between people. Some people are really morning people who go to bed earlier and do their best in the morning. There are also night owls, and somewhere in between there is a wide range of people. If you live a lifestyle that doesn't fit your chronotype, it leads to what is known as social jet lag, which plays a role from school performance to the frequency of car accidents.
But the "somewhat" part of the "somewhat stable" description of the chronotype is very real. People's chronotypes change with age, and there are signs that they can adapt to everything from exposure to lifestyle.
All of this seems to come together at a fairly important point in people's lives. School usually starts early, which studies have found is good for morning classes. To make matters worse, adolescents usually only notice their chronotype shift later and usually reach a lifelong climax in their late teens. A group of Argentinian scientists has now followed up on what happens to the students' performance if there are differences between the chronotype and the start of school.
A unique resource
As already mentioned, there are indications that the chronotype and the start of school affect the grades of the students. However, all of these studies had one serious limitation: Classes start early almost everywhere. What most of these studies really test is whether early risers do better in school. It is quite possible that an early chronotype may be indirectly linked to other mental characteristics that help improve academic performance. While some studies have found that changing schools later improves grades, starting school later is a bit early for most teenagers who are likely to be at the peak of their nighttime preferences. In other words, studies with students are inevitably carried out at a time when they are suffering from major social jet lag.
(Oddly enough, these studies have shown that affects are subject-specific. A time difference causes problems with math and chemistry, but doesn't appear to have an impact on language or geography.)
The new study manages to cleverly avoid all of this by taking advantage of an extremely rare situation. A school in Buenos Aires offers morning, afternoon and evening courses. Students are randomly assigned to one of these time slots. Thus, the researchers had access to a population of over 750 students, who had very large differences in the way their early school days could match their chronotype. The location has also helped Buenos Aires residents develop a lifestyle in which family dinners typically take place within a few hours after midnight, potentially exacerbating the inconsistencies between chronotypes and different school start times.
The study population included members from all three starting times (around 8:00 a.m., noon, and 5:00 p.m.). There were also two different age groups, a young one that didn't change dramatically into the later hours, and an older one that was right in the middle. All of them were interviewed to find out their chronotype, but were not informed about what the study was investigating.
Tomorrow are the worst
Since the assignment of students was random, one would expect each group to be made up of people with an appropriately random mix of chronotypes. Instead, the researchers found that the morning group had the earliest chronotype of the three, suggesting that the students had managed to adjust to the earlier starts. Older students had average afternoon and evening student chronotypes about an hour later than their younger equivalents based on the measurements used by researchers. For the students of the morning courses, however, it was only a matter of minutes in spite of the great influence of age on this measure.
By comparing student wake-up times on weekends and during school week, the authors estimated the social jet lag that started at the beginning. They found that it was almost four hours for everyone starting in the morning. Even afternoon classes were a little problem for the older students, as they woke up earlier than usual to do other chores in the morning (chores that could have included homework; the researchers didn't). specify t).
As other studies have shown, early schooling was difficult for those students who did not have an early chronotype. With every additional hour of mismatch, the math grades dropped 0.32 points (with a minimum grade of 26). The difference for all other subjects was 0.16 points.
But outside of this, things get complex. In the afternoon classes, there were no differences in performance in chronotypes among younger students who showed no major differences in chronotypes. In older students, the afternoon classes showed no difference in math, but students with an early chronotype performed better in the language. At the evening courses, all chronotypes seemed to run equally well.
Not quite an answer
What does that tell us about chronotypes? The report extends previous results by showing that students benefit on average when the chronotype and school start time are better matched. It's not just about early risers doing better when school starts early. At the same time, the results show that there is never a time of day when the students with the latest chronotype outperform the early birds.
However, there are at least two ways to look at this finding. One is that the early birds have a general academic advantage and get an extra boost if the schedule matches their chronotype. While the latter advantage disappears with increasing chronological deviations, the former remains with them so that they can maintain parity at later school starts. Another way focuses on finding that everyone always has a bit of social jet lag and suggests that people just do a little better in the morning, which offsets the benefits that later chronotypes might have from later school starts.
Why all of this is specific to math is still a mystery.
The difficulty in figuring out exactly what the results tell us is really a sign that we need replications of this work. Even if from a social science point of view it was a large study population, the division by three (starting time at class) and then by two (age group) means that the individual populations examined were still quite small. This could mean that additional clarifying effects are still buried in the statistical noise – or some of the results shown here were wrong.
Despite the considerable uncertainty, the result clearly agrees with previous studies that showed that we are simply going to school at a time when this is disadvantageous for a number of students. While the study shows that students can and can customize their chronotypes to meet early start requirements, there are clearly some students who have trouble doing so.
Nature Human Behavior, 2020. DOI: 10.1038 / s41562-020-0820-2 (About DOIs).