It is a well-known phenomenon: adolescents tend to suffer from what sleep scientists call “delayed phase” and the rest of us call problems getting out of bed in the morning. And some are more nocturnal than others...
Most teachers are familiar with a pattern: students who stay up late gaming, texting or even reading, have difficulty getting up, and difficulty getting started in the morning. They come into school tired, perhaps irritable. These are the “owls” – left to their own devices (such as in the holidays) they might stay up all night and sleep through to the late afternoon: “vampire hours”. And typically, these owls get poorer grades in school, particularly in subjects such as maths, science and languages.
Owl-hood and grades
Why do owls perform more poorly than their early-rising “larkish” peers? It is tempting to conclude that theirs is a lifestyle choice that simply does not prioritise school work.
Obviously, the habit of staying up late and then getting up at the conventional time for school means that owls are chronically short of sleep. Sleep deprivation has a damaging effect on almost every form of cognitive functioning. The ability to concentrate and reason fades, as does the ability to master new information or learn new skills. This alone might be expected to have an impact on the owl’s school performance, reducing grades.
But there are other factors at work here, too: research shows that owls are generally less conscientious, less motivated to learn, and less possessed of what researchers call “need for cognition” than larks – all of which would contribute to poorer grades, whatever one’s level of fatigue.
In addition, owls are more likely than larks to take drugs – another factor likely to affect school work. Surely all of this is enough to explain the owl’s poor performance? But research suggests that things are not that simple.
For example: a new study in Germany looked at the school performance of owls and larks matched on a wide range of factors – from gender and age to drug-taking, levels of fatigue, conscientiousness, motivation, need for cognition and more. It found that, even when all those factors are taken into account, owls still got significantly poorer grades than larks. In other words, the owl’s disadvantage cannot be wholly explained by their attitudes to school work, outside behaviour nor even by fatigue per se.
This suggests that owls suffer a direct disadvantage in school work, by comparison with larks. And the disadvantage this research identifies lies in the typical school timetable.
Timetabling and performance
Timing matters when it comes to learning. We have long known, for example, that there is a cognitive decline right after eating lunch (the “post-prandial dip”) which makes it harder to study in the early afternoon.
And research is beginning to tease out the ways in which sleep and other processes act to consolidate learning: for example, we know that tasks where there is a strong procedural element, such as mastering a musical instrument or developing a motor skill are learnt best when studied soon before sleeping; while others kinds of task, such as those with a strong verbal element are learnt best much earlier in the day. And we know that the ability to learn is greatly affected by our circadian rhythms.
Anyone who has crossed the Atlantic will know just how hard it can be to perform everyday tasks, let alone learn new ideas or skills, when a change in time zone compels us to be alert when our bodies want to sleep, or to sleep when our bodies are naturally alert. Jet lag involves more than fatigue: it involves trying to function in a world that is fundamentally out of step with one’s circadian rhythm.
What research is showing is that owlish adolescents are living, as it were, in a state of constant jet-lag. Their circadian rhythm is out of step with society, and with the activities society expects of them.
By timetabling lessons as we do, we pose owls with the challenge of learning at a time of day that may be optimal for the lark, but which is far from optimal for the owl. This in itself is enough to place them at a systematic disadvantage.
Who has to change?
One popular explanation of teenage owlishness is that it is a psycho-social phenomenon: part of the general adolescent manoeuvre for separation and independence from the adult world, a re-orientation from parental to peer culture.
Certainly, it is a lifestyle that is strongly supported by a peer culture which favours nocturnal activity, and which can very easily find companionship through the internet at all hours. From this perspective, the owls seem to bring disadvantage on themselves, and the obvious solution is for them to adopt a more sensible sleep pattern.
But even leaving aside the improbability of winning any battle over sleep with a teenager, there are grounds for supposing that the owlish habits of our young are not really under their control.
We have known for a while that there are changes in the circadian pattern of hormones associated with sleep in the teenage years, correlating with the onset of owlish “delayed phase” sleep/wake cycles.
Such correlations can be hard to interpret, as the direction of causality is not always straight-forward when it comes to hormones.
However, a recent study at Ann Arbor University in Michigan may resolve this conundrum: it seems that the owlish sleep shift we see in our teenagers may be a universal feature of human adolescence, occurring across all societies rather than a cultural phenomenon associated with our “24/7” world.
This implies that the adolescent rise in owlishness reflects hormonal changes brought about through the general changes of puberty – in other words, that there is a biological process at work here that is not under the teenager’s voluntary control.
That conclusion is strongly supported by the discovery that there is a shift in circadian patterns matching what we see in human teenagers in other mammal species too.
We may have to accept that teenage “vampire hours” are less a choice and more a natural phenomenon. In which case, it is not the teenager who might have to change, it is the expectations of society.
Practical implications?
School timetabling is fraught with complexity as it is. Should we really be modifying it yet again to address the needs of adolescent owls? And if so, how? The simple thing to do is to shift the school day forward.
Experiments in USA, where schools have shifted the school start from 7:30am to 8:30am have shown clear reductions in both absenteeism and accidents en route to school (American teenagers drive themselves). But this shift from a very early to an early start may not be enough to really match learning to optimal circadian rhythms.
In Britain there has as yet been little exploration of the effects of a later start to the school day, and it is too early to draw firm conclusions from the results. However, schools in Tyneside and London have shifted the start of the school day to 10am (a shift more likely to match teenage circadian rhythms). Early results suggest not only a drop in absenteeism, but an improvement in grades.
Changing the school start is obviously not going to fix all our problems. But who knows what knock-on effects on motivation (and so forth) might emerge, if we relieve the young of the problems of a hormonal jet lag?
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Dr Stephanie Thornton is a chartered psychologist and former lecturer in psychology and child development.