Friday, March 30, 2012

Reader question: “Morning Larks” vs. “Night Owls”: Do certain babies have a preference?

Reader Question: I would love to learn more about how emerging personalities in infancy correlate with later more established adult personalities. One example I know of is that baby sleep patterns (if they are morning larks or night owls) correlate with how they sleep as adults.

What a great question! Today we will start by talking about infant sleep patterns and whether or not they are related to patterns as babies grow older. Then, in a separate post, we’ll consider other aspects of personality, such as temperament, and how they change (or don’t change) over time.

Much of what we know about baby sleep patterns are based on a process that occurs over time as babies’ bodies mature and they become better able to regulate their sleep states (like light and deep sleep) themselves. In the beginning, babies’ sleep patterns are unpredictable and do not follow any particular schedule. As their bodies mature and begin to fall in line with the light/dark cycle, influenced by circadian rhythms, their sleep patterns become more consistent. During the first few months of life it might seem like your baby is a “night owl” because his body doesn’t know yet that nighttime is for sleeping and daytime is for waking. Or he might seem like a “morning person” because he is up in the very early morning hours. All of this is simply because his circadian rhythms are not established. (For a review on early infant sleep, click here.) By about 3 months of age, his body will be able to follow the light/dark cycle like the rest of us.

As babies get older they do have a “natural” time of night when they start to show tired signs and get ready to fall asleep. What’s underneath this natural tendency? The circadian rhythm. The circadian rhythm affects our body temperature, hormone levels, and other bodily functions, all of which affect what time we feel tired and naturally fall asleep and wake up. (For more on circadian rhythms, click here.)

Adult vs. Infant Sleep Patterns

An infant’s sleep patterns are going to look very different from an adult’s sleep patterns. Not only are adult sleep cycles longer, but adults spend more time in deep sleep. Also, children’s sleep patterns are greatly affected by their environment; changes in their routine and surroundings easily disrupt their sleep. (Meltzer & Mindell, 2006) Babies also learn over time how to self-soothe back to sleep after a night waking, whereas adults usually automatically do this. One thing that does stay consistent over time: the length of sleep (duration) that a child gets can be consistent for many years because sleep needs are biologically determined. (Largo 1984) You can try to get them to sleep longer (i.e., put them to bed earlier) but it may cause more night waking, early morning waking, or difficulty falling asleep!

Are Sleep Patterns Hereditary?

One study evaluating the literature related to circadian rhythm sleep disorders revealed that links are just beginning to be made between specific genes and the tendency for “morningness” or “eveningness”. It will be interesting to see what is discovered! (Sack 2007)

The Bottom Line

From the evidence we reviewed, it seems that infants do not have a “preference” for being either “night owls” or ‘morning larks” as some adults do. Though many of us will eventually develop a preference, there is a large variation of sleep times, with “morningness” and “eveningness” at each end of the spectrum.

Stay tuned for part 2 when we will cover personality and temperament similarities as babies grow.


Meltzer LJ, Mindell JA. Sleep and sleep disorders in children and adolescents. Psychiatr Clin North Am. 2006;29(4):1059-76.

Largo RH, Hunziker UA. A developmental approach to the management of children with sleep disturbances in the first three years of life. Eur J Pediatr. 1984;142(3):170-3.

Sack RL, Auckley D, Auger RR, Carskadon MA, Wright KP Jr, Vitiello MV, Zhdanova IV; American Academy of Sleep Medicine. Circadian rhythm sleep disorders: part II, advanced sleep phase disorder, delayed sleep phase disorder, free-running disorder, and irregular sleep-wake rhythm. An American Academy of Sleep Medicine review. Sleep. 2007;30(11):1484-501.

1 comment:

  1. thank you for posting this! i'm the one who asked this question. i LOVE this blog (disclosure: i'm a phd student). doctoral students and scientists have babies, too, right? all the baby blogs and books out there are way too fluffy!