Sound Cues and Circadian Rhythms

Yesterday, I showed how environmental, behavioral, and social cues act as zeitgebers to human circadian rhythms, and I tried to be as thorough as possible (without outstaying my welcome). I left out one very important environmental cue with the promise of more information today – sound.

I can’t recall exactly where I heard about it, but it was someone’s offhand reference to the notion of the calls of songbirds affecting our circadian rhythms that convinced me I should do a follow-up to the blue light piece from earlier this year. The notion of bird calls affecting us on a deeper level than a regular sound makes some intuitive sense to me, so I did some searching to see if there was anything to it.

There’s certainly a precedent for the phenomenon in animal research. For years, researchers have known that auditory cues exert potent entraining effects on the circadian rhythms of animals. Sounds from a “large animal colony where there were many cats and people,” for example, entrained the circadian rhythms of isolated domestic cats, while common house sparrows’ circadian locomotor rhythms were entrained by the playback of pre-recorded bird song. In squirrel monkeys, the zeitgeber effect of sound cues becomes pronounced when the master pacemaker is partially disabled. So the mechanism clearly exists in certain mammals and birds, but what about humans?

I was only able to find one study, but it’s a good one, and the full text is free. Take a look for yourself.

Ten subjects spent two 4-day lab sessions in constant dim (read: not a significant source of photic entrainment) light. Between 1 AM and 3 AM, before the core body temperature minimum was reached, on the second and third nights of each session, half were subjected to a 2-hour CD of bird calls set to classical music at an intensity equivalent to normal human conversation (this wasn’t blaring. overwhelming noise); the control half were subject to a blank CD they were told contained an auditory stimulus “above the human hearing range.”

Both groups experienced delays in dim light melatonin onset (DLMO) – “a reliable marker of circadian rhythm phase” – and core body temperature (CBT) phases, with the group receiving the auditory stimulus experiencing significantly greater delays. Self-reported feelings of fatigue were also lower in the auditory stimulus group. These results mark the first (and, to my knowledge, only) recorded incidence of auditory cues stimulating circadian phase shifts in humans, “with shifts similar in size and direction to those of other non-photic stimuli” more commonly researched.

Light is the granddaddy of zeitgebers, consistently producing the most amplified phase shifts when compared to non-photic stimuli, but it’s notable that the study’s auditory stimulus produced phase delays that were “consistent in direction with those produced by light.” That is, light input has been shown to induce phase delays (lowered melatonin, delayed “sleepiness” when presented before CBT minimum and phase advances (increased melatonin, advanced “sleepiness”) when presented after CBT minimum. While this study only tested the effect of bird song on circadian phases before CBT minimum, its similarities with light input suggest that bird song might advance the circadian phase if presented post-CBT minimum. That wasn’t tested, though, so we don’t yet know for sure.

Furthermore, most circadian studies of light input employ longer and/or more frequent light pulse durations when compared to the sound study, which may explain the difference in phase shift amplitude. In fact, when you compare this study to studies that use light in similar amounts, the amplitude of circadian phase delay is “of similar magnitude.” It appears as if sound cues have great potential as circadian zeitgebers.

Another question the study’s author raises is whether the source of the sound matters – would we see the same effect on circadian phases if the subjects were presented with a CD playing the soothing sounds of rush hour traffic? Or what if you dropped the classical and kept the bird songs, or vice versa? Is it the mere presentation of auditory stimuli – any auditory stimuli – that matters? Would a two hour conversation with someone else do the trick?

An interesting question, eh? For me at least, it’s not difficult to imagine that specific sounds – like those we would have heard over tens of thousands of years of evolution – may have more of an effect on our millions-of-years-in-the-making circadian rhythms than random, more evolutionarily novel noises. Note that in previous animal studies, researchers were sure to use auditory stimuli that “made sense” to the animals in question: cat sounds for cats and bird songs for birds. As anyone who’s woken up in nature (camping in the mountains, maybe, or deep in the rainforest) can attest, wildlife tends to erect a wall of sound, especially in the morning. You can’t escape it, and any early human ancestors living in the wild would surely have grown up knowing, hearing, and experiencing the sound of birds and other animals on a daily basis.

I mean, we don’t “just wake up.” Hormones, regulated by the circadian clock and entrained by light, sound, and other cues, wake us up.

I don’t usually use an alarm clock. For those rare occasions when I do and as a test, I recently downloaded a new bird chirp ring tone to use as my morning alarm clock instead of the annoying stock tone. I haven’t taken any body temperature or melatonin phase shift measurements, but it certainly is pleasant to wake up to the sound of bird song. This makes me wonder about alarm clocks in general. What’s really happening when we’re awoken by the alarm? I know that the basic shock of a sudden noise (any noise) is what wakes us up initially, but what if a “soothing,” more evolutionarily-congruent sound can make that wake up experience more pleasant and less jarring by shifting our circadian phase, too? Does morning light wake us up through brute, mechanical force, or does it tug at our circadian pacemaker, urging it to produce more cortisol and less melatonin?

This is exciting stuff. Nerdy stuff, sure, but exciting. And, of course, speculative. I’m going to stick with the bird song wake up call and see where it takes me. If anyone else gives it a try (maybe with real birds), let me know how it turns out.

TAGS:  hormones

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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55 thoughts on “Sound Cues and Circadian Rhythms”

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  1. Having just gotten back from a stint in the country, birdsong is definitely a more pleasant and natural way to wake up than say, the alarm clock. Or the garbage truck.

    We were suffering from amazing jet lag and dealing with humid heat (Tuscany in July) and we are both nightowls. So waking up naturally at 5AM was definitely a discrepancy, but a pleasant one. We were in a dark room too, so it was more of an auditory cue than one linked to the sun.

  2. I’d love to see that study with just the birdsong and not the classical music. (Nothing against classical music, it’d just be interesting to adjust that variable.)

    Regardless, birdsong as an alarm clock sound is SUCH an appealing idea. We’ll definitely start trying that!

    It’s light guitar right now, and that first chord is not jarring but by now it immediately elicits a negative reaction from me. I don’t know if that’s wanting more sleep plus familiarity, or what… so maybe a variety of different birdsongs would be the way to go.

    (Of course this would also be easier if I got more sleep, but as a pregnant mom of another baby, that’s a toughie!)

  3. I almost always have birds chirping in my window at approximately 5am and I almost always wake up to them before my alarm goes off. I don’t know if it’s just co-incidence or not but 99% of the time when I wake up naturally, there are birds singing me a song.

    Now if I could just get rid of that crow that squaks at me every-so-often.

  4. When my hubby and I went tent camping couple weeks ago we both forgot our watches.
    I was the first next morning to wake up, noticed it wasn’t pitch dark and wondered what time it is. Tent was in a valley covered by trees so it was hard to guess the time inside the tent without getting up and taking a look outside. Then I heard birds chirping and went “Aha, must be around 6-6:30 a.m.!”

  5. I bird took up residence in a neighbor’s tree this spring and would wake us up in the middle of the night with his calls. Earplugs solved that! 🙂

    I guess I’m not seeing the reproductive advantage in tying our circadian rhythms to sounds like bird song. Maybe because the sooner after sunlight we starting hunting, the more likely we were to catch something? Or is it just that noise indicates there are things to be on the lookout for?

  6. I work shifts that start as early as 5am which means a 4am wake up call or can start later in the day and end at midnight. When I need to set an alarm I wake up to the sounds of church bells on my iPhone. The nice thing about the iPhone alarm is that it starts a little quieter and progresses slightly louder so it is not a noise that startles you awake abruptly, rather something (I feel) you recognize even during sleep and wake more easily without stress. The church bells are standard on the iPhone. The funny thing is sometimes on Sundays I think my alarm is going off later in the day, but it is actually the church a few blocks away.

  7. Here in TN the birds always wake me up. Sometimes too early, if I’ve been indulging in too much blue light the night before.

  8. I downloaded a nature ringtone to my cellphone and use that as my alarm clock. Its pretty cool, starts off real soft and gets louder.

  9. This makes perfect sense. I always wondered why bid calls comforted me and why they were my favorite sound in the morning.

    Now I know there is some scientific stuff to back up my favorite morning workout sound.

    Ken Rogers

    1. Yeah! The birds outside your window in your parents house? They wake you up before going to work??? Oh….wait….

        1. He’s trying to discredit your opinion based on the average American lifestyle compared to yours.

        2. He’s a cyber bully. He decided he does’t like you and he will nag you and make you feel bad. Ignore and never reply or ask Mark to either moderate him or just ban him from posting.

      1. The sunrise wakes me up like I stated Jeff. I then enjoy a wonderfully tasting green smoothie with maybe some eggs. I then take a walk amongst a few other things and then begin working. I do have a job. I just don’t work 9 to 5. I own a business. It seems as if you have a problem with that – the fact that I own a business and am doing everything I possibly can to grow the primal community.

        You may think I make a ton of money which is why you might be angry at me. But, this is entirely untrue. I used to with my eBay business but then AE shut me down. Thankfully I had severe stomach pain for a few days due to gluten in January of this year. Because of that I found this blog which lead me to start my primal blog since I was not enjoying the acne blog anymore.

        I make a few dollars a day yet work up to 8 hours or more in a single day. Why? Because I love what I do. I love blogging about the primal lifestyle. The feedback has been absolutely wonderful which tells me I need to keep doing exactly what I am doing. I will be taking it to the next level within a few days.

        Do I plan on making money with it? Yes. A lot? Well, what’s a lot? All I want to do is help turn around the health of our country and our world. We have been going in the wrong direction for many years but thankfully there are many of us who blog which enables us to connect with millions of people with ease. I am working on the first primal green smoothie e-book. So, yes I will make money. But I will deserve it as I truly work my ass off everyday.

        There are unlimited things I will be doing for the primal community and my passion for it shows on my blog as I have been told many times.

        There is one person in this world that I know does not like me… his name is Jeff. I would love to meet you face to face.

        Sorry for such a long comment Mark… feel free to delete if you wish. I just wanted to let Jeff know whats up. If he wants to learn more then he better say so.

        1. Don’t mind him Todd. He’s just a jealous jerk that’s not happy with his life and takes it out on others for no apparent reason. Continue doing what you love and don’t worry about naysayers. Besides, he’s just a troll.

  10. Take a cue from the new awesome movie called Inception. Use music you love as a kick to wake up. Best way to start your day unstressed.

  11. We sleep with a white noise machine – so i don’t hear the birds but i generally wake up every morning at the same time- 6ish without an alarm clock.

  12. I wake up before dawn nearly every day (and, sadly, have been unable to transition to the alarm-free life). For over a year now, I’ve used a sunrise alarm with a chirping bird track: I almost always wake well before the get-up-and-catch-the-bus alarm on my phone. Makes for a much more pleasant and awake morning.

  13. I wake up way before the birds in my neighborhood. I think the sunrise has more of an effect on my waking than do the birds.

  14. I don’t use alarm clocks to wake up.

    Many years ago, when I would vacation at my parents’, I had to get up very early the day I left to catch a plane. The alarm clock they had gave off a very loud annoying blast.

    I always picked a fight with them before I left. Took me a while to realize it was the alarm clock setting me off.

    I do wake up to birds spring and summer. In the fall they start to leave, and winter is silence (and dark). But I am still able to wake up on a regular basis without an alarm.

  15. I work nights, 3 nights a week. The other nights I’m lucky if I can get to sleep at a decent hour and not sleep half the next day away. I have to use an alarm clock.
    The drone of the AC drowns out any birds, anyway. There was that one morning I woke up with a bird IN the bedroom. That was unsettling (but certainly primal and a whole new take on bringing the outdoors in).

    1. I do shift work as well. It would be interesting to see Mark’s take on shifts and the best way to handle such instances….

  16. As someone who grew up in the wilderness, I agree that waking up to birds chirping is the way to go.

    Whenever most alarm clocks and cell rings wake me up, I immediately go into “fight or flight” mode, with my pulse racing and pores sweating while I try to make sense of all the racket.

    Might have been a good reaction for my caveman forebears to avoid sabre-toothed tigers at night, but it’s just a terrible way for me to start every morning.

    I’ve been thinking about getting one of those alarm clocks that slowly get brighter while heating up aromatherapy oils and playing bird songs. (Yeah, yeah. It’s from the SkyMall catalog. But still!) Anyone try one of these?

    1. We use a dawn clock – it does the light part. You hook it up to a bright light, and it brings it to full light over 20 minutes or so.

      I get very very crabby if I’m woken up by loud noise or commercial radio noise, yelling and commercials.

      Very crabby. 🙂

  17. Good timing. I wake up to a Japaneese song w/ background of birds on my cell alarm. In PRico I used to fall asleep to the sounds of the coqui (frog) & woken up to the sounds of the roosters crowing. My sleeping patterns vary but I’m working on that one.

    1. Roosters crowing… I was never so glad as when my neighbors got rid of theirs. The things apparently had no circadian rhythm as they would always crow somewhere between 3 and 5 am.

      1. I live in suburbia, but down the street someone has a flock of chickens, with one or more roosters. The only thing I can figure is that he’s had them forever and they’ve been grandfathered into the city ordinances. He is surrounded by apartment complexes, so somehow he’s getting around all the complaints. But he’s getting no complaints from me. I LOVE this sound, and I wake up to it every morning. Of course when I had roosters myself, and they were RIGHT OUTSIDE BY BEDROOM WINDOW I was less appreciative.

  18. Although I like the sound of the birds in the a.m. (unless it’s really, really early), my favourite is the robins in the evening just before the sun goes down. Their evening song is different than the one in the a.m., and it just seems like a gentle reminder than it’s time for me to turn in, too.

  19. AMAZING! I never use the air-conditioner, always leaving the windows open on purpose so I can hear the crickets as I sleep and the birds as I wake. Makes too much sense. If only I can switch to reading by candlelight before bed!

  20. Crickets: oh ugg! I’d ask you to imagine me, in the wee small hours, out in my nightclothes in the eastern Washington desert, can of bug spray in hand, trying to track down that one %+&#%&#%&* cricket keeping me awake by driving me nuts…

    Did you know they’re ventriloquists?!? They are NOT located near their crickkking!

    Finally resorted to earplugs…

    The tree frogs bother me too, but less cause it’s not just one of them… that wall of sound thing.

    1. We used to have a hot tub (wood fired) under our bedroom window. The frogs in that tub drove me crazy at night. I had to use earplugs too. They started around ten and continued till after midnight. Fortunately the tub sprang a leak and the water drained out and they went away.

      The wall of sound has been intense this summer: cicadas all day, tree frogs all night. But you sort of get used to it. IT’s like white noise after a while.

      I used to have a rooster too and he started crowing at about 3 am. So much for the cock crow at dawn idea. I gave him away.

  21. Sleeping has been my BIGGEST problem since turning primal a couple of weeks ago. I still can’t get myself to sleep early. Too many digital distractions. It’s just that I work long hours and once I get home, if I’m not gonna work out, I want to unwind with a movie or a video game… Oh well, I’m gonna have to figure it out and sleep when I’m tired.

  22. How about a machine that starts with crickets and frogs(puts me to sleep) and switches gradually to song birds 7 or 8 hours later. When I go to bed an hour after sunrise it is difficult to get to sleep the other way around.

  23. I’ve got an alarm clock that wakes me (on the rare occasions when it’s needed) with light rather than a blaring noise. I really prefer that, though I’ve used a birdsong one that IS pretty nice too. I’ve seen ones that use a gradually increasing chime sound too, which sound like fun.

  24. I dunno. At my old house we had mourning doves. They’d kick in at about 4am or earlier certain times of the year, well before sunrise. It was not at all soothing. Usually I woke in a terrific rage, and wanted nothing more than to go outside, find the offending bird, and stomp on it. And I am not a violent person.

    Perhaps other songbirds would be OK. But I’d take an obnoxious alarm at 7am over a mourning dove at 3:30am any day.

  25. Wow, I tried using a bird song ring tone to wake me up this morning. When I woke up I was convinced it was real birds lol, I just lay there for ages listening. Sadly didn’t get up, switched alarm off, went back to sleep for another 2 hours, however I do feel much better!

  26. I have one of these:

    It’s a ‘sunrise’ type light that gradually comes on to wake you up, but it also gently fades in a sound at the same time. The five or so sampled sounds include a fairly pleasant birdsong loop.

    The sounds could be a bit better, but they’re not bad. It’s a quality product and I find it MUCH more comfortable to wake up to than my old blaring-beep alarm clock! 😉

    (btw I don’t work for Philips or Amazon 😉

  27. Interesting posts, thanks! If this is nerdy stuff, I’m a nerd! With my circadian rhythm disorder, I eagerly read up on this stuff.
    Motto: Early to bed and early to rise will surely lead to an early demise.

  28. I was wonderingif anyone knows the word I’m looking for.? It is not Nocturnal(awake at night) or Diurnal (Awake during day)it is the word for when you are awake at dusk and dawn. Cats are known to follow this pattern. Anyone?

  29. Please contact me at my E-mail cite if you know the word I’m looking for. Thanks, Karen