New sleep research

For many years psychologists have divided people into two types based on their sleeping habits. There are Larks who rise early, feel sprightly in the morning, and retire to bed early; and Owls, who do the opposite, preferring to get up late and who come alive in the evening.

Have you ever thought that you don't fit either pattern; that you're neither a morning nor evening person? Even in good health, maybe you feel sluggish most of the time, or conversely, perhaps you feel high energy in the morning and evening. If so, you'll relate to a new study published by Arcady Putilov and his colleagues at the Siberian Branch of the Russian Academy of Sciences.

The researchers invited 130 healthy people (54 men) to a sleep lab and kept them awake for just over 24 hours. The participants were asked to refrain from coffee and alcohol, and several times during their stay they filled out questionnaires about how wakeful or dozy they were feeling. They also answered questions about their sleep patterns and wakeful functioning during the preceding week.

By analysing the participants' energy levels through the 24 period and their reports about their functioning during the previous week, Putilov and his team identified four distinct groups. Consistent with past research, there were Larks (29 of them), who showed higher energy levels on the first and second mornings at 9AM, but lower levels when tested at 9PM and midnight; and there were Owls (44 of them), who showed the opposite pattern. The Larks also reported rising earlier and going to bed earlier through the previous week, whereas the Owls showed the opposite pattern. There was an average two-hour difference between the sleep and wake cycles of these two groups.

The researchers also identified two further chronotypes. There was a "high energetic" group of 25 people who reported feeling relatively sprightly in both the morning and evening; and a "lethargic" group of 32 others, who described feeling relatively dozy in both the morning and evening. Unlike the Owls and Larks, these two groups didn't show differences in terms of their time to bed and time of waking - their habits tended to lie mid-way between the Larks and Owls.

The researchers said their results support the idea of there being "four diurnal types, and each of these types can ... be differentiated from any of three other types on self-scorings of alertness-sleepiness levels in the course of 24-hours sleep deprivation."

We already have bird names for morning and evening people - Owls and Larks. Part of the title of this new paper is "A search for two further 'bird species'". I was hoping the authors might propose two new bird names for their high energy and lethargic categories, but sadly they don't. What about Swift for the high energy category? I'm not sure about a lethargic bird. It's over to you - any ideas? [Readers on Twitter have so far proposed Dodo and Pelican].

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Putilov, A., Donskaya, O., & Verevkin, E. (2015). How many diurnal types are there? A search for two further “bird species” Personality and Individual Differences, 72, 12-17 DOI: 10.1016/j.paid.2014.08.003