There is one study that used diffusion tensor imaging to scan the brains of 20 intermediate chronotypes as well as 16 early-birds and 23 night owls. The study found a reduction in the integrity of the night owl’s white matter in areas of the human brain associated with depression.

Personality chronotypes depend on how alertness and concentration levels vary during the day, or what is known as the concentration curve. Concentration is defined as the amount of time you can focus on a single thought or mental activity. Concentration levels vary depending on who you are with, what you are doing, how interesting it is, and whether you had a nice bottle of wine for lunch!

But, more importantly, concentration and alertness depend on the time of day. For morning larks, alertness and concentration levels start high and decline as the day progresses, while for night owls, this happens in reverse: alertness and concentration levels start low and rise steadily with the passing hours.

Scientists have confirmed that the brain’s internal clock of morning-type people generally runs faster than that of evening-types.

For the morning-type person, alertness levels are normally at their highest in the morning and then start to drop towards the afternoon after a decent lunch, until it reaches its lowest levels in the evening. As the alertness levels drop, the brain’s information processing speed decreases and the internal clock slows down, so time intervals shrink, and time appears to pass quickly. For the morning person, the afternoon is often over in a flash.

With the feeling of abundant time early in the day, morning larks tend to be more productive and can achieve more in the morning than in the afternoon. Therefore, an hour in the morning will generally feel longer than an hour in the afternoon.

The opposite happens for a night-type person. Alertness levels are low in the morning and start to increase towards the afternoon, reaching their highest level in the evening. This means that the brain’s information processing and internal clock start to speed up as the day goes by, so time intervals stretch and time gradually slows down as the day passes. For night owls, mornings fly by and afternoons drag, which makes them more productive in the second half of the day.

If you are interested to find out your chronotype and how that affects your time experience, check out this FREE quick online Speed of Time test that measures how fast time runs inside your brain

For more information on chonotype and time perception, check ‘The Power of Time Perception”

References:

J, Rosenberg et al. “Early to bed, early to rise”: diffusion tensor imaging identifies chronotype-specificity.Neuroimage. 2014 Jan 1;84:428-34

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