Have you taken one of those online quizzes that assign you an animal based on your sleeping style? According to some, there are four types of sleep animal: wolf, lion, bear and dolphin. But in 2022, Fitbit introduced sleep profiles that identified users as giraffes, bears, dolphins, hedgehogs, parrots or tortoises.
These animals don’t seem to relate to the sleeping habits of the people they’re assigned to – unless those ‘dolphin’ sleepers only allow half of their brains to sleep at any one time, as the mammals do in the wild. You won’t find any of those sleep animals in the scientific literature, though. Only two are generally accepted by the scientists: morning larks and night owls.
These refer to a person’s chronotype, which is their natural preference for sleeping and waking across a 24-hour period. Chronotypes are thought to exist on a spectrum that runs from morning types (larks) to evening types (owls). About 14 per cent of adults are thought to be larks while 21 per cent are owls, with the rest of us falling somewhere between the two.
Studies have shown your cognitive abilities and your energy levels have links to your chronotype, with morning types more energetic and able to perform better on tasks before midday and evening types feeling a gradual increase in energy and ability over the morning and afternoon, before peaking nearer the end of the day.
Understanding your body’s preference can help you plan your days around your natural sleep habits – if you have the ability to tweak the time you start work, for example, or your wake-up time isn’t decided by when your kids get up.
There are genetic factors at play, though. Scientists have identified key ‘clock’ genes that predispose a person’s chronotype toward ‘morningness’ or ‘eveningness’, or neither. But your chronotype is not fixed, like your eye colour.
Large studies have shown that chronotypes change over a lifetime. As children we tend to be early risers, but there’s a sharp rise toward eveningness in teenagers. Then, after the age of about 20, we gradually become more lark-like, until, in our late 50s, we’re getting up and going to bed about the same time we did when we were 10 or 11.
You’re not completely at the mercy of your genetics and your developmental state, however. Your chronotype is heavily influenced by your environment, particularly the amount of light you see at different times of the day. This is because your body clock is constantly taking in information and adjusting your circadian rhythms. This process, known as entrainment, is how we learn to cope with new time zones and why jet lag doesn’t last forever.
Morning light is especially key for setting sleeping patterns. The more morning light you’re exposed to, the more likely you’ll wake earlier the following day, and vice versa. So if you’re prone to sleeping in on a Sunday morning, you’re making it much harder to get up at an earlier time when Monday comes around.
If you fall toward the ‘night owl’ end of the spectrum you can alleviate some of the grogginess of getting up early by exposing yourself to a lot of light in the morning, even if it’s artificial, and by adjusting your workload (where possible) so that the more demanding tasks fall later in the day.
Read more:
- What is sleep inertia?
- Why do we sleep?
- What is worse for your mood – interrupted sleep or shortened sleep?
- Can you ‘bank’ sleep in advance?
Asked by: Esme Newman, via email
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